Stress-induced testicular hyposensitivity to gonadotropin in rats. Role of the pituitary gland.
The time course of stress-induced testicular hyposensitivity to gonadotropins was studied in hypophysectomized or naloxone-treated rats exposed to various periods of immobilization. Blood was collected from a chronically indwelling intra-atrial catheter every hour for luteinizing hormone (LH) and testosterone (T) measurement. Eight hours of immobilization completely suppressed T secretion without significant effect on LH. Human chorionic gonadotropin (hCG, 5 IU/rat, i.m.) induced a marked increase in plasma T levels in normal control groups 3 h post-injection while in immobilized rats the response was completely abolished, even after only 30 min of stress. In hypophysectomized rats, as expected, plasma T levels were undetectable, but, contrary to results obtained in normal animals, hCG induced a similar increase of plasma T levels both in control and stressed rats. Immobilization stress failed to inhibit plasma T values in hypophysectomized rats pretreated for 4 days with human menopausal gonadotropin (hMG) + hCG, while it did so in similarly treated normal animals. Naloxone induced a rise of plasma LH and T levels in control rats, but did not antagonize the stress-induced fall of plasma T concentration. In all groups, steroid testicular content mimicked variations of plasma T values. In particular, in stressed animals the lack of accumulation of testicular 17-hydroxyprogesterone probably reflected a normal activity of 17-20 lyase. These results indicate that stress induces very rapidly a state of Leydig cell hyposensitivity to gonadotropins and a blockade of T biosynthesis. The causal relationship between the two effects is presently not clear but these events seem to be due to stress-induced release of an inhibitory factor of pituitary origin other that endorphin.
D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D004723:Endorphins / Q000502:physiology; D007016:Hypophysectomy; D007103:Immobilization; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D010902:Pituitary Gland / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013312:Stress, Physiological / Q000503:physiopathology*; D013737:Testis / Q000032:analysis / Q000187:drug effects*; D013739:Testosterone / Q000097:blood
D006063:Chorionic Gonadotropin; D004723:Endorphins; D009270:Naloxone; D013739:Testosterone; D000324:Adrenocorticotropic Hormone