The influence of beta-endorphin on testicular endocrine function in adult rats.
The role of beta-endorphin in testicular steroidogenesis is poorly understood. To address this issue, we treated adult hypophysectomized rats intratesticularly with either saline-50% polyvinylpyrrolidone (SAL-PVP) or human beta-endorphin (0.5 microgram/testis; a total of 1 microgram/rat/day) in SAL-PVP for 3 days. Testicular injections were made under ether anesthesia. On Day 3, rats also received injections (s.c.) of either SAL-PVP or 5 micrograms beta-endorphin in SAL-PVP to minimize the dilution of ether in the testis. One hour later, rats were treated (i.p.) with either saline or ovine LH (25 micrograms/rat). One hour after saline or LH injection, blood was obtained via heart puncture for determination of plasma progesterone (P), androstenedione (A-dione), and testosterone (T) levels. The effects of beta-endorphin (50 ng, equivalent to 13.9 pM; or 250 ng, equivalent to 69.6 pM) on P and androgen secretions in vitro were also examined. Intratesticular injections of beta-endorphin significantly (p less than 0.025) decreased the T response to LH treatment, but failed to affect plasma P and A-dione levels. Response of P to LH treatment was increased (p less than 0.005) in medium containing testicular fragments exposed to 250 ng (69.6 pM) beta-endorphin. However, beta-endorphin attenuated LH effects on A-dione and T production in vitro. These studies demonstrate that beta-endorphin inhibits T secretion, possibly because of its effect on the synthesis of T precursors. Thus, testicular beta-endorphin modulates the endocrine function of the testis in adult rats.
Chandrashekar
V
V
Department of Physiology, Southern Illinois University School of Medicine, Carbondale 62901-6512.
Bartke
A
A
D000728:Androgens / Q000097:blood; D000735:Androstenedione / Q000097:blood; D000818:Animals; D007016:Hypophysectomy; D007267:Injections; D007986:Luteinizing Hormone / Q000008:administration & dosage; D008297:Male; D011374:Progesterone / Q000097:blood; D051381:Rats; D011919:Rats, Inbred Strains; D012965:Sodium Chloride / Q000008:administration & dosage; D013737:Testis / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D013739:Testosterone / Q000097:blood; D013997:Time Factors; D001615:beta-Endorphin / Q000008:administration & dosage / Q000502:physiology*
D000728:Androgens; D013739:Testosterone; D000735:Androstenedione; D012965:Sodium Chloride; D011374:Progesterone; D001615:beta-Endorphin; D007986:Luteinizing Hormone