Pituitary follistatin and activin gene expression, and the testicular regulation of FSH in the adult rhesus monkey (Macaca mulatta)

In rats, FSH beta gene expression and FSH secretion are increased and decre ased, respectively, by pituitary activin and follistatin. Because little in formation is available on the paracrine control of FSH secretion in the pri mate, follistatin and activin/inhibin beta (B) messenger RNA (mRNA) levels were measured in pituitaries of adult male rhesus monkeys 6 weeks alter cas tration or sham surgery (n = 5/group). Follistatin mRNA was determined by q uantitative RT-PCR assay using oligonucleotide primers designed to span exo ns 3-5 of the human follistatin gene. Activin/inhibin beta (B) mRNA levels were measured by ribonuclease protection. Orchidectomy resulted in a 100-fo ld increase in plasma FSH concentrations and a 60-fold rise in those of LH. In castrated monkeys, levels of mRNA encoding FSH beta, LH beta, alpha -su bunit, and GnRH receptor (GnRH-R) were increased 21-, 2.1-, 1.7-, and 1.7-f old, respectively (P < 0.01). Levels of pituitary follistatin and activin/i nhibin beta (B) mRNAs, however, were similar in castrated and intact animal s. These data suggest that the paracrine control of FSH secretion in the ma le differs substantially in primates and rodents. Specifically, the relativ ely greater postcastration rise in FSH beta gene expression and FSH secreti on in the adult male monkey may result because in this species pituitary fo llistatin gene expression does not increase after orchidectomy, as it does in the rat.