Evidence that secretion of immunoactive inhibin by seminiferous tubules from the adult rat testis is regulated by specific germ cell types: correlation between in vivo and in vitro studies.
This study has assessed whether depletion of specific germ cell types is able to alter the secretion of immunoactive inhibin by adult Sertoli cells in vivo and in vitro. Pachytene and later spermatocytes were depleted (80-100%) by a single administration of methoxy acetic acid (MAA; 650 mg/kg) to adult rats. At intervals between 1 and 42 days posttreatment, rats were killed, and the blood levels of FSH, LH, and testosterone were determined together with the levels of immunoactive inhibin in plasma and testicular interstitial fluid (IF). At the same time intervals, seminiferous tubules (ST; 5 x 2 cm) were isolated from control and MAA-treated rats and cultured for 24-72 h in the presence or absence of rat FSH, (Bu)2cAMP, or MAA under rigorously optimized conditions. The hormonal changes observed were related to the presence/absence of specific germ cell types, as determined by assessment of testicular morphology in perfusion-fixed testes from similarly treated rats. One to 3 days after MAA treatment, coincident with the depletion of pachytene spermatocytes, blood levels of FSH were increased significantly compared with controls; FSH returned to control levels at 7-14 days (when early spermatids were depleted), but were increased again at 21-35 days (when late spermatids were depleted). In contrast, while the plasma levels of immunoactive inhibin were increased 2-fold 3 days posttreatment, they were comparable to controls at 7-14 days, but were decreased substantially at 21-28 days. The levels of immunoactive inhibin in testicular IF were more than doubled 1 and 3 days posttreatment, but were comparable to control levels at all other times. Blood levels of LH showed a similar pattern of change to FSH, although only at 21-28 days after MAA treatment was there a significant increase, while blood levels of testosterone were comparable at all times in control and MAA-treated rats. To confirm that the changes observed in vivo after MAA treatment were indicative of changes in Sertoli rather than Leydig cell secretion of immonoactive inhibin, its secretion by isolated ST was assessed, and a pattern of change similar to that in plasma was observed. Thus, when cultured for 24 h under basal conditions, ST from rats 1-3 days after MAA treatment showed a 2- to 3-fold increase in secretion of immunoactive inhibin, which returned to control levels at 7-14 days before being reduced substantially at 21-28 days and then recovering to control levels; similar changes were observed for FSH- and (Bu)2cAMP-stimulated secretion of immunoactive inhibin.(ABSTRACT TRUNCATED AT 400 WORDS)
Allenby
G
G
Medical Research Council Reproductive Biology Unit, Centre for Reproductive Biology, Edinburgh, Scotland.
Foster
P M
PM
Sharpe
R M
RM
D000085:Acetates / Q000494:pharmacology; D000818:Animals; D005640:Follicle Stimulating Hormone / Q000097:blood; D007265:Inhibins / Q000097:blood / Q000276:immunology / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D009924:Organ Culture Techniques; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D012671:Seminiferous Tubules / Q000378:metabolism*; D013090:Spermatocytes / Q000187:drug effects / Q000502:physiology; D013094:Spermatozoa / Q000166:cytology / Q000502:physiology*; D013737:Testis / Q000166:cytology / Q000502:physiology*; D013997:Time Factors
D000085:Acetates; D007265:Inhibins; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; C013598:methoxyacetic acid