OVULATION RATE AND THE CONCENTRATIONS OF GONADOTROPINS AND METABOLIC HORMONES IN EWES INFUSED WITH GLUCOSE DURING THE LATE LUTEAL-PHASE OF THE ESTROUS-CYCLE

The positive relationship between nutrition and ovulation rate was inv estigated in sheep infused intravenously with glucose. Ovulation rate increased (2.0 +/- 0.0 vs 2.4 +/- 0.3) when ewes were given an infusio n of glucose (60-65 mM/h) for five days in the late luteal phase of th e oestrous cycle. The effect of glucose was obtained without any signi ficant change in LH secretion. The concentration of FSH in glucose-inf used ewes was lower during the infusion (luteal phase) but higher duri ng the early follicular phase. These data suggest that the change in o vulation rate occurred without increased gonadotrophin support to the follicle during the late luteal phase, which is the period of the shee p oestrous cycle during which improved nutrition increases ovulation r ate. There were no changes in GH or prolactin, but changes in circulat ing glucose and insulin levels were detected. We conclude that insulin , because of its role in cell growth and metabolism, is involved in me diating ovulation responses to nutritional stimuli, either directly or more likely by the stimulation of insulin-mediated glucose uptake.