Metabolic changes in the rat anterior pituitary and prolactin production following estradiol treatment

The effects of estradiol treatment on the synthesis and release of prolactin and GH in castrated male rats were studied in connection with the anterior pituitary enzymes that represent the hexosemonophosphate shunt, glycolytic, oxidative, and lysosomal activity. LDH and G6P-DH activities increased by 15%–30% at 12 hr and by 70% at 72 hr after estrogen administration. PK activity showed a statistically significant elevation of 20%–40% only after 48–72 hr. ICDH, MDH, acid phosphatase activities, and water-soluble protein concentrations were unchanged. Serum prolactin concentration increased about 400% 24 hr after estradiol injection, and the pituitary synthesized 1000%–1500% more radioactive prolactin in vitro than did control glands. However, no significant increase in prolactin synthesis was observed 12 hr after estradiol treatment.It is suggested that the primary effect of estradiol is on the synthesis of prolactin and that the increased rate of secretion is secondary. Radioimmunoassayable prolactin in the incubated gland tissue and its medium was greatly increased after estradiol treatment. A slight but statistically significant accumulation and decreased release of radioactive GH were also observed. The results suggest a correlation of pituitary prolactin production with the tissue's metabolic activity.