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Timing of prostaglandin F(2alpha) release episodes and oxytocin receptor development during luteolysis in the cow.

Mann GE, Lamming GE

University of Nottingham, School of Biosciences, Division of Animal Physiology, Sutton Bonington Campus, Loughborough LE12 5RD, UK. George.Mann@Nottingham.ac.uk

The timing of PGF(2alpha) release and the timing and extent of the rise in endometrial oxytocin receptors was determined in relation to the timing of the progesterone fall during luteolysis in cycling cows. In cows undergoing luteolysis (n = 6), measurement of PGF(2alpha) metabolite in hourly plasma samples collected during daily 10 h sampling periods identified a total of 2.2+/-0.5 PGF(2alpha) release episodes per animal, each of 4.0+/-0.4 h duration. In cows in which luteolysis was not observed (n = 4) no PGF(2alpha) release episodes were identified. In a further three cows in which additional repeated uterine biopsies were collected on days 15, 17, 19, 21 and 23, endometrial oxytocin receptors were initially undetectable (<15 fmol/mg protein) but had increased to 120+/-19 fmol/mg protein prior to the initiation of PGF(2alpha) release episodes. Receptor concentrations then continued to increase reaching peak concentrations of 651+/-142 after luteolysis had been completed.

Published 29 May 2006 in Anim Reprod Sci, 93(3): 328-36.
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