Isoelectric focusing of rat pituitary gonadotropins

Isoelectric focusing of rat gonadotropins has been studied using a small scale column and various pH gradients. Hormones were detected by radioimmunoassay. FSH focuses as a single peak, the pI being 2.8. It is thus slightly more acidic than the pI of FSH from other species. LH is more heterogeneous, the main activity focusing in the pH 9.0 area, whereas a second activity appears, for some samples, in the acidic part of the gradient. TSH exhibits a broad zone of activity between pH 7.0 and 10.0. The fractionation of pituitary glycoproteins using a pH 3-10 gradient followed by removal of sucrose and ampholytes through Sephadex G 50 chromatography allows the recovery with good yields of a purified rat FSH fraction devoid of LH activity as estimated by radioimmunoassay.