The phenomenon of GnRH-independent secretion of FSH was difficult to explain until the FSH-regulating proteins—inhibins,actinins,£mdfollistatin(FS)—wereidenti-fied. Inhibins and activins are structurally related dimeric glycoproteins, initially isolated from follicular fluids based on their ability to inhibit and stimulate, respectively, the release of FSH. Both inhibins and activins consist of two of three subunits, a and pA or pB, while FS is a single peptide. buy cipro
Markedly greater plasma FSH concentrations and pituitary FSHp mRNA were detected in Meishan (MS) boars than in boars of contemporary U.S. breeds, but no such difference was observed between MS and White Composite (WC) females. Previously we found greater expression of inhibin/activin (I/A) pB in anterior pituitaries of MS than in WC boars, but no differences were observed between these two breeds for the other genes screened. It was unknown whether such a disparity was related to the elevated plasma FSH concentrations in MS boars or whether it was an intrinsic breed difference. In order to address this question, we selected two groups of MS X WC crossbred boars that had either high or low plasma FSH concentrations, and we evaluated expression of FSHp, I/A pB, FS, GnRH-R, and calmodulin genes. Calmodulin was included for evaluation because it was identified by differential display of pituitary cDNA as being different in pi-tuitaries of MS and WC boars (unpublished results). Calmodulin is a regulator of intracellular calcium influx, and the response of pituitary gonadotrophs to GnRH is dependent upon calcium mobilization.