Effect of Prostaglandin E2 and F2α on Serum Luteinizing Hormone, Testosterone and Prolactin in Bulls

The effect of intramuscular injections of PGF2α and PGE2 on concentrations of testosterone, luteinizing hormone and prolactin were examined in 1-year-old bulls. Jugular venous blood was sampled from indwelling cannulae at frequent intervals before and after injecting 0, 5, 15 or 30 mg PGE2 or 30 mg PGF2α in five bulls. Treatments were administered in a Latin-square design. Both PGF2α and 30 mg PGE2 caused increased serum prolcatin concentrations within 10 min; prolactin concentrations remained elevated longer after PGF2α than after PGE2. Peak prolactin after 15 mg was only half that after 30 mg PGE2 and the change in prolactin was not significant after 5 mg PGE2. While PGF2α caused significant elevations in serum testosterone and luteinizing hormone (LH), each of these hormones was depressed for 4 to 5 hr by each dose of PGE2. Normal episodic secretion of LH and testosterone resumed within 8 hr after PGE2 treatment. We conclude PGE2 acutely inhibited release of LH.