A cooperative action of endothelin-1 with prostaglandin F(2alpha) on luteal function in the cow.
Prostaglandin F(2alpha) (PGF(2alpha)) is the primary luteolysin in the cow, and luteal endothelin-1 (ET-1) interacts with PGF(2alpha) during the process of luteolysis. In contrast, a developing corpus luteum (CL) is refractory to exogenous administration of PGF(2alpha). Thus, the present study was aimed to investigate the functional relationship between ET-1 and PGF(2alpha) in the mid-CL (PGF(2alpha)-sensitive) and early-CL (PGF(2alpha)-refractory). In the mid-CL model, cows (n = 6/treatment) were assigned to receive one of five types of treatments on day 10 of the estrous cycle: (1) an injection of saline; control, (2) a 500 microg of PGF(2alpha) analogue (sufficient dose to induce luteolytis); full-PG, (3) an intraluteal injection of 0.25 mg ET-1; ET-1, (4) a 125 micro g of PGF(2alpha) (insufficient dose to induce luteolytis); 1/4PG or (5) an intraluteal injection of 0.25 mg ET-1 after administration of a insufficient dose of PGF(2alpha) analogue; 1/4PG/ET. In the early-CL model, cows were assigned to receive one of two types of treatments on day 5 of the estrous cycle: (1) a sufficient dose of PGF(2alpha) analogue; PG (n = 5) or (2) an intraluteal injection ET-1 after a sufficient dose of PGF(2alpha); PG/ET (n = 7). In the mid-CL model, 1/4PG/ET resulted in a rapid reduction of progesterone (P) concentrations similar to that in full-PG from the next day. However, the levels of P in 1/4PG/ET (1.5-2.5 ng/ml) kept significantly higher than that in full-PG (< 0.5 ng/ml). ET-1 or 1/4PG did not decrease plasma P concentrations (4-6 ng/ml). The plasma ET-1 levels increased with the full-PG administration. In the early-CL model, both treatments had no effect on plasma P increase and ET-1 levels. The overall results indicate that the intraluteal ET-1 injection after administration of insufficient dose of PGF(2alpha) induces the depression of P secretion in vivo during the mid luteal phase in the cow, supporting the concept that ET-1 is one of a local mediator of functional luteolysis in the cow. The result further indicates that the early-CL is not only PG-refractory but also ET-1-refractory.
Shirasuna
K
K
Graduate School of Animal and Food Hygiene, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, Japan.
Watanabe
S
S
Oki
N
N
Wijayagunawardane
M P B
MP
Matsui
M
M
Ohtani
M
M
Miyamoto
A
A
D000818:Animals; D002417:Cattle / Q000502:physiology*; D003008:Cloprostenol / Q000494:pharmacology; D003338:Corpus Luteum / Q000187:drug effects* / Q000502:physiology; D015237:Dinoprost / Q000031:analogs & derivatives / Q000494:pharmacology*; D004347:Drug Interactions; D019332:Endothelin-1 / Q000097:blood / Q000494:pharmacology*; D030762:Estrous Cycle / Q000187:drug effects / Q000502:physiology; D005260:Female; D003341:Luteolysis / Q000187:drug effects* / Q000502:physiology; D011374:Progesterone / Q000097:blood
D019332:Endothelin-1; D003008:Cloprostenol; D011374:Progesterone; D015237:Dinoprost