Joyce E. Lehmeyer

Prolactin and growth hormone production as influenced by catecholamines and agents that affect brain catecholamines.

The in vitro influence of dopamine on the in vitro incorporation of leucine-4,5-3H into rat pituitary gland prolactin and growth hormone was studied. This catecholamine primarily inhibited

Effect of Anti-mitotic Drugs on the in Vitro Secretory Activity of Mammotrophs and Somatotrophs and on Their Microtubules

Summary Incubation of anterior pituitary glands of female rats with 10-5 M vincristine or colchicine reduced both synthesis and release of prolactin. Incubation of glands of perphenazine-treated male rats with 10-5 M colchicine or vincristine blocked the perphenazine-induced increase in in vitro prolactin synthesis. At 10-4 M, vincristine inhibited synthesis and release of growth hormone by glands of untreated male rats but could not block the dibutyryl cyclic AMP-induced stimulation of growth hormone release. Incubation of glands of male rats with 10 μg/ml cytochalasin B resulted in decreased growth hormone synthesis. Incubation of glands of female rats with the drug significantly decreased synthesis and release of both prolactin and growth hormone. Concomitant electron microscopic observations indicated that cytoplasmic microtubules are uncommon in the pituitary gland and that they are still present after glands were treated with vincristine and colchicine at doses capable of inhibiting prolactin release. For this reason and because no binding of radioactive colchicine to pituitary glands occurred in vitro, it is suggested that microtubules are not significantly involved in prolactin and growth hormone secretion.

Reciprocal relationship between the in vitro synthesis and secretion of prolactin and growth hormone.

Summary A comparison was made of the amount of radioactive leucine incorporated in vitro into prolactin and growth hormone by rat pituitary glands. It was demonstrated that when the production of prolactin is high, the production of growth hormone is low. The converse of this was also observed. The injection of male rats with estradiol or other agents which significantly increased prolactin production caused a decrease in growth hormone production. It is suggested that the pituitary gland tends to produce a constant amount of prolactin and growth hormone and reciprocal changes are brought about by the production of either hormone through some intracellular control mechanism when the hormonal balance is disturbed through a secondary mechanism. We thank Mr. Ronald C. Pace for his excellent technical assistance.