Acute stimulatory effects of prostaglandin F2 alpha on serum progesterone concentrations in pregnant and pseudopregnant pigs.
The objective of this study was to investigate whether PGF2 alpha, administered to pregnant and pseudopregnant gilts in vivo, would cause an acute increase in serum progesterone concentrations prior to luteolysis. Pregnant (n = 9) and pseudopregnant (n = 4) gilts were fitted with a jugular vein cannula on day 40, were treated with 3 ml vehicle (control) i.m. on day 42 and with 15 mg PGF2 alpha on day 45. Blood samples were collected at frequent (5 and 15 min) intervals from 1 h before until 1 h after control and PGF2 alpha injections, at 15 min intervals for 4 h, and then at 5, 6, 9, 21, 33, 45 and 57 h post injection. Progesterone was measured by radioimmunoassay (RIA) in all samples. Porcine LH was measured by RIA in samples collected frequently in the 1 h pre- and 1 h post-injection periods. Serum progesterone concentrations were unchanged in both pregnant and pseudopregnant animals in response to control injection on day 42. However, in both pregnant and pseudopregnant gilts, PGF2 alpha injection on day 45 resulted in an acute increase (approximately 75-80% above pre-treatment levels; p less than 0.05) in serum progesterone lasting approximately 1 h, followed by a return to pre-treatment levels by 2 h, and then a decline to 1 ng/ml or less by 45-57 h (pregnant) or 21-57 h (pseudopregnant), associated with luteolysis. Serum LH concentrations were unchanged between 1 h pre- and post-treatment periods in response to either control or PGF2 alpha-treatment, in both pregnant and pseuodpregnant gilts. These results indicate that PGF2 alpha-injection produces a rapid and transient increase in serum progesterone concentrations which may result from a rapid and direct stimulatory action of PGF2 alpha on porcine luteal cell progesterone synthesis/secretion in vivo.
Gadsby
J E
JE
Department of Anatomy, Physiological Sciences and Radiology, College of Veterinary Medicine, North Carolina State University, Raleigh 27606.
Smith
C A
CA
Almond
G W
GW
D000818:Animals; D015237:Dinoprost / Q000494:pharmacology*; D005260:Female; D007700:Kinetics; D007986:Luteinizing Hormone / Q000097:blood; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000097:blood*; D011374:Progesterone / Q000097:blood*; D011555:Pseudopregnancy / Q000097:blood*; D012016:Reference Values; D013552:Swine
D011374:Progesterone; D007986:Luteinizing Hormone; D015237:Dinoprost