TY - JOUR
T1 - Investigation of the mechanism by which insulin- induced hypoglycemia decreases luteinizing hormone secretion in ovariectomized Ewes
AU - Clarke, I. J.
AU - Horton, R. J.E.
AU - Doughton, B. W.
PY - 1990/1/1
Y1 - 1990/1/1
N2 - Ovariectomized ewes were treated with 100 IU insulin, iv, which caused reductions in blood sugar and plasma LH concentrations. The effect was prevented by the infusion (iv) of glucose, suggesting that neuroglycopenia and not a direct action of insulin was the cause of reduced LH secretion.An iv infusion of naloxone (40 mg/h for 2 h), which commenced 25 min before the insulin injection, blocked the inhibitory effect of insulin on LH secretion, but it did not prevent the decrease in plasma glucose concentrations. In this treatment group and in a group treated only with naloxone, the opioid antagonist significantly stimulated LH secretion.To determine whether CRF might be involved in the insulin - induced decrease in LH secretion, 50 µg CRF were injected into ovariectomized sheep. Despite producing very high circulating concentrations of CRF within 2 min of injection and the stimulation of cortisol secretion during most of the 4-h posttreatment period, plasma LH levels were not affected. In addition, the intracerebroventricular administration of 10 µg CRF or 10 µg CRF plus 10 µg arginine vasopressin (AVP) did not affect LH secretion.These observations suggest that insulin-induced hypoglycemia decreased LH secretion by neuroglycopenia. This may involve an opioidergic mechanism, but does not involve activation of the hypothalamo-pituitary-adrenocortical axis.
AB - Ovariectomized ewes were treated with 100 IU insulin, iv, which caused reductions in blood sugar and plasma LH concentrations. The effect was prevented by the infusion (iv) of glucose, suggesting that neuroglycopenia and not a direct action of insulin was the cause of reduced LH secretion.An iv infusion of naloxone (40 mg/h for 2 h), which commenced 25 min before the insulin injection, blocked the inhibitory effect of insulin on LH secretion, but it did not prevent the decrease in plasma glucose concentrations. In this treatment group and in a group treated only with naloxone, the opioid antagonist significantly stimulated LH secretion.To determine whether CRF might be involved in the insulin - induced decrease in LH secretion, 50 µg CRF were injected into ovariectomized sheep. Despite producing very high circulating concentrations of CRF within 2 min of injection and the stimulation of cortisol secretion during most of the 4-h posttreatment period, plasma LH levels were not affected. In addition, the intracerebroventricular administration of 10 µg CRF or 10 µg CRF plus 10 µg arginine vasopressin (AVP) did not affect LH secretion.These observations suggest that insulin-induced hypoglycemia decreased LH secretion by neuroglycopenia. This may involve an opioidergic mechanism, but does not involve activation of the hypothalamo-pituitary-adrenocortical axis.
UR - http://www.scopus.com/inward/record.url?scp=0025088303&partnerID=8YFLogxK
U2 - 10.1210/endo-127-3-1470
DO - 10.1210/endo-127-3-1470
M3 - Article
C2 - 2201538
AN - SCOPUS:0025088303
SN - 0013-7227
VL - 127
SP - 1470
EP - 1476
JO - Endocrinology
JF - Endocrinology
IS - 3
ER -