PLASMA OESTRADIOL, LUTEINIZING HORMONE AND PROGESTERONE DURING THE OESTROUS CYCLE IN THE BEAGLE BITCH

Abstract

Recent reports have recorded changes in the concentrations of oestradiol-17β, progesterone and luteinizing hormone (LH) in the plasma of the Beagle bitch during the oestrous cycle and pregnancy (Bell, Christie & YoungLai, 1971; Christie, Bell, Horth & Palmer, 1971; Boyns, Jones, Bell, Christie & Parkes, 1972; Jones, Boyns, Bell, Christie & Parkes, 1973). In many species there is evidence which strongly suggests that the ovulatory release of LH is preceded by an increase in plasma levels of oestradiol (Stevens & Vorys, 1967; Labhsetwar, 1970). As part of a study on the control of gonadotrophin secretion in the dog, it was decided to investigate the relationships between the plasma levels of these hormones during pro-oestrus, oestrus and metoestrus. Beagle bitches were maintained under controlled conditions and blood samples were collected between 14.00 and 15.00 h. The duration of pro-oestrus and oestrus was assessed by means of clinical appearance, behavioural studies and