Isoforms and half-life of FSH from sheep with different reproductive states

The glycoprotein hormone FSH comes in many different isoforms. In humans an d rats the charges of the FSH isoforms vary with reproductive state and the se affect the half-life of FSH in plasma. In this study we examined the cha rge heterogeneity of FSH in pituitary extracts from sheer with different re productive states. Also the half-life of clearance of pituitary FSH from th e different reproductive states was determined in mice. Pituitaries were co llected from: anoestrous, luteal phase, follicular phase, early-pregnant an d late-pregnant ewes, ewe lambs, ram lambs, rams during the breeding and no n-breeding seasons and wethers (5 per group). After extraction, FSH isoform s were fractionated by HPLC anion exchange chromatography. The volume at wh ich half of the FSH had eluted from the ion exchange column was determined (HP50). It was found that FSH isoforms from ewes (HP50 = 96.7 +/- 1.3 ml (S .E.M.)) eluted later (P<0.01) than those from rams (HP50 = 82.3 +/- 1.3 ml) indicating that FSH isoforms in the ewes were more acidic than those from rams. There was a seasonal difference in ewes, with ewes in anoestrus (HP50 = 101.6 +/- 2.6 ml) having more-acidic (P<0.01) FSH isoforms than the ewes during the oestrous cycle (HP50 = 95.3 +/- 0.7 ml). There was an effect of age, with the FSH isoforms from cycling ewes (HP50 = 95.3 +/- 0.7 ml) bein g more acidic (P<0.01) than those from ewe lambs (HP50 = 88.3 +/- 19 ml). T here was an effect of pregnancy, with late-pregnant ewes (HP50 = 107.31 +/- 1.6 ml) having more-acidic FSH isoforms (P<0.05) than those from anoestrou s ewes (HP50 = 101.6 +/- 2.6 ml) and there was an effect of castration with the breeding season rams (HP50 =80.7 +/- 1.4 ml) having more-acidic (P<0.0 5) FSH isoforms than wethers (HP50 = 74.0 +/- 0.5 ml). The half-life of pit uitary FSH from animals in the different reproductive states was found to b e negatively correlated with HP50 (r(2) = 0.56, P<0.01). The FSH isoforms f rom wethers were the least acidic and had the longest half-lives. Collectiv ely, these findings show that in sheep, age, sex and reproductive state are all factors which influence the forms of FSH that are extracted from the p ituitary gland. Moreover, these results demonstrate that FSH from sheep wit h the most-acidic FSH isoforms have the shortest half-life in plasma.