Hypophyseal regulation of hepatic histidase during postnatal development and adulthood: II. Pituitary-estrogen interrelationship

Estrogen, which augments rat liver histidase activity in pre- and postpubertal rats, is ineffective in hypophysectomized animals, in which enzyme activities are already elevated. This failure of estrogen action has been demonstrated in hypophysectomized weanling, as well as adult females, the former of which manifest enzyme activities considerably below maximum possible values. The following agents, which are known to suppress histadase activity under certain conditions, were ineffective in permitting estrogen stimulation of histadase in hypophysectomized rats: glucocorticoid, testosterone, adrenocorticotrophin acting extra-adrenally and via the adrenals, growth, and preparations of whole pituitaries of bovine or female rat origin. The following materials, which do not themselves alter enzymic activity, were likewise incapable of permitting estrogenic enhancement of histadase activity in these animals: follicle-stimulating hormone and luteinizing hormone acting extra-gonadally, thyrotrophic hormone, and bovine posterior pituitary preparations.