Gonadectomy modifies the gender specific pattern of desensitization of pituitary cells by gonadotropin-releasing hormone in the superfusion system.
The effect of a 6-h infusion of 1 nM gonadotropin-releasing hormone (GnRH) on LH release from dispersed anterior pituitary cells from rats in metoestrus ("metoestrus cells"), intact male rats ("male cells"), ovariectomized rats ("ovx cells"), and from orchidectomized rats ("orchidex cells") was investigated. Using metoestrus cells the initial amplitude of the response was high but desensitization was strong: the amount of LH secreted in the last 90-min period of the 6-h incubation was less than 20% of the initial value. In male cells, the immediate response was weaker; however, in the second 90-min of the 6-h incubation a 20% to 30% increase was observed and even in the fourth 90-min period the amount of LH secreted was more than 70% of the initial levels. Gonadectomy diminished the gender specific differences. Desensitization became less pronounced when ovx cells were used and its level was found to increase in orchidex cells, as compared to metoestrus cells and male cells, respectively. The responses to 3-min pulses of GnRH and KCl given after the 6-h incubation were strongly reduced in metoestrus cells but increased in male cells, compared to the initial peaks. Gonadectomy nullified these differences, too. Our data show that gonadectomy causes alterations in the intracellular pools of LH available for immediate and prolonged release in male and female rats. Decrease of estrogen in the sex steroid balance of female rats reduces the amount of LH available for immediate release and relatively increases the rate of replenishment into the immediate release pool. This allows a more stable secretion of LH during the 6-h stimulation. Decrease in androgens causes opposite changes. These phenomena could be observed in vitro, after keeping the pituitaries in a hormone free milieu for 16-28 h.
Horváth
J E
JE
Department of Human Anatomy, University Medical School, Pécs, Hungary.
Helyes
Z
Z
Flerkó
B
B
D000818:Animals; D004351:Drug Resistance; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D066298:In Vitro Techniques; D007986:Luteinizing Hormone / Q000378:metabolism; D008297:Male; D009919:Orchiectomy; D010052:Ovariectomy; D010053:Ovary / Q000502:physiology*; D010903:Pituitary Gland, Anterior / Q000187:drug effects* / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012727:Sex Characteristics; D013737:Testis / Q000502:physiology*
D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone