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The aim of this study was to clarify the possible involvement of nitric oxide (NO) on prostaglandin (PG) E2-9-ketoreductase activity in the gonadotropin-releasing hormone (GnRH)-dependent PGF2 alpha synthesis by the interrenal gland of the female water frog, Rana esculenta, during the post-reproduction. Interrenal glands were incubated in vitro with GnRH, NO donor (sodium nitroprusside, SNP), and inhibitors of phospholipase C (compound 48/80), inositol triphosphate (decavanadate), calmodulin (calmidazolium), NO synthase (L-NAME), and PGE2-9-ketoreductase (palmitic acid). Production of PGE2 and PGF2 alpha and NO synthase and PGE2-9-ketoreductase activities were determined. GnRH and SNP increased PGF2 alpha production and PGE2-9-ketoreductase activity, and decreased production of PGE2 and GnRH increased NO synthase activity. GnRH effects were blocked by all inhibitors, except for palmitic acid, which did not affect NO synthase activity, which is increased by GnRH. This study indicates that NO may be involved in regulation of the R. esculenta post-reproduction through stimulation of PGE2-9-ketoreductase activity in GnRH-dependent PGF2 alpha synthesis by the frog interrenal gland.

The in vitro effects of prostaglandin F2 alpha (PGF2 alpha) and prostaglandin E2 (PGE2) on corticosterone release by ovarian follicles, corpora lutea (CL), and interrenals were studied in the female lizard, Podarcis sicula sicula, during reproduction. Follicles and CL studied in the female lizard, Podarcis sicula sicula, during reproduction. Follicles and CL were divided according to their different developmental stages; follicles: previtellogenic, early-vitellogenic, mid-vitellogenic and fully-grown; CL: CL1 (unshelled eggs in the oviducts), CL2 (shelled eggs in the oviducts), CL3 (eggs laid 6 h previously) and CL4 (eggs laid 48 h previously). Interrenals were divided according to the reproductive stages: pre-vitellogenesis, vitellogenesis, ovulation, post-ovulation, and post-deposition. PGF2 alpha release was highest in fully-grown follicles and PGE2 in early-vitellogenic follicles, corticosterone was highest in pre-vitellogenic and lowest in early-vitellogenic follicles. PGE2 decreased corticosterone in pre-vitellogenic, mid-vitellogenic and fully-grown follicles. PGF2 alpha release was highest in CL4, and PGE2 in CL1 and CL2, corticosterone was highest in CL4. PGF2 alpha increased corticosterone in CL1, CL2 and CL3. In interrenals, PGF2 alpha release was highest and PGE2 lowest during ovulation, corticosterone was highest during ovulation. PGF2 alpha increased and PGE2 decreased interrenal corticosterone during vitellogenesis, ovulation, and post-ovulation. In the plasma, PGF2 alpha levels were highest and PGE2 lowest during ovulation, corticosterone was highest during ovulation. These results suggest that corticosterone, modulated by PGF2 alpha and PGE2, is implied in the reproductive processes with different roles. In fact this steroid could favour ovulatory and luteolytic processes. In addition the hypothesis of an anti-vitellogenic role of corticosterone is discussed.

The present study was carried out to evaluate the in vitro brain release of prostaglandin F 2 α ( PGF 2 α ), prostaglandin E 2 (PGE 2 ), androgens, and 17 β -estradiol in male and female crested newt, Triturus carnifex, during three different periods of the annual sexual cycle; in addition, the effects of mammalian gonadotropin-releasing hormone (mGnRH), PGF 2 α , and PGE 2 on prostaglandins and steroids release by the brain were evaluated during the same periods. In brain incubations of both sexes, PGF 2 α and estradiol were higher during postreproduction, while PGE 2 and androgens were higher during reproduction. In both sexes, mGnRH increased PGF 2 α and estradiol during postreproduction, and PGE 2 during reproduction; PGF 2 α increased estradiol secretion during postreproduction. Only in the male, did both mGnRH and PGE 2 increase androgens during reproduction. It could be suggested that in Triturus carnifex , the regulation of the reproductive activity in the central nervous system (CNS) depends on the relationships among mGnRH, prostaglandins and steroids. In particular, PGF 2 α and PGE 2 seem to play different roles in the CNS of the newt: PGF 2 α is involved in the postreproductive processes, through estradiol secretion, while PGE 2 in the reproductive ones (through androgens secretion?).

Plasma prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha), androgens and estradiol-17 beta were measured in the male water frog, Rana esculenta, during the annual sexual cycle. In vivo experiments were carried out to study the effects of PGE2 and PGF2 alpha on plasma sex steroids during the following periods: prereproduction (April), reproduction (May), postreproduction (June) and recovery (October). In the same months, in vitro experiments were performed to evaluate the effects of these two prostaglandins (PGs) on testicular release of sex steroids. The PGE2 plasma levels peaked in April. PGE2 treatment in vivo increased androgens in April and October, while PGF2 alpha increased estradiol-17 beta in June and October. In in vitro experiments, PGE2 increased androgens in April, while PGF2 alpha increased estradiol-17 beta in October. These results suggest that PGE2 could induce the breeding activity, probably through androgens synthesis. PGF2 alpha could interrupt the breeding, through estradiol-17 beta secretion.

In Rana esculenta a correlation has been established between the oviducal RNA content and oviduct weight changes during the annual cycle. Hypophysectomy and ovariectomy reduce the RNA content but this can be increased with suitable replacement therapy. The data support the view that RNA is implicated in the regulation of the oviducal gland activity.

1. 1. The steroid content of the ovaries and fat bodies of female Triturus cristatus carnifex have been analysed during the breeding season. 2. 2. Progesterone and androstenedione have been identified in the ovarian extract; the following steroids have been identified in the fat bodies: pregnenolone, progesterone, dehydroepiandrosterone, testosterone and estrone. 3. 3. Incubations of acetone powder carried out separately with ovarian and fat body tissue using cholesterol-4-C14 as the substrate yielded the following metabolites in the case of the ovary: progesterone, 17α-hydroxyprogesterone, androstenedione, testosterone; and in the case of the fat bodies: pregnenolone, 17α-hydroxypregnenolone, 17α-hydroxprogesterone, and testosterone. 4. 4. Incubations with either tissue using testosterone-4-C14 as the substrate yielded 11-ketotestosterone, 11β-hydroxyandrostenedione, androstenedione and esterone. 5. 5. These findings support the view that steroid hormones identified in the fat bodies could be produced in situ from cholesterol.

1. 1. The metabolism of pregnenolone-7α- 3 H and progesterone-4- 14 C was studied in the ovary and fat bodies of Triturus cristatus carnifex . The effect of ovariectomy and fat bodies asportation was examined. 2. 2. From the values of the ratio 3 H/ 14 C for testosterone it appears that in the ovary the biosynthetic pathway may go through pregnenolone → 17 α-hydroxypregnenolone → dehydroepiandrosterone , while in the fat bodies the preferential pathway is pregnenolone → progesterone → 17 α-hydroxyprogesterone . 3. 3. The amounts of 17 α-hydroxypregnenolone formed by the ovary are much higher than those synthesized by fat bodies. 4. 4. The ovary of fat-body-deprived animals show a different trend with time of 17 α-hydroxypregnenolone and dehydroepiandrosterone formation, while ovariectomy causes a decrease of dehydroepiandrosterone in the fat bodies.

The plasmatic profiles of androgens, estradiol, and progesterone, together with gonads and SSC modifications, have been followed, throughout the post-reproductive period in two Rana esculenta populations, inhabiting, respectively, a mountain pond (Colfiorito) and a sea level lagoon (Lesina). Testosterone and progesterone progressively decrease in the blood until July, while estradiol shows, in both sexes, an increase in the same month. Testosterone depletion accounts for thumb pad atrophy in the male and probably, in both sexes, for the summer interruption of sexual behavior. The estradiol increase could be linked to the induction of vitellogenin synthesis by the liver or, alternatively, could act through negative feed-back on the brain centers involved in GnRF synthesis and therefore it could be responsible for an inhibition of LH release and, in turn, of androgen synthesis/secretion by the gonads. The last function can be framed in the endocrine regulation of the so-called "refractory period" which interrupts the breeding during the summer. The hematic level of progesterone is higher during the ovulation period and this is consistent with the role assigned to the hormone, i.e., the induction of jelly release from oviductal glands. The hormonal trends in the blood of the two frog populations are very similar, although some differences exist in the levels of testosterone and progesterone.

Mammalian gonadotropins and partially purified gonadotropins (FSH and LH) from an amphibian (Rana esculenta) were used to investigate their action on enzymatic activity of delta 5-3 beta-HSD in male and female hypophysectomized Rana esculenta in stage of genital activity (October) and in stasis or hibernation stage (January). Amphibian and equine LH stimulate delta 5-3 beta-HSD activity especially in females hypophysectomized in the stage of genital activity, while ovine FSH action is very low and amphybian FSH practically inactive. The present data suggested that control of gonadotropic activity in the reproductive cycle in Rana esculenta is LH-dependent.

In hypophysectomized females, Rana esculenta, a significant uptake of labeled ovine FSH and LH was evident in both the ovary and oviduct. This binding was specific only for the ovary. Ovariectomy did not modify the affinity of the oviduct for these gonadotropins. The possibility of the presence of discrete receptor molecules for FSH and LH in the ovary of Rana esculenta is discussed.

The estrogen content of the plasma of females of Rana esculenta has been analyzed during the annual cycle, and following ovariectomy. Estriol has been detected during the hibernation period (from December to April), while estradiol-17β was present only in January. The plasma of the ovariectomized animals did not show any detectable amount of estrogens 4 and 5 months after castration; plasma of the sham-operated females contained only traces of estriol.