PC4/PCSK4 is the major Proprotein Convertase (PC) enzyme that plays a key role in mammalian fertilisation. It is detected in the acrosomal granules of round spermatids, acrosomal ridges of elongated spermatids and sperm plasma membrane overlying the acrosome with K-X-K/X-R as its preferred cleavage motif. Such motifs are present in male germ cell proteins ADAMs, proPACAP and proIGF-1/2 and these precursor proteins are processed most likely by PC4 during spermatogenesis, sperm maturation and sperm-egg interaction. For fertilization to occur, the mature sperm must penetrate the Zona Pelucida (ZP) and bind to the egg. Previously, PC4 null mouse sperm and wild type sperm treated with a specific PC4-inhibitor have shown to reduced abilities to penetrate the cumulus mass, bind to ZP and fertilize eggs. These findings suggest that sperm-PC4 plays an important role in fertilization and hence regulation of its activity is crucial for successful fertilization. But how PC4 activity is regulated in vivo is not yet clear. Recently, in epididymal fluid a serpin (serine protease inhibitor) called CRES has been described but the protease linked to this serpin in epididymis has not been identified. However in endocrine cells where CRES is also expressed, it inhibits PC2 enzyme. Thus based on localization and preliminary study, we propose that PC4 is the target enzyme for CRES in the reproductive tract. During sperm migration and storage in epididymis, sperm PC4 activity may be modulated by CRES so that premature sperm activation may not occur. Our data showed that CRES inhibits PC4 both in vitro (with IC50 in µM range) as well as ex vivo in human placenta trophoblast cell lines. Moreover CRES was found to be cleaved by PC4 suggesting a Serpin-Protease binding type of mechanism in the inhibition of protease activity. Taken together, we conclude that CRES regulates PC4 activity in reproductive tract crucial for mammalian fertilization.

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published_or_final_version / Physiology / Master / Master of Philosophy

PC4/PCSK4 is the major Proprotein Convertase (PC) enzyme that plays a key role in mammalian fertilisation. It is detected in the acrosomal granules of round spermatids, acrosomal ridges of elongated spermatids and sperm plasma membrane overlying the acrosome with K-X-K/X-R as its preferred cleavage motif. Such motifs are present in male germ cell proteins ADAMs, proPACAP and proIGF-1/2 and these precursor proteins are processed most likely by PC4 during spermatogenesis, sperm maturation and sperm-egg interaction. For fertilization to occur, the mature sperm must penetrate the Zona Pelucida (ZP) and bind to the egg. Previously, PC4 null mouse sperm and wild type sperm treated with a specific PC4-inhibitor have shown to reduced abilities to penetrate the cumulus mass, bind to ZP and fertilize eggs. These findings suggest that sperm-PC4 plays an important role in fertilization and hence regulation of its activity is crucial for successful fertilization. But how PC4 activity is regulated in vivo is not yet clear. Recently, in epididymal fluid a serpin (serine protease inhibitor) called CRES has been described but the protease linked to this serpin in epididymis has not been identified. However in endocrine cells where CRES is also expressed, it inhibits PC2 enzyme. Thus based on localization and preliminary study, we propose that PC4 is the target enzyme for CRES in the reproductive tract. During sperm migration and storage in epididymis, sperm PC4 activity may be modulated by CRES so that premature sperm activation may not occur. Our data showed that CRES inhibits PC4 both in vitro (with IC50 in µM range) as well as ex vivo in human placenta trophoblast cell lines. Moreover CRES was found to be cleaved by PC4 suggesting a Serpin-Protease binding type of mechanism in the inhibition of protease activity. Taken together, we conclude that CRES regulates PC4 activity in reproductive tract crucial for mammalian fertilization.

Orientador: Frederico Ozanam Papa / Banca: Marco Antonio Alvarenga / Banca: Fabiana Ferreira de Souza / Resumo: A recuperação de espermatozóides da cauda do epidídimo e sua criopreservação pode ser a última chance para recuperação do material genético quando ocorre morte súbita ou lesão grave em garanhões de alto valor genético. Sendo assim, o objetivo do experimento I foi comparar os parâmetros espermáticos dos espermatozóides da cauda do epidídimo recuperados imediatamente após orquiectomia e em diferentes momentos após armazenamento a 5°C e a temperatura ambiente. Já o experimento II, teve o objetivo de comparar os parâmetros espermáticos e fertilidade dos espermatozóides do ejaculado e do epidídimo recuperados logo depois da orquiectomia e após armazenamento por 24 horas a 5°C. No experimento I, 48 garanhões foram submetidos à orquiectomia bilateral, sendo que em oito a colheita dos espermatozóides do epidídimo foi realizada imediatamente após orquiectomia (grupo controle). Nos outros 40 garanhões, um epidídimo foi armazenado a temperatura ambiente e o contralateral armazenado a 5°C por 6, 12, 18, 24 e 30 horas, de acordo com o grupo. No experimento II, dois ejaculados de oito garanhões foram colhidos com vagina artificial e congelados (grupo EJ-0h). Uma semana após, os garanhões foram submetidos à orquiectomia bilateral, sendo que os espermatozóides de um epidídimo foram congelados imediatamente após orquiectomia (grupo EP-0h) e o epidídimo contralateral foi previamente armazenado por 24 horas a 5°C (EP-24h). O teste de fertilidade demonstrou que o grupo EP-0h (92,3%; n=13) tendem a ser maior que os grupos EJ-0h (61,5%; n=13) e EP-24h (61,5%; n=13). Conclui-se que o armazenamento dos testículos-epidídimos a 5°C proporcionou melhor preservação espermática e que, independente da temperatura, a motilidade progressiva é o parâmetro espermático mais sensível ao tempo de armazenamento. / Abstract: Cauda epididymis sperm recovery and cryopreservation may be the last chance to obtain genetical material when sudden death or serious injury occur in valuable stallions. Thus, the aim of experiment I was to compare sperm parameters of epididymal sperm recovered immediately after orchiectomy and at different moments after storage at 5°C and at room temperature. Experiment II aimed to compare sperm parameters and fertility of ejaculated sperm and epididymal sperm recovered immediately after orchiectomy and after storage for 24h at 5°C. In experiment I, 48 stallions were submitted to bilateral orchiectomy, in eight of those the sperm collection were done immediately after orchiectomy (control group). In the other 40 stallions, one epididymis was stored at room temperature and the other was stored at 5°C for 6, 12, 18, 24 and 30 hours accorded to groups. In experiment II, two ejaculated from eight stallions were obtained with artificial vagina and cryopreserved (group EJ-0h). One week later, the stallions were submitted to bilateral orchiectomy, and the sperm of one epididymal were frozen immediately after orchiectomy (group EP-0h) and the contralateral epididymal was previously storage for 24h at 5°C (EP-24h). Fertility test showed that group EP-0h (92,3%; n=13) tended to be higher than groups EJ-0h (61,5%; n=13) and EP-24h (61,5%; n=13). These results allowed concluding that storage of the testis-epididymis complex at 5°C is more efficient in preserving sperm parameters than room temperature storage and that progressive motility is the parameter that is more affected by storage period, regardless of the temperature. / Mestre

abstract: Infertility has become an increasing problem in developed countries and in many cases can be attributed to compromised sperm quality. Assessment of male fertility typically utilizes semen analysis which mainly examines sperm morphology, however many males whose sperm appear normal are sub- or infertile, suggesting that sperm from these males may be deficient in a protein or suite of proteins. To date, very little is known about the composition of sperm or the complex maturation process that confers motility and fertilization competency to sperm. Chapter 1 discusses the use of whole cell mass spectrometry to identify 1247 proteins comprising the Rhesus macaque (Macaca mulatta) sperm proteome, a commonly used model of human reproduction. This study provides a more robust proxy of human sperm composition than was previously available and facilitates studies of sperm using the rhesus macaque as a model. Chapters 2 & 3 provide a systems level overview of changes in sperm proteome composition that occurs during epididymal transit. Chapter 2 reports the proteomes of sperm collected from the caput, corpus and cauda segments of the mouse epididymis, identifying 1536, 1720 and 1234 proteins respectively. Chapter 3 reports the sperm proteome from four distinct segments of the Rhesus macaque epididymis, including the caput, proximal corpus, distal corpus and cauda, identifying 1951, 2014, 1764 and 1423 proteins respectively. These studies identify a number of proteins that are added and removed from sperm during epididymal transit which likely play an important role in the sperm maturation process. To date no comparative evolutionary studies of sperm proteomes have been undertaken. Chapter 4 compares four mammalian sperm proteomes including the human, macaque, mouse and rat. This study identified 98 proteins common to all four sperm proteomes, 82 primate and 90 rodent lineage-specific proteins and 494, 467, 566, and 193 species specific proteins in the human, macaque, mouse and rat sperm proteomes respectively and discusses how differences in sperm composition may ultimately lead to functional differences across species. Finally, chapter 5 uses sperm proteome data to inform the preliminary design of a rodent contraceptive vaccine delivered orally using recombinant attenuated Salmonella vaccine vectors. / Dissertation/Thesis / Ph.D. Biological Design 2013

Orientador: Luis Antonio Violin Dias Pereira / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-10T03:55:25Z (GMT). No. of bitstreams: 1 Arroteia_KelenFabiola_D.pdf: 15193315 bytes, checksum: b6b3930ea05ff1d7b858f560e01c178a (MD5) Previous issue date: 2006 / Resumo: O processo de fecundação em mamíferos depende de uma seqüência de eventos que culminam na ativação do oócito pelo espermatozóide. A diferenciação completa das células germinativas testiculares em células com capacidade fecundativa envolve testículos, epidídimos, ductos deferentes e trato reprodutor feminino. No epidídimo, a superfície dos espermatozóides pode sofrer diversas modificações, em um processo conhecido como maturação epididimária. Diversas proteínas sintetizadas e secretadas pelas células epiteliais do epidídimo serão posteriormente localizadas na superfície ou mesmo no interior da vesícula acrossômica do espermatozóide. A aquisição da capacidade de fertilização pelo spermatozóide tem sido correlacionada à esta nova organização das moléculas de membrana proporcionada durante o trânsito epididimário. A obtenção de anticorpos monoclonais que reconhecem os antígenos expressos pelas células germinativas testiculares durante seus processos contíguos de diferenciação, ou pelas células dos ductos pelos quais os espermatozóides transitam durante o processo de maturação tem constituído uma importante estratégia para permitir a geração de um mapa das moléculas que atuam na preparação do espermatozóide para a fecundação. O anticorpo monoclonal (Amc) TRA (testicular germ cells immunized to rat - monoclonal antibody) 54 reconhece um antígeno localizado em espermátides dos túbulos seminíferos de camundongos C57 BL/6 com idade superior a 24 dias pós-parto e também um antígeno expresso nas células epiteliais da cabeça do epidídimo e em espermatozóides da luz deste órgão. A molécula secretada percorre a luz do epidídimo no sentido ântero-posterior e, neste percurso, é incorporada pelos espermatozóides em trânsito. Com o intuito de contribuir para a compreensão dos complexos mecanismos que preparam o espermatozóide para a fecundação, o presente trabalho buscou identificar e reconhecer a estrutura protéica e a função biológica do antígeno reconhecido pelo Amc TRA 54 nas células epiteliais do epidídimo. No futuro, os resultados obtidos poderão contribuir com a geração de novas ferramentas clínicas para a solução de problemas relacionados à biologia da reprodução / Abstract: In mammals, fertilization depends on a sequence of events that culminates in the activation of the oocyte by the spermatozoa. The complete differentiation of the testicular germ cells in cells with fertilization ability involves the testis, epididymis, vas deferens and female reproductive organs. In the epididymis, the membrane surface of the spermatozoa may be modified, through a process known as epididymal maturation. Several proteins synthesized and secreted by the epididymal epithelial cells can be further located on the spermatozoa membrane surface or even though inside its acrosomal vesicle. The acquisition of the fertilization ability by the spermatozoa has been related with a new molecular organization of the membrane provided during the epididymal transit. The production of monoclonal antibodies (mAb) that recognizes antigens exclusively expressed by testicular germ cells or by the cells of the ducts through the spermatozoa passes during its maturation has been considered an important approach to permit the elaboration of the molecular map involved in the spermatozoa preparation. The mAb TRA (testicular germ cells immunized to rat - monoclonal antibody) 54 recognizes an antigen located in spermatids of seminiferous tubules of C57 BL/6 mice more than 24 days old and also in a specific population of epithelial cells in epididymal caput and in the luminal spermatozoa. The synthesis and release of the epididymal antigen occur in an androgen-dependent manner and independent of the testicular expression. Released antigen moves down the epididymis and is further incorporated by luminal spermatozoa. This work was performed in order to comprehend the complex mechanisms that prepare spermatozoa for the fertilization process. The molecular structure of the epididymal protein and its biological functions were investigated and solved. In a near future, the obtained results can contribute with new clinical tools for solving problems in reproductive biology / Doutorado / Histologia / Doutor em Biologia Celular e Estrutural

Submitted by Natalia de Souza Gonçalves (natalia.goncalves@ufpe.br) on 2016-09-15T14:49:54Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) NIVALDO BERNARDO DE LIMA JUNIOR_PROGRAMA DE PÓS-GRADUAÇÃO EM SAÚDE HUMANA E MEIO AMBIENTE_CENTRO ACADÊMICO DE VITÓRIA_2016.pdf: 3049237 bytes, checksum: 3c055666b0821330db98ccf2d17c644b (MD5) / Made available in DSpace on 2016-09-15T14:49:54Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) NIVALDO BERNARDO DE LIMA JUNIOR_PROGRAMA DE PÓS-GRADUAÇÃO EM SAÚDE HUMANA E MEIO AMBIENTE_CENTRO ACADÊMICO DE VITÓRIA_2016.pdf: 3049237 bytes, checksum: 3c055666b0821330db98ccf2d17c644b (MD5) Previous issue date: 2016-02-24 / CAPES / Dermanura cinerea é um morcego frugívoro, cujas informações acerca da sua biologia reprodutiva ainda permanecem pouco conhecidas em diferentes biomas do Brasil, sobretudo quando se considera as análises morfométricas e histológicas de suas gônadas. O objetivo desse trabalho foi analisar por meio do estágio reprodutivo, histologia e morfometria o testículo, epidídimo e ovário de D. cinerea, ao longo do ciclo reprodutivo anual, em um fragmento preservado de Mata Atlântica (Reserva Biológica de Saltinho) situado no estado de Pernambuco, Nordeste do Brasil. Fêmeas e machos adultos foram capturados por meio de redes de neblina e as coletas ocorreram mensalmente, durante duas noites consecutivas, ao longo de dezoito meses. Os dados meteorológicos foram agrupados em seis períodos de três meses cada: período I (junho – agosto/2014); período II (setembro – novembro/2014); período III (dezembro/2014 – fevereiro/2015); período IV (março – maio/2015); período V (junho – agosto/2015) e período VI (setembro – novembro/2015). Esse agrupamento foi realizado com base no que se tem descrito para o período seco (setembro - fevereiro) e período chuvoso (março - agosto) nessa área de estudo. Entretanto, alguns meses apresentaram médias de precipitação atípicas entre os períodos, enquanto a temperatura teve pouca variação (24,0 a 27,4). Foram capturados um total de 23 machos e 25 fêmeas. Os testículos dos machos foram classificados de acordo com a morfologia externa em: machos com testículos descendentes e não descendentes. Já as fêmeas foram classificadas em: inativas, grávidas, lactantes e pós-lactantes. Os espécimes utilizados nas análises histomofométricas dos órgãos foram eutanasiados. Nos machos foram selecionados 18 espécimes, ao passo que nas fêmeas foram selecionadas 10 inativas. Os órgãos foram coletados, fixados e processados seguindo a técnica histológica de rotina. As lâminas histológicas produzidas foram coradas por Hematoxilina – Eosina e analisadas em microscópio óptico. Morfometricamente, nos testículos, foram realizadas mensurações da área de ocupação do compartimento tubular e intertubular, número de células de Leydig, de Sertoli, de espermatócitos e de espermátides alongadas. No epidídimo foi mensurada a altura do epitélio, o diâmetro tubular, diâmetro do lúmen e diâmetro do epitélio das regiões do segmento inicial, cabeça, corpo e cauda. No ovário foi mensurada as áreas total e de ocupação dos folículos em diferentes estágios de maturação, incluindo a quantificação destes folículos e corpo lúteo. Esses dados foram submetidos ao teste t de Student. De acordo com os resultados, a atividade testicular de D. cinerea não apresenta um padrão reprodutivo definido; o epidídimo possui maior sensibilidade às variações sazonais na região caudal e as fêmeas apresentam dois picos reprodutivos de acordo com os períodos considerados em área de Mata Atlântica do estado de Pernambuco. / Dermanura cinerea is a fruit bat, whose information about their reproductive biology are still little known in different biomes of Brazil, especially when considering the morphological and histological analyzes of their gonads. The aim of this study was to analyze through the reproductive stage, histology and morphometry the testis, epididymis and ovary of D. cinerea, during the annual reproductive cycle in a fragment preserved Atlantic Forest (Biological Reserve Saltinho) located in the state of Pernambuco, northeastern Brazil. Adult females and males were captured through nets and the collections were monthly during two consecutive nights along eighteen months. Meteorological data were grouped into six periods of three months each: period I (June - August / 2014); period II (September - November / 2014); period III (December / 2014 - February / 2015); period IV (March - May / 2015); period V (June - August / 2015) and period VI (September - November / 2015). This grouping was based on what has been described for the dry season (September - February) and rainy season (March - August) in this study area. However, a few months have mean atypical precipitation between the periods while the temperature had little variation (24.0 to 27.4). A total of 23 males and 25 females were captured. The testes of males were classified according to the external morphology: males with descendant testes and not descendant. The females were classified as inactive, pregnant, lactating and post-lactating. Specimens used in histomorphometric analysis of the organs were euthanized. In males were selected 18 specimens, while females were selected in 10 inactive. The bodies were collected, fixed and processed according to routine histological technique. The produced histological slides were stained with hematoxylin - eosin and analyzed by light microscopy. Morphometrically in the testes were performed measurement of the occupation area tubular compartment and Intertubular, number of Leydig cells, Sertoli cells, spermatocytes and spermatids elongated. In the epididymis was measured the height of the epithelium, the tubular diameter, lumen diameter and diameter epithelial of the regions of the initial segment, caput,corpus and cauda. Ovary was measured and the total areas of occupation of follicles at different stages of maturation, including quantification of these follicles and corpus luteum. These data were submitted to Student's t test. According to the results, testicular activity D. cinerea does not present a defined reproduction pattern; the epididymis is more sensitive to seasonal variations in the flow region and the females have two reproductive peaks according to the periods considered in Atlantic Forest area of the state of Pernambuco.

Orientadores: Luis Antonio Violin Dias Pereira, Suzana de Fatima Paccola Mesquita / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-20T22:34:25Z (GMT). No. of bitstreams: 1 Garcia_PatrickVianna_D.pdf: 2682268 bytes, checksum: c80303a2f196fc3cdb21e73865600ba4 (MD5) Previous issue date: 2012 / Resumo: Durante o processo de maturação epididimária, proteínas secretadas pelo epidídimo interagem com os espermatozoides modificando-os funcionalmente. Cerca de 75% das proteínas que participam da maturação epididimária são secretadas pelas células epiteliais do segmento inicial e cabeça do epidídimo e 48% destas proteínas tem a síntese dependente de dihidrotestosterona (DHT), a qual é sintetizada a partir da testosterona pela ação da enzima 5 ? redutase. A DHT é de extrema importância para a fisiologia do sistema reprodutor masculino. Níveis elevados de DHT na vida adulta podem predispor a vários distúrbios, tais como a alopecia androgênica. Com o intuito de se minimizar os efeitos da DHT, a finasterida foi o primeiro inibidor da 5 ? redutase que recebeu aprovação clínica para o tratamento desses distúrbios.Um público cada vez mais jovem utiliza a finasterida como um método preventivo e paliativo contra a alopecia androgênica, com isso, estudos dos efeitos da finasterida no sistema reprodutor masculino são de grande interesse clínico. O ojetivo desse estudo foi avaliar as possíveis alterações no segmento da cabeça do epidídidmo e na qualidade espermática em animais submetidos ao tratamento agudo (15 dias), crônico (56 dias) e animais que tiveram o tratamento (agudo e crônico) interrompido por um período de 30 dias. Na administração aguda (15 dias) de finasterida em ratos observou-se algumas alterações na integridade da membrana plasmática do espermatozoide. A administração crônica (56 dias) de finasterida em ratos leva a alterações no epidídimo, tais como: redução do peso, alterações morfométricas-estereológicas, diminuição do tempo de trânsito do espermatozoide, redução da motilidade, alterações na integridade da membrana do espermatozóide e redução nos parâmetros de fertilidade desses animais. Mesmo com a interrupção do tratamento com finasterida (por 30 dias) a qualidade do espermatozóide continua comprometida. Dessa forma, estudos adicionais devem ser realizados para complementar o conhecimento existente sobre a fisiologia do epidídimo após a depleção DHT, sobre o tempo que necessário para a recuperação dos parâmetros de fertilidade após a interrupção do tratamento com finasterida, e se estes parâmetros podem ser totalmente recuperados / Abstract: During epididymal maturation, proteins secreted by epididymis functionally interact with the spermatozoa modifying it. About 75% of the proteins that participate in the epididymal maturation are secreted by the epithelial cells of the initial segment and caput of the epididymis and 48% of the synthesis is dependent on dihydrotestosterone (DHT), which is synthesized from testosterone by the action of the enzyme 5 ? reductase.The DHT is extremely important for the physiology of the male reproductive system. High levels of DHT in adulthood may predispose to various disorders such as androgenic alopecia. In order to minimize the effects of DHT, medications were produced with the purpose of inhibit the action of 5 ?-reductase and among those medications the finasteride was the first 5 ? reductase inhibitor that received clinical approval for the treatment of these disorders. A public increasingly young uses finasteride as a preventive and palliative method and against androgenic alopecia, in this way; studies of the effects of finasteride in the male reproductive system are of clinical and commercial interest. The aim of this study was to evaluate the possible alterations in the caput epididymis and sperm quality in animals submitted to acute (15 days) and chronic (56 days) treatment and animals with 30 days post- treatment. Acute administration of finasteride in rats (15 days) was observed reduction in sperm membrane integrity. Chronic administration of finasteride in rats (56 days), leads to changes in the epididymis, such as weight reduction, morphometric-stereological changes, decreased transit time of sperm, motility of the sperm membrane integrity and consequently in fertility parameters of these animals. Even with the interruption of treatment with finasteride (30 days) sperm quality remains committed. Thus, further studies should be performed to complement the existing knowledge on the physiology of the epididymis after DHT depletion, on the time that is needed for the recovery of fertility parameters after interruption of finasteride treatment, and if it these parameters can be fully recovered / Doutorado / Histologia / Doutor em Biologia Celular e Estrutural

Melatonin is a product of the pineal gland and is postulated to play an antigonadotropic role in the reproductive system of mammals. The reproductive system of non-seasonally breeding mammals is believed to be not as responsive to melatonin treatment as that of seasonally breeding mammals. Recently, there has been increasing support from in vivo and in vitro studies, for the hypothesis that melatonin has negative effects on sperm physiology, especially on sperm motility. High and/or low seminal concentrations of melatonin have been associated with abnormalities in human sperm motility and concentration. In this study, I examined the effects of melatonin on the testis, epididymis and sperm physiology, using in vivo and in vitro experiments, in a non-seasonally breeding mammal. Treatment, in vivo, with exogenous melatonin for six weeks did not inhibit testosterone production or spermatogenesis, nor did it affect the mass of the testes and epididymides at dissection, the concentration the morphology of speimatozoa. However, melatonin in vivo had a small, but significant negative effect on sperm motility and sperm motility index. In vitro incubation of spermatozoa Fith melatonin reduced the percentage (%) of forward progressive movement (fpm), increased the % reduction in fpm, reduced the vigor or quality of sperm motility, reduced the sperm motility index, and delayed and/or prolonged the transition of one pattern of sperm motility to the subsequent patterns. Melatonin increased the pH of the culture medium, and the increased pH, and the ethanol utilized as a solvent for melatonin, both negatively affected all the sperm motility parameters that were assessed in my study. The effects of ethanol increased with time, and the effects of pH increased with both time and increasing pH. Melatonin in vitro did not inhibit capacitation and the acrosome reaction, but it delayed the onset and the progression of capacitation and the acrosome reaction. These results suggest that while melatonin did not inhibit spermatogenesis in the Wistar rat, it may influence sperm motility. Therefore, the presence of high concentrations of melatonin in the reproductive fluids may inhibit sperm motility. With further detailed research, melatonin may have a potential use as a contraceptive drug.