Oxytocin (OT), progesterone and prostaglandin F(2α) (PGF(2α)) concentrations were measured in the utero-ovarian vein (UOV) of ewes which displayed persistence of the corpus luteum (CL). During the period of expected luteolysis, the frequency of OT and PGF(2α) pulses in the UOV was significantly (P < 0.005 for both) lower in ewes with persistent CLs, compared with ewes than underwent normal luteal regression. In contrast, the amplitude of both OT and PGF(2α) pulses was similar in both groups of animals. It is suggested that persistence of the CL resulted from a decreased PGF(2α) pulse frequency, which may have arisen from a decreased frequency of stimulation by OT. In two persistent CL ewes, however, it appeared that a failure at the level of the uterus may have contributed to the observed decrease in PGF(2α) release. Although a PGF(2α) analogue (Lutalyse) infusion into the uterine vein of two ewes with persistent CLs failed to induced luteolysis, it did stimulate a large release of OT into the UOV. This suggests that persistent CLs maybe more resistant to PGF(2α) and, that at day 22 post-oestrus, these CLs are capable of releasing large quantities of OT into the UOV.
|Number of pages||9|
|Publication status||Published - 1 Jan 1987|