The Effects of Ovariectomy, Estrogen Replacement, and Neuraminidase Treatment on the Properties of the Adenohypophysial Glycoprotein Hormones of the Rhesus Monkey

Abstract

A comparison of pituitary extracts from intact and ovariectomized monkeys revealed that, like FSH, LH from ovariectomized animals is larger in average apparent molecular size and disappears from the circulation of test rats less rapidly than does LH from intact females. In contrast, ovariectomy had no effect on the apparent molecular size of TSH nor on its disappearance rate following injection into test rats. Reversal of the effect of ovariectomy on the molecular size of both LH and FSH was achieved by the chronic administration of estradiol. The differences in apparent molecular size of gonadotropins from intact and ovariectomized monkeys were either reduced or abolished by digestion with the enzyme neuraminidase. These findings suggest that the qualitative changes in the gonadotropins consequent to ovariectomy represent a specific response to the removal of estrogen and are consonant with the view that this phenomenon involves changes in the sialic acid content of the gonadotropins.