Stevenson K R, Parkinson T J, Wathes D C
Department of Anatomy, School of Medical Sciences, Bristol, UK.
J Reprod Fertil. 1991 Nov;93(2):437-41. doi: 10.1530/jrf.0.0930437.
Jugular venous blood samples were collected throughout a complete oestrous cycle from 9 mares for measurement of progesterone and oxytocin by radioimmunoassay. Mean oxytocin concentrations remained at approximately 1 pg/ml throughout, with no evidence of cyclic variation in the release pattern. Extracts of corpus luteum and follicles obtained from a further 33 mares at different stages of the cycle all contained oxytocin concentrations of less than 10 pg/g wet weight of tissue. We conclude that the ovaries are not a source of circulating oxytocin during the oestrous cycle in this species. The plasma oxytocin concentrations reported here are substantially lower than those found by other groups.
