Studies on metabolism and effects of estrogen on pituitary prolactin and LH secretion.

The research article covers estrogen’s role in the secretion of pituitary prolactin and luteinizing hormone (LH) in rats and mares. It focuses on providing understanding about estrogen’s effect on these hormones by administering different dosages of estrogen and evaluating the changes caused by it.

Effects of Estradiol on Pituitary Prolactin Secretion in Rats

• The research describes how estrogen affects the secretion of pituitary prolactin in rats.
• Different doses of estradiol, a type of estrogen, were injected into mature and immature rats. Taking a reference of control, these doses varied from low (0.1 mug/day/rat) to moderate (5 mug/day/rat).
• This hormone dosage led to an increase in pituitary prolactin content and the level of serum prolactin by five to ten times.
• An interesting observation was made when high doses of estrogen were administered. It was less effective in promoting prolactin secretion.
• Furthermore, if progesterone was introduced alongside estrogen, it appeared to somewhat inhibit the stimulatory effects of estradiol on prolactin secretion.

Impact of Serum Estradiol Level on Luteinizing Hormone Secretion

• The research also delves into studying the relationship between serum estradiol level and luteinizing hormone (LH) secretion in mares, with specific focus on dosages and their effects.
• Intramuscular injection of a low dose (2 or 4 mg/mare) of estradiol was found to stimulate LH secretion whereas a high dose (8 mg/mare) inhibited the LH secretion.
• The serum level of estradiol during proestrus, an initial period of the estrous cycle, was found to be critical for facilitating the LH surge leading to ovulation.

Estradiol Metabolism in Mares

• The final part of the research sheds light on the metabolism of estradiol in mares.
• The metabolism studies suggested that estradiol has a relatively long half-life in mares.
• Majority of the estradiol metabolites were detected in the urine within 24 hours after an intravenous injection.
• The enterohepatic circulation, a circulatory system in which an absorbed substance is delivered to the liver for processing before being circulated in the body, was found to play a crucial role in estradiol metabolism in mare.