Hemos inducido en ratas wistar dos modelos de hipertensión arterial (HTA): hipertensión vasculorrenal 2 riñones-1 clip (2R-1C) e hipertensión por déficits crónico de óxido nítrico (NO). La angiotensina II (AII) participa en el desarrollo y mantenimiento de la hipertensión vasculorrenal y por déficit crónico de NO. La administración crónica de losartán, aún previniendo el desarrollo de la hipertensión por déficit crónico de NO, no confiere protección completa frente a las alteraciones hemodinámicas que dicha hipertensión conlleva. Los bloqueantes de los receptores de la AII, saralasina y losartán, poseen efectos hemodinámicos similares, aunque de distinta potencia, sobre los grupos de HTA. En condiciones normales, los efectos hemodinámicos del péptido natriurético auricular (PNA) no son modulados por los receptores de AII. La HTA potencia los efectos hemodinámicos del PNA por un efecto en el que intervienen los receptores de AII. / We have induced in Wistar rats two models of experimental hypertension: two kidney-one clip hypertension (2K-1C) and hypertension induced by chronic inhibition of nitric oxide production (L-NAME-induced hypertension). In both, angiotensin II (AII) participates in the development and maintenance of the hypertension. Chronic administration of losartan prevents the development of the L-NAME-induced hypertension, although it does not confer complete protection to the hemodynamic alterations that this hypertension causes. The AII receptor antagonists, saralasin and losartan, have similar hemodynamic effects on the hypertensive groups, although in different degrees. Moreover, the hemodynamic effects of the atrial natriuretic peptide (ANP) under normal conditions are not modulated by the AII receptor. However, hypertension increases the hemodynamic effects of the ANP by an effect partially due to the AII receptors

Abstract Cardiovascular diseases are the leading causes of death in the developed countries and their incidence is not expected to decrease in the future. There is a lifetime risk of one in five of developing heart failure, which still has poor prognosis and current treatments only cover part of the pathophysiology behind this syndrome. Pathological processes contributing to heart failure include cardiac hypertrophy and remodeling, which involves neurohumoral activation, reactivation of fetal genes, impaired Ca2+ cycling, increased apoptosis, and increased fibrosis. Intracellular signalling pathways and transcription factors mediating the response to various extracellular stresses have a key role in the regulation of myocardial remodeling and they are investigated in order to develop new approaches for the treatment of heart failure. The aim of this thesis was to elucidate roles of mitogen-activated protein kinases (MAPKs) and transcription factor GATA-4 in the regulation of cardiomyocyte function in cell cultures, and in hearts ex vivo and in vivo. The main findings were that (i) Inhibition of p38α MAPK enhanced function of sarco/endoplasmic reticulum Ca2+ -ATPase and thus cardiac contractility by increasing phosphorylation of protein phosphatase inhibitor-1 and phospholamban, (ii) p38 MAPK isoforms p38α and p38β regulated promoter activity of B-type natriuretic peptide via distinct pathways, (iii) p38α and p38β MAPKs also had different effects on gene expressions related to fibrosis and hypertrophy, and (iv) p38 and ERK1/2 MAPKs mediated stretch-induced activation of GATA-4 by phosphorylation at Ser 105. GATA-4 also seems to be regulated by ubiquitination. This study provides novel data of p38 MAPK and GATA-4 in the regulation of cardiomyocyte function. Inhibition of p38α MAPK could be beneficial in the treatment of heart failure. Also GATA-4 is a potential target for treatment of cardiovascular diseases. / Tiivistelmä Sydän- ja verisuonisairaudet ovat yleisin kuolinsyy länsimaissa, eikä niiden ilmaantuvuus tule vähenemään lähitulevaisuudessa. Elinikäinen riski sairastua sydämen vajaatoimintaan on 20 %, ja sydämen vajaatoiminnan ennuste on edelleen huono. Nykyisillä hoitomuodoilla voidaan puuttua vain osittain sydämen vajaatoiminnan patofysiologisiin mekanismeihin. Sydämen vajaatoiminnan kehittymiseen liittyvät sydänlihaksen liikakasvu ja uudelleenmuovautumisprosessi, johon liittyy neurohumoraalinen aktivaatio, sikiöaikaisten geenien uudelleenilmentyminen, häiriöt solunsisäisessä Ca2+-viestinnässä sekä lisääntynyt ohjelmoitu solukuolema ja sidekudoksen muodostuminen sydämeen. Solunsisäisillä viestinvälitysketjuilla sekä transkriptiotekijöillä, jotka vastaavat solunulkoisten ärsykkeiden välittämisestä solun sisällä, on keskeinen rooli edellämainittujen prosessien säätelyssä. Uusien lähestymistapojen kehittäminen sydämen vajaatoiminnan hoitoon edellyttää myös solunsisäisen viestinvälityksen ja geenien säätelyn mekanismien selvittämistä. Tämän väitöstyön tavoite oli selvittää p38 mitogeeniaktivoituvan proteiinikinaasin (p38 MAPK) ja transkriptiotekijä GATA-4:n merkitystä sydämen vajaatoiminnan patogeneesissä soluviljelymalleissa. Päälöydöksiä olivat: (i) p38α MAPK -isoformin estäminen paransi kalsiumia solulimakalvostoon pumppaavan SERCA2a:n toimintaa ja sydänlihassolun supistumiskykyä lisäämällä fosfolambaanin ja proteiinifosfataasi-inhibiittori-1:n fosforylaatiota. (ii) p38 MAPK isoformit p38α ja p38β säätelivät B-tyypin natriureettisen peptidin geenin promoottorialuetta erillisten reittien kautta. (iii) p38α ja p38β isoformit vaikuttivat myös eri tavoin sydämen sidekudoksen muodostumiseen ja hypertrofiaan liittyvien geenien ilmentymiseen. (iv) p38 ja ERK1/2 välittävät venytyksen aiheuttaman GATA-4:n aktivaation fosforyloimalla seriini-105 fosforylaatiopaikan. Lisäksi GATA-4:n toimintaa säädellään ubiquitinaation avulla. Tämä tutkimus tuo uutta tietoa p38 MAPK:n ja GATA-4:n rooleista sydämen vajaatoiminnan kehittymisessä. p38α-isoformin toiminnan estäminen voisi olla hyödyllinen hoitomuoto sydämen vajaatoiminnassa. Myös GATA-4 on potentiaalinen lääkehoidon kohde sydänsairauksien hoidossa.

<p>Kardijalni biomarkeri u predviđanju operativnog rizika kardiohirur&scaron;kih bolesnika sa oslabljenom sistolnom funkcijom leve komore Evaluacija rezultata u kardiohirurgiji podrazumeva praćenje ishoda operativnog lečenja u određenom vremenskom periodu. Najče&scaron;će je to interval od 30 dana od datuma intervencije. Najče&scaron;ći kriterijumi za praćenje su stopa mortaliteta i morbiditeta, dužina boravka u jedinici intenzivnog lečenja, ukupna dužina hospitalizacije i tro&scaron;kovi lečenja. Stratifikacija rizika podrazumeva da se bolesnici mogu podeliti u grupe u zavisnosti od broja i važnosti preoperativno utvrđenih faktora rizika, odnosno da se pre operacije može predvideti ishod hirur&scaron;ke intervencije kod svakog od njih pojedinačno. U Evropi je, u periodu između 1995. i 1999. godine, na osnovu multicentrične studije u 8 evropskih zemalja i 128 kardiohirur&scaron;kih centara u kojima je operisano 19.030 odraslih bolesnika, kreiran EvroSKOR - EuroSCORE (European System for Cardiac Operative Risk Evaluation) model za stratifikaciju rizika u kardiohirurgiji. Međutim, neminovne promene i napredak u operativnom lečenju doveli su do toga da je neophodno ažurirati postojeći sistem stratifikacije. Tako je 2012. godine u rutinsku upotrebu uveden novi sistem Euroscore II. Na Klinici za kardiohirurgiju Instituta za kardiovaskularne bolesti Vojvodine (IKVBV), EuroSCORE model uveden je u rutinsku upotrebu od početka 2001. godine. Analizom rezultata, posle dvogodi&scaron;nje primene, pokazalo se da je model bio precizan, odnosno da nije postojala značajna razlika između očekivanog (3,7%) i stvarnog mortaliteta (3,47%). U poslednjih nekoliko godina, kod bolesnika kojima sledi kardiohirur&scaron;ka intervencija, u smislu razmatranja njihove prediktivne vrednosti, sve vi&scaron;e pažnje se poklanja kardijalnim biomarkerima. Najznačajniji biomarkeri u kardiovaskularnoj medicini su: Troponin, Kreatin kinaza MB izoenzim (CKMB), N-terminalni pro B-tip natriuretski peptid (NT-proBNP), C-reaktivni protein (CRP), Laktat dehidrogenaza (LDH), Mokraćna kiselina (Acidum uricum). Ciljevi ovog rada su bili da se kreira model za predviđanje preoperativnog rizika kardiohirur&scaron;kih bolesnika sa oslabljenom sistolnom funkcijom leve komore na osnovu preoperativnih vrednosti određenih biomarkera i da se kreira novi model sa kombinacijom prethodnog modela i već postojećeg modela EuroSCORE II. Ispitana su 704 bolesnika sa oslabljenom sistolnom funkcijom leve komore, ejekcione frakcije manje ili jednake 50%. Bolesnici su operisani na Institutu za kardiovaskularne bolesti Vojvodine, od 20. januara 2014. do 20. aprila 2016. Kod bolesnika su urađene tri vrste operacija: revaskularizacija miokarda-koronarna hirurgija, hirurgija stečenih srčanih mana - valvularna hirurgija i kombinovane operacije. Od biohemijskih analiza, 24 sata pre operacije, urađene su sledeće analize: troponin I, kreatin kinaza, kreatin kinaza MB izoenzim, masena kreatin kinaza, laktat dehidrogenaza, C-reaktivni protein, NT-proBNP i mokraćna kiselina. Praćen je postoperativni mortalitet, postoperativni infarkt miokarda i postoperativni cerebrovaskularni incident i njihova povezanost sa preoperativnim vrednostima nabrojanih biomarkera. U studiju su bili uključeni svi bolesnici sa stečenim bolestima srca, stariji od 18 godina, kod kojih je ejekciona frakcija leve komore bila manja ili jednaka 50% i kod kojih su izvr&scaron;ene sledeće vrste operacija: revaskularizacija miokarda - koronarna hirurgija, hirurgija stečenih srčanih mana - valvularna hirurgija i kombinovane operacije - koronarna i valvularna hirurgija. Rezultati su pokazali da je postoperativni mortalitet bio 3,13%, da je postoperativni infarkt miokarda imalo 7,95% a postoperativni cerebrovaskularni incident 9,23% od ukupnog broja ispitanika. 1. Povezanost vrednosti biomarkera sa postoperativnim infarktom miokarda kod bolesnika sa oslabljenom ejekcionom frakcijom leve komore: povi&scaron;ene preoperativne vrednosti troponina I su bile povezane sa postoperativnim infarktom miokarda. Povezanost preoperativnih vrednosti biomarkera sa postoperativnim cerebrovaskularnim incidentom kod bolesnika sa oslabljenom ejekcionom frakcijom leve komore: povi&scaron;ene preoperativne vrednosti troponina I i CRP-a su bile povezane sa postoperativnim cerebrovaskularnim incidentom. 2. Analiziran je uticaj preoperativnog nivoa svih biomarkera, pojedinačno, na značajne neželjene kardijalne i cerebrovaskularne događaje - Major Adverse Cardiac and Cerebrovascular Events (MACCE) kao ishod posle operacije na srcu, kod bolesnika sa oslabljenom ejekcionom frakcijom leve komore. Dobijeni su sledeći rezultati: Preoperativna vrednost nivoa troponina I veća od 0,01&mu;g/L i MACCE bili su povezani. Povećane preoperativne vrednosti nivoa C-reaktivnog proteina (CRP) i postoperativni MACCE bili su povezani. Povećane preoperativne vrednosti nivoa laktat dehidrogenaze (LDH) i MACCE bili su povezani. Zaključci ove teze su: 1. Nezavisni prediktor postoperativnog infarkta miokarda i značajnih neželjenih kardijalnih i cerebrovaskularnih događaja, kod kardiohirur&scaron;kih bolesnika sa oslabljenom sistolnom funkcijom leve komore, ejekcionom frakcijom manjom ili jednakom 50%, jeste povi&scaron;ena preoperativna vrednost troponina I. 2.Vrednost preoperativnog troponina I je slab marker za predviđanje postoperativnog infarkta miokarda i značajnih neželjenih kardijalnih i cerebrovaskularnih događaja, kod kardiohirur&scaron;kih bolesnika sa oslabljenom sistolnom funkcijom leve komore, ejekcionom frakcijom manjom ili jednakom 50%. 3. Na pojavu postoperativnog cerebrovaskularnog incidenta, kod kardiohirur&scaron;kih bolesnika sa oslabljenom sistolnom funkcijom leve komore, ejekcionom frakcijom manjom ili jednakom 50%, ne utiče nijedna od ispitivanih varijabli. 4. Nezavisni prediktori postoperativnog mortaliteta kod kardiohirur&scaron;kih bolesnika sa oslabljenom sistolnom funkcijom leve komore, ejekcionom frakcijom manjom ili jednakom 50%, na osnovu kojih je moguće kreirati prediktivni Model su godine starosti i povi&scaron;ene preoperativne vrednosti NT-proBNP. 5. Kreirani Model je dobar marker za predikciju ishoda posle operacije na srcu, kod kardiohirur&scaron;kih bolesnika sa oslabljenom sistolnom funkcijom leve komore, ejekcionom frakcijom manjom ili jednakom 50%. 6. Povi&scaron;ena preoperativna vrednost NT- proBNP može da bude dobar marker u predikciji smrtnog ishoda posle operacije na srcu kod bolesnika sa oslabljenom sistolnom funkcijom leve komore, ejekcionom frakcijom manjom ili jednakom 50%. 7. Model EuroSCORE II se pokazao kao slabiji marker za predikciju ishoda posle operacije na srcu kod kardiohirur&scaron;kih bolesnika sa oslabljenom sistolnom funkcijom leve komore, ejekcionom frakcijom manjom ili jednakom 50%. 8. Testiranjem kreiranog modela, podelom na manje rizične i vi&scaron;e rizične bolesnike, u odnosu na visinu ejekcione frakcije leve komore, pokazalo se da je model dobar marker za predviđanje smrtnog ishoda posle operacije na srcu, u obe grupe.</p> / <p>Cardiac surgery operative risk assessment in patients with imapired systolic left ventricular function using cardial biomarkers Evaluation of results in cardiac surgery involves monitoring the outcomes of operative treatment in a given time period. Typically, this interval includes 30 days from the date of operation. The most common criteria used for monitoring are the rate of mortality and morbidity, length of stay in the intensive care unit, the total length of hospitalization and medical costs. Risk stratification means that patients can be divided into groups depending on the number and importance of preoperatively identified risk factors, and that the outcome of surgery for each of the patients can be predicted preoperatively. In Europe, in the period of 1995-1999 on the basis of a multi-center study in 8 European countries and 128 cardiac centers in which 19,030 adult patients were operated on, EuroSCORE (European System for Cardiac Operative Risk Evaluation) model for risk stratification in cardiac surgery was developed. However, the inevitable changes and progress in the surgical treatment rendered the EuroSCORE model obsolete warranting updated system. It was in 2012 when a new system EuroSCORE II was introduced into practice At the Clinic for Cardiac Surgery of the Institute of Cardiovascular Diseases, EuroSCORE model was introduced in routine clinical use since the beginning of 2001. By analyzing the results, two years after application, it was shown that the model was accurate, and that there was no significant difference between the expected (3.7%) and the actual mortality (3.47%) In recent years, in patients who are candidates for cardiac surgery, more attention is paid to cardiac biomarkers in terms of evaluating their predictive power. The most significant biomarkers in cardiovascular medicine are: Troponin, creatine kinase MB isoenzyme (CKMB), N-terminal pro B-type natriuretic peptide (NT-proBNP), C-reactive protein (CRP), Lactate dehydrogenase (LDH), and uric acid (Uric uricum). The objectives of this study were to create a model to predict preoperative risk for cardiac surgery patients with impaired systolic left ventricular function on the basis of preoperative levels of certain biomarkers and to create a new model with a combination of the previous model and already existing EuroSCORE II model. The study included 704 patients with impaired systolic left ventricular function, ejection fraction less than or equal to 50%. All patients underwent cardiac surgery at the Institute of Cardiovascular Diseases, from January 20th 2014 until 20th April 2016. Patients were submitted to three types of operations: revascularization - coronary surgery, surgery of acquired heart defects - valvular surgery and combined operations. Following biochemical analyses were performed 24 hours prior to surgery: troponin I, creatine kinase, creatine kinase MB isoenzyme, mass creatine kinase, lactate dehydrogenase, C-reactive protein, NT-proBNP and uric acid. Postoperative mortality, postoperative onset of myocardial infarction and occurence of cerebrovascular accident and their correlation with preoperative values of listed biomarkers were registered. The study included all patients with acquired heart disease, older than 18 years, with the left ventricular ejection fraction less than or equal to 50% who were submitted to the following types of operations: revascularization - coronary surgery, surgery of acquired heart diseases - valvular surgery and combined operations - coronary and valvular surgery. The results showed that the postoperative mortality was 3.13%, new onset of postoperative myocardial infarction was detected in 7.95% of the patients and postoperative cerebrovascular accident developed in 9.23% of patients. Correlation of preoperative biomarkers values with postoperative myocardial infarction in patients with impaired left ventricular ejection fraction - elevated preoperative troponin I were associated with postoperative myocardial infarction. Correlation of preoperative biomarkers values with postoperative cerebrovascular incident occurence in patients with impaired left ventricular ejection fraction - elevated preoperative troponin I and CRP were associated with postoperative cerebrovascular incident. The influence of preoperative levels of all biomarkers, separetly, on the rate of significant adverse cardiac and cerebrovascular events - Major Adverse Cardiac and Cerebrovascular Events (MACCE) as the heart surgery outcome, in patients with impaired left ventricular ejection fraction. The following results were obtained: Increased preoperative levels of C-reactive protein (CRP) and postoperative MACCE were related. Increased preoperative levels of lactate dehydrogenase (LDH) and MACCE were related. The conclusions of this thesis are: 1. Independent predictor of postoperative myocardial infarction onset and significant adverse cardiac and cerebrovascular events in cardiac surgery patients with impaired systolic left ventricular function (ejection fraction less than or equal to 50%) is elevated preoperative value of troponin I. 2. Preoperative Troponin I value was poor marker for predicting postoperative myocardial infarction and significant adverse cardiac and cerebrovascular events in cardiac surgery patients with impaired systolic left ventricular function (ejection fraction less than or equal to 50%). 3. None of the studied variables showed influence on the postoperative cerebrovascular accident occurence, in cardiac surgery patients with impaired systolic left ventricular function (ejection fraction less than or equal to 50%). 4. Independent predictors of postoperative mortality in cardiac surgery patients with impaired systolic left ventricular function (ejection fraction less than or equal to 50%), that could be used to create a predictive model are: age and elevated preoperative value of NT-proBNP. 5. Developed model showed satisfactory results for predicting outcome after heart surgery in cardiac surgery patients with impaired systolic left ventricular function (ejection fraction less than or equal to 50%). 6. Elevated preoperative value of NT-proBNP may be a good marker for mortality prediction after the cardiac surgery in patients with impaired systolic left ventricular function (ejection fraction less than or equal to 50%). 7. EuroSCORE II model showed poor performance when predicting outcomes after cardiac surgery in patients with impaired systolic left ventricular function (ejection fraction less than or equal to 50%). 8. Validation of the newly-created model, considering low and medium risk patients, based on the value of left ventricular ejection fraction, showed that the model is a good marker for the mortality prediction in both groups.</p>

Para avaliar as características clínicas e evolutivas em pacientes com formas cardíacas iniciais assintomáticas da doença de Chagas, realizou-se estudo prospectivo em 108 pacientes com idade entre 18 e 50 anos, atendidos entre abril e novembro de 2002 no ambulatório de doença de Chagas da Universidade Estadual de Londrina. Os pacientes foram submetidos a 1)avaliação clínica, 2)eletrocardiograma (ECG), 3)radiografia de tórax e cálculo do índice cardio-torácico (ICT), 4)eletrocardiografia dinâmica de 24 horas, 5)ecocardiografia bidimensional com Doppler tecidual e 6)dosagem plasmática do peptídeo natriurético tipo B (BNP). Os pacientes foram divididos em 3 grupos: 50 no GI - ECG e ICT normais, 31 no GIIA - ECG com alterações características de doença de Chagas e 25 no GIIB - ECG com alterações não características de doença de Chagas / To evaluate clinical and evolutive features in patients with initial asymptomatic cardiac Chagas' disease, a prospective study was carried out with 108 patients, age 18 and 50, at the Londrina State University Chagas' disease outpatient clinic, from April to November 2002. Patients were submitted to: 1) clinical evaluation, 2) electrocardiography (EKG), 3) chest radiography and cardiothoracic index (CTI), 4)24-hour dynamic electrocardiography, 5) bi-dimensional echocardiography with tissued Doppler imaging and 6) type-B natriuretic peptide (BNP) plasmatic dosage. Patients were divided into 3 groups: GI - normal EKG and CTI (50 patients), GIIA - EKG with typical Chagas' disease alterations (31 patients) and GIIB - EKG with alterations not characteristic of Chagas´ disease (25 patients)

Abstract Melatonin is an important modulator of several physiological and behavioural processes, and it influences the function of many different tissues. Melatonin has effective antioxidative properties, but some of its actions in mammals are also mediated through the MT1 and MT2 melatonin receptors. Antioxidative properties are seen especially when the melatonin concentration is high (≥ nM), and melatonin's affinity for its receptors appears at lower concentrations (pM). Recently, the involvement of melatonin in protecting the heart against cardiac diseases, including myocardial infarction (MI), has been brought out. MI alters the structure and function of myocardium, attenuating for example cardiac contractility by affecting the amount and function of the essential Ca2+ handling proteins, dihydropyridine receptor (DHPR), ryanodine receptor (RyR2) and sarco-endoplasmic reticulum (SR) Ca2+-ATPase2 (SERCA2). MI also evokes many adaptive responses in organisms, such as elevated production of atrial and brain natriuretic peptides (ANP and BNP). In this thesis, the expression of MT1 and MT2 receptor mRNAs was investigated in several rat tissues. Furthermore, the effect of MI and exogenous melatonin on the rat endogenous melatonin and on the expression of cardiac MT1, MT2, DHPR, RyR2 and SERCA2 proteins was evaluated. The concentrations of ANP and BNP were also measured after post-MI melatonin administration. The results show the expression of MT1 and/or MT2 receptor mRNAs in the hypothalamus, retina, small intestine, liver and heart, which indicates that at least some effects of melatonin could be mediated through the receptors in these tissues. Melatonin synthesis in the pineal gland increased rapidly in response to MI, supporting an important role of endogenous melatonin in protecting the heart after MI. Furthermore, exogenous melatonin altered the mRNA expression of DHPR, RyR2 and SERCA2 after MI, suggesting that melatonin might contribute to the post-infarction cardiac contractile function. The results also revealed a novel, positive relationship between melatonin and ANP, and thereby bring out one more possible way of melatonin to protect the heart against MI-induced injuries. Taken together, the present thesis (i) supports the notion that melatonin is an important endogenous protective agent of the organism, and (ii) extends our knowledge of melatonin's post-infarction cardioprotective actions. / Tiivistelmä Melatoniini osallistuu monien fysiologisten toimintojen ja käyttäytymisen säätelyyn sekä vaikuttaa useiden eri kudosten toimintaan. Melatoniini on tehokas antioksidantti, mutta jotkut sen vaikutuksista välittyvät myös MT1 ja MT2 melatoniini reseptorien kautta. Antioksidatiiviset vaikutukset tulevat esiin erityisesti silloin, kun melatoniinin pitoisuus on korkea (≥ nM). Alhaisemmilla pitoisuuksilla (pM) on puolestaan havaittavissa melatoniinin sitoutuminen reseptoreihinsa. Viime aikoina on tullut esille melatoniinin mahdollinen suojavaikutus sydänsairauksia, kuten sydäninfarkteja, vastaan. Sydäninfarkti muuttaa sydänlihaksen rakennetta ja toimintaa esimerkiksi vaikuttamalla supistuksen kannalta välttämättömien proteiinien, dihydropyridiini reseptorin (DHPR), ryanodiini reseptorin (RyR2) ja sarko-endoplasmakalvoston Ca2+-ATPaasi2:n (SERCA2) lukumääriin ja toimintaan, ja sitä kautta muun muassa heikentää sydämen supistuvuutta. Sydäninfarkti laukaisee elimistössä myös monia adaptiivisia vasteita, kuten eteispeptidin (ANP) ja aivojen natriureettisen peptidin (BNP) lisääntyneen erityksen. Tässä väitöstyössä tutkittiin MT1 ja MT2 reseptorien mRNAn ilmentymistä useissa rotan eri kudoksissa. Lisäksi tutkittiin sydäninfarktin ja eksogeenisen melatoniinin vaikutuksia rotan endogeeniseen melatoniiniin sekä sydämen MT1, MT2, DHPR, RyR2 ja SERCA2 proteiinien ekspressioon. Myös ANP ja BNP pitoisuudet mitattiin. Tulokset osoittivat MT1 ja/tai MT2 reseptori mRNAn ilmentymisen hypotalamuksessa, silmän verkkokalvolla, ohutsuolessa, maksassa ja sydämessä, minkä perusteella ainakin osa melatoniinin vaikutuksista saattaisi olla reseptorivälitteisiä näissä kudoksissa. Tulosten mukaan käpyrauhasen melatoniinisynteesi lisääntyi nopeasti sydäninfarktin jälkeen, mikä tukee käsitystä endogeenisen melatoniinin tärkeästä roolista infarktin jälkeisessä sydämen suojauksessa. Lisäksi eksogeeninen melatoniini muutti DHPR:n, RyR2:n ja SERCA2:n mRNA ekspressiota infarktin jälkeen, mikä voisi merkitä, että melatoniini saattaa vaikuttaa infarktin jälkeiseen sydämen supistuvuuteen. Tulosten osoittama positiivinen riippuvuus melatoniinin ja ANP:n välillä tuo puolestaan esille yhden uuden mahdollisen keinon, jonka kautta melatoniini voisi suojata sydäntä infarktin aiheuttamia vaurioita vastaan. Yhteenvetona voidaan todeta, että tämä väitöstyö (i) tukee käsitystä, että endogeenisella melatoniinilla on tärkeä merkitys elimistön suojaamisessa, ja (ii) laajentaa tietämystämme infarktin jälkeisistä melatoniinin sydäntä suojaavista vaikutuksista.