Recombinant human activin-A stimulates basal FSH and GnRH-stimulated FSH and LH release in the adult male macaque, Macaca fascicularis

Abstract Activin-A is a homodimer of the BA inhibin subunit that stimulates FSH secretion by pituitary cells in vitro; however, the physiological relevance of this effect is unknown. We have examined whether recombinant human activin-A (activin-A ; 80 μg/kg/day iv infusion for 50.5 h) has in vivo bioactivity in the adult male macaque (n=5). Serum FSH and LH bioactivity and serum testosterone (T) levels were measured on 2 control days and after 24 and48 h of activin-A administration. Basal FSH levels increased significantly (p<0.05) by 17% at 24 h and 82% at 48 h during activin-A administration. No changes in basal LH or T levels were seen. The FSH and LH responses toGnRH (5 Hg/kg, iv bolus) increased significantly (p<0.05) by 117% and 55% after 48 h of activin-A, respectively. A small (16%), but statistically significant (p<0.05), increase in the T response to the GnRH challenge was also noted. These data are preliminary evidence in support of a physiological role for activin-A in the control of gonadotro...