In vitro assessment of progesterone and prostaglandin E2 production by the corpus luteum in cattle following pharmacological synchronization of estrus
2009
Skarzynski, D.J.(Polish Academy of Sciences, Olsztyn (Poland)) | Siemieniuch, M.J. | Pilawski, W. | Woclawek Potocka, I. | Bah, M.M. | Majewska, M. | Jaroszewski, J.J.
We studied the secretory function of the corpus luteum (CL) in cows following different estrus synchronization protocols. Estrus was synchronized using one (n=4) or two injections (n=5) of prostaglandin Fsub(2alpha) (PGFsub(2alpha); dinoprost), two injections of different analogues of PGFsub(2alpha) (aPGFsub(2alpha)), luprostiol (n=5) and cloprostenol (n=5), at eleven-day intervals, a gestagen implant (norgestomet, n=5, for 10 days) or norgestomet together with a subsequent dinoprost injection on the day of implant removal (n=5). CL samples were collected by ovariectomy on Day 7-8 of the estrous cycle. Luteal strips were stimulated with LH (100 ng/ml) or prostaglandin Esub(2) (PGEsub(2), 10E-6M) for 24 h in culture media. The progesterone (Psub(4)) and PGEsub(2) concentrations in the media were measured by enzyme immunoassay. In the control CL (spontaneous estrus; n=5), LH and PGEsub(2) stimulated Psub(4) and PGEsub(2) (P0.001). The effects of both factors on Psub(4) were reduced in the CL following dinoprost- and cloprostenol-synchronized estrus (P0.05) and were absent in the luprostiol-synchronized CL (P0.05). In the norgestomet-synchronized CL, the stimulatory effects of LH and PGEsub(2) were higher compared with the CL synchronized by aPGFsub(2alpha) (P0.05). Pharmacological manipulation of the estrous cycle using aPGFsub(2alpha) may cause lower Psub(4) secretion. Estrus synchronization inhibited CL sensitivity to luteotropic factors. Therefore, attention should be focused on the estrous synchronization method in both in vivo and in vitro studies of CL functions in cattle.
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