EFFECTS OF RECOMBINANT HUMAN INHIBIN AND TESTOSTERONE ON GONADOTROPIN-SECRETION AND SUBUNIT MESSENGER-RNA IN SUPERFUSED MALE-RAT PITUITARY CELL-CULTURES STIMULATED WITH PULSATILE GONADOTROPIN-RELEASING-HORMONE

[摘要] Effects of recombinant human inhibin (rh inhibin) and testosterone on follicle-stimulating hormone (FSH) and luteinizing hormone (LH) secretion and mRNA levels of gonadotropin subunits were investigated in superfused male rat pituitary cell cultures. During superfusion, the cells were stimulated with gonadotropin-releasing hormone (GnRH) pulses (10 nM, 6 min/h) and exposed to rh inhibin (2 ng/ml) and/or testosterone (10 nM) for up to 20 h. The concentrations of FSH and LH were measured in effluent media by radioimmunoassay (RIA), and subunit mRNAs were determined by Northern blot hybridizations using rat FSH-beta, LH-beta and alpha genomic and cDNA probes. Rh inhibin suppressed the secretion of FSH (30-40% of control) and the secretion of LH to 50-60% of control, but inhibited only FSH-beta mRNA (to non-detectable levels). Testosterone alone suppressed the release of LH to 50% of control, whereas FSH release was increased to 130-160% (P < 0.05) of control. This increase was due to higher interpulse values without significant changes in the pulse amplitude. Also FSH-beta mRNA level was increased (1.5-fold, P < 0.05) but only after 17-20 h of treatment. On the other hand, testosterone had no effect on LH-beta and alpha subunit mRNA levels. Testosterone in combination with rh inhibin showed an inhibitory effect on LH-beta mRNA; however, the pattern of LH release was not significantly different from that observed with rh inhibin or testosterone alone. Combined effects of testosterone and rh inhibin on FSH secretion and FSH-beta mRNA were similar to those observed with rh inhibin alone. These results indicate that in presence of pulsatile GnRH: (1) testosterone exerts divergent effects on FSH and LH; it is stimulatory for FSH secretion and FSH-beta mRNA, but inhibitory for LH release without affecting LH-beta mRNA level: (2) the stimulatory effects of testosterone on FSH secretion can be masked by rh inhibin; (3) inhibition of FSH secretion by rh inhibin is correlated with the inhibition of FSH-beta mRNA, whereas inhibition of LH release is not accompanied by changes in LH-beta or alpha subunit mRNA.

[发布日期] 1991-12-01

[关键词] FOLLICLE-STIMULATING HORMONE;LUTEINIZING HORMONE;INHIBIN TESTOSTERONE INTERACTIONS