Studies on the testicular source of inhibin and its route of secretion in rams: failure of the Leydig cell to secrete inhibin in response to a human chorionic gonadotrophin/LH stimulus.
To determine whether Leydig cells produce inhibin in the ram, Leydig cells were stimulated by administering human chorionic gonadotrophin (hCG) or raising the levels of endogenous LH by an injection of gonadotrophin releasing hormone (GnRH). Plasma concentrations of testosterone increased in the 72 h after either a single injection (P less than 0.05) or two injections (P less than 0.01) of hCG. Plasma concentrations of inhibin were not significantly influenced by either one or two injections of hCG. Administration of GnRH (1 microgram) caused an 11-fold increase in plasma concentrations of LH but did not influence concentrations of inhibin in either the jugular or testicular veins (pampiniform plexus). In contrast, concentrations of testosterone were increased by about fourfold in both jugular (P less than 0.01) and testicular (P less than 0.05) veins. The concentrations of inhibin in the testicular vein were 1.3-fold higher than in the peripheral plasma (P less than 0.05) both before and following treatment with GnRH whereas the concentrations of testosterone were 18- to 21-fold greater than in peripheral concentrations. In view of the difference in concentrations of inhibin between testicular and jugular veins, in a further experiment a sample was taken from the jugular vein, a vein located in the tunica vasculosa of the testis (testicular vein) and from a vein (spermatic vein) and lymph vessels located in the spermatic cord. The mean (+/- S.E.M.) concentrations of inhibin were highest in the testicular lymph (45.93 +/- 4.21 micrograms/l; P less than 0.001) compared with the peripheral (4.14 +/- 0.31 micrograms/l), spermatic (8.0 +/- 1.17 micrograms/l) or testicular (6.4 +/- 0.82 micrograms/l) plasma.(ABSTRACT TRUNCATED AT 250 WORDS)
Tilbrook
A J
AJ
Victorian Institute of Animal Science, Department of Agriculture, Werribee, Victoria, Australia.
de Kretser
D M
DM
Clarke
I J
IJ
D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D006801:Humans; D007265:Inhibins / Q000097:blood / Q000378:metabolism*; D007985:Leydig Cells / Q000187:drug effects / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000097:blood / Q000494:pharmacology*; D008297:Male; D012756:Sheep / Q000378:metabolism*; D013737:Testis / Q000378:metabolism*; D013739:Testosterone / Q000097:blood
D006063:Chorionic Gonadotropin; D013739:Testosterone; D007265:Inhibins; D007986:Luteinizing Hormone