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The in vitro effects of overnight treatment with testosterone (T) on gonadotropin (GTH)-II secretion from primary cultures of dispersed female goldfish pituitary cells were examined. T (100 nM) did not affect basal GTH-II release, but increased GTH-II responses to initial applications of 0.5-h pulses of sGnRH or cGnRH-II in cells from females at sexually regressed, recrudescing, or mature (prespawning) stages. Pretreatment with 10 nM T was also effective, except in experiments with cells from sexually regressed females. Analysis of GTH-II response profiles to the first GnRH pulse revealed that T increased the size of the initial (first 15 min) and sustained (rest of response) release phases, and the duration of the total response to both GnRHs. These results indicate that direct positive influence of T on GnRH-stimulated GTH-II release is demonstrable in cells from female goldfish at all ovarian maturational stages; in addition, T affects both the initial and the sustained response phases. However, compared to the initial GnRH challenge, responses to a second 0.5-h GnRH pulse were decreased in T-treated but not in control cells, suggesting that T also enhanced desensitization. Ovarian maturational conditions modulated the effects of T on the GTH-II response kinetics. In cells prepared from sexually regressed females, T treatment changed the “monophasic” (initial phase only) GTH-II response to sGnRH to a “biphasic” one characteristic of cells prepared from fish at later stages of gonadal recrudescence. Advancing gonadal maturity increased the magnitude of both initial and sustained phases of the T-enhanced GTH-II response to sGnRH, but only elevated the initial phase of T-potentiated cGnRH-II-induced release. Direct actions of T on pituitary cells may play a role in ovarian steroid feedback regulation of GTH-II secretion during the seasonal reproductive cycle in goldfish.

Gonadal steroid levels were determined in the ovary of Salamandra salamandra infraimmaculata during the reproductive cycle in populations from a xeric region in northern Israel. Varying proportions of previtellogenic and vitellogenic oocytes were present throughout the year, and mature oocytes were present in winter and spring. The numbers of mature oocytes were greater between December and April, after parturition. The levels of 17 beta-estradiol and testosterone rose during oocyte vitellogenesis and maturation. Levels of progesterone and 17 alpha-hydroxy progesterone appeared to be related to the level of vitellogenesis. Gravid females contained greater quantities of all four steroids than did nongravid females.

Mammalian LH (250 μg of NIH-LH-B9) and FSH (500 μg of FSH-P, Armour-Baldwin) elicit increases in serum estradiol (E) and progesterone (P) of laying turkeys within 30 min after a single iv injection. Prolactin (NIH-P-S11) at doses of 250 and 500 μg had no effect on the E or P levels when given in a single iv injection. One thousand micrograms of prolactin caused a significant decrease in serum E within 30 min of injection. Prolactin (500 and 1000 μg), given 30 min before LH, blocked the LH induced rise in P and at doses of 250, 500 and 1000 μg it blocked the LH induced rise in E. Five hundred and 1000 μg of prolactin blocked the FSH induced rise in P and doses of 250, 500 and 1000 μg of prolactin blocked the FSH induced rise in E. It is concluded that prolactin's antigonadotropic effect is exerted, at least in part, by interfering with gonadotropin induced increases in ovarian steroid levels in the blood.