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Metabolites of arachidonic acid, known as eicosanoids, result from two enzymatic pathways: cyclooxygenase (COX) and lipoxygenase (LOX). Indomethacin (INDO), at a dose level of approximately 10 mg/kg, has been commonly used in studies on the role of prostagiandins (PG) in the porcine ovulatory process since it was believed to be specific in its inhibition of the COX pathway. Other evidence suggests that INDO also has inhibitory effects on the formation of LOX metabolites including 12- and 15-hydroxyeicosatetraenoic acid (HETE). There is also evidence that LOX metabolites may have a role in the ovulatory process of the rat and the pig. In the previous studies on PGs in porcine ovulation, the effect of INDO on LOX metabolites was not examined. It has been shown that progesterone has a role in the formation of eicosanoids in the ovary in the rat and the ewe. The results of this study indicate that an intramuscular injection of INDO, at dose levels as high as 5 mg/kg, reduces ovulation rat and preovulatory follicular fluid concentrations of PGF2alpha without affecting concentrations of 12- and 15-HETE in the gonadotropin-primed pig. Indomethacin, at dose levels as low as 1 mg/kg, reduced ovulation rate and intrafollicular PGF2alpha concentrations but 0.1 mg/kg had no effect on ovulation rate or PGF2alpha. In cultured granulosa and theca interna cells, 10 ng or greater of INDO per 3 x 105 cells reduces PGF2alpha accumulation in the media. Accumulation of 12- and 15-BETE in the media was reduced by 100 ng or greater of INDO per 3 x 10 5 cells. To examine the role of progesterone in the formation of eicosanoids, danazol, an inhibitor of steroidogenesis, was added to cultures of porcine follicular cells. This treatment had no effect on progesterone production by either cell type and, similarly, had no effect on eicosanoid production. (Abstract shortened by UMI.)

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 65-78). / xi, 91 leaves, bound ill. ( some col.) 29 cm

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Graduation date: 2003

Graduation date: 1994

Graduation date: 1993

Sexual maturation and sex differentiation comprise facets of a common theme: reproduction. The endocrine system regulates many of the critical physiological processes necessary for reproduction and offers a framework within which technologies can be developed for controlling sexual maturation and sex differentiation. The studies described in this thesis were undertaken to improve the understanding of the endocrine control of these critical stages of development in salmonids. Final ovarian maturation in salmon is accompanied by dynamic changes in plasma hormone levels. Ovulation can be accelerated through the use of hormones such as gonadotropin releasing hormone or its analogs (GnRHa). The effectiveness of GnRHa often depends on the timing of treatment. To determine if plasma concentrations of steroids can be used to predict the sensitivity of adult female coho salmon (Oncorhynchus kisutch) to GnRHa, circulating levels of testosterone, 17α,20β-dihydroxyprogesterone (DHP), and estradiol were measured before and after injection with GnRHa to accelerate ovulation. We found that high levels of testosterone were predictive of early response of coho salmon to GnRHa treatment. The correlation between testosterone and ovulatory response to GnRHa suggested a possible functional relation. However. implantation or injection of testosterone. 17α-methyltestosterone (MT), or the antiandrogen, cyproterone acetate (CA), before or with GnRHa treatment did not affect the ovulatory response of coho or chinook salmon ( 0. tshawytscha) to GnRHa. Chinook salmon treated with MT alone had accelerated ovulation in comparison to controls. If steroids are involved in sex differentiation. steroids must be produced early in development. In vitro production of steroids in both coho salmon and rainbow trout (0. mykiss) was assessed from hatch through sex differentiation. Cortisol, androstenedione, testosterone, and estradiol were produced just after hatching by tissue explants that contained anterior kidneys and gonads of coho salmon. To circumvent the problem of not knowing the sex of individuals until after sex differentiation, single-sex populations of rainbow trout were produced by gynogenesis or androgenesis. Tissue explants produced more androstenedione than testosterone or estradiol. More androgens were produced by testes and more estradiol was produced by ovaries within 6 to 10 weeks of hatching. Dietary treatment with estradiol or MT inhibited gonadal steroid secretion. Electrophoresis of gonadal homogenates from salmonids revealed several sex-specific bands. In particular, a prominent band of about 50,000 daltons was apparent in ovaries but not testes. Production of sex-specific proteins may be affected by dietary steroid treatment. / Graduation date: 1991