THE SEQUENCE, TIME, AND DURATION, OF THE RELEASE OF FOLLICLE-STIMULATING HORMONE AND LUTEINIZING HORMONE IN RELATION TO OESTRUS AND TO OVULATION IN THE SHEEP

Abstract

SUMMARY A difference in the timing of the release of follicle-stimulating hormone (FSH) and of luteinizing hormone (LH) from the pituitary of the sheep at about the time of the ovulatory discharge is described. The FSH content of the ovine pituitary began to decrease 8 hr. before the onset of oestrus, by which time 28 % of the FSH content of the pituitary had been discharged. The discharge of FSH continued at a steady rate until 6 hr. after the onset of oestrus to result in a further decrease of 24%. No change in the LH content of the pituitary occurred during the 12 hr. before the onset of oestrus. The discharge of LH started at the onset of oestrus and was completed within 6 hr. by which time 52 % of the LH in the pituitary had been released. The significance of these findings in relation to oestrus and to ovulation is discussed.