No abstract

Serum LH, FSH and testosterone concentrations were measured by radioimmunoassays in male Sprague-Dawley rats from birth to 80 days of age. The levels of FSH were significantly elevated during the first 5 days of postnatal life. An abrupt decline in FSH concentrations occurred during this period, from levels of 800 ng/ml on day 1 to levels of 300 ng/ml on Day 6. Subsequently, FSH levels fluctuated widely until about Days 30 to 45, when a secondary peak of FSH was observed. Thereafter, a decline in FSH levels to those found in adult rats occurred. This decline in FSH levels appears to coincide with the first release of mature spermatozoa from the germinal epithelium in the testis. During the first 30 days of postnatal life, LH and testosterone values appeared to be inversely related to each other and an LH peak and a nadir of testosterone levels was observed between Days 6 and 14 at time corresponding to regression of the fetal generation of interstitial cells. A parallel rise in LH and testosterone levels occurred from Days 30 to sexual maturity and corresponded to the development of the adult generation of intestitial cells.

No abstract

The response of the pituitary-testicular axis to LH-RH infusion was investigated in rams from birth to sexual maturity. During early postnatal life ram lambs were responsive to LH-RH stimulation and heightened pituitary sensitivity was observed in rams aged 2-3 months. It is suggested that a change in sensitivity of the pituitary\x=req-\ testicular axis occurs at this time and perhaps represents the time of initiation of the pubertal process.

Hybridization histochemistry has been used to detect the presence of mRNA for the \ g=a\and \ g=b\ A subunit of inhibin in tissue sections of the ovary of cows. 32P-labelled cDNAs, complementary to the bovine \g=a\or \ g=b\ A subunit of inhibin or to a control segment of plasmid DNA (pBR 322), were used. The \g=a\subunit mRNA was located in the granulosa layer of antral follicles >0\m=.\36mm in diameter while the \g=a\and \ g=b\ A subunit mRNA were both present in follicles of >0\m=.\8mm. In these latter follicles, the thecal layer hybridized with only the \ g=a\ subunit mRNA. No hybridization of the \ g=a\ or \ g=b\ A subunit probe was found in the cells of the corpus luteum. Hybridization of both probes was abolished when the tissue sections were pretreated with ribonuclease (RNAse). The plasmid cDNA did not hybridize to any of the tissue sections. This study demonstrates that mRNA for the \g=a\inhibin subunit can be detected in granulosa and theca cells whereas the \ g=b\ A inhibin subunit mRNA is restricted to the granulosa cells. These results provide evidence for an independent regulation of expression for the two subunits of inhibin.