Endocrinology, Vol 127, 1470-1476, Copyright © 1990 by Endocrine Society

ARTICLES

Investigation of the mechanism by which insulin-induced hypoglycemia decreases luteinizing hormone secretion in ovariectomized ewes

IJ Clarke, RJ Horton and BW Doughton
Prince Henry's Institute of Medical Research, South Melbourne, Victoria, Australia.

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 micrograms 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 micrograms CRF or 10 micrograms CRF plus 10 micrograms 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.

This article has been cited by other articles:

				J. D. Veldhuis, J. N. Roemmich, E. J. Richmond, and C. Y. Bowers Somatotropic and Gonadotropic Axes Linkages in Infancy, Childhood, and the Puberty-Adult Transition Endocr. Rev., April 1, 2006; 27(2): 101 - 140. [Abstract] [Full Text] [PDF]

				G. N. Wade and J. E. Jones Neuroendocrinology of nutritional infertility Am J Physiol Regulatory Integrative Comp Physiol, December 1, 2004; 287(6): R1277 - R1296. [Abstract] [Full Text] [PDF]

				S. R. Singh and K. P. Briski Septopreoptic {micro} Opioid Receptor Mediation of Hindbrain Glucoprivic Inhibition of Reproductive Neuroendocrine Function in the Female Rat Endocrinology, November 1, 2004; 145(11): 5322 - 5331. [Abstract] [Full Text] [PDF]

				S. Ohkura, T. Ichimaru, F. Itoh, S. Matsuyama, and H. Okamura Further Evidence for the Role of Glucose as a Metabolic Regulator of Hypothalamic Gonadotropin-Releasing Hormone Pulse Generator Activity in Goats Endocrinology, July 1, 2004; 145(7): 3239 - 3246. [Abstract] [Full Text] [PDF]

				X. F. Li, J. E. Bowe, J. C. Mitchell, S. D. Brain, S. L. Lightman, and K. T. O'Byrne Stress-Induced Suppression of the Gonadotropin-Releasing Hormone Pulse Generator in the Female Rat: A Novel Neural Action for Calcitonin Gene-Related Peptide Endocrinology, April 1, 2004; 145(4): 1556 - 1563. [Abstract] [Full Text] [PDF]

				K. M. Oltmanns, B. Fruehwald-Schultes, W. Kern, J. Born, H. L. Fehm, and A. Peters Hypoglycemia, But Not Insulin, Acutely Decreases LH and T Secretion in Men J. Clin. Endocrinol. Metab., October 1, 2001; 86(10): 4913 - 4919. [Abstract] [Full Text] [PDF]

				S. Ohkura, T. Tanaka, S. Nagatani, D. C. Bucholtz, H. Tsukamura, K.-I. Maeda, and D. L. Foster Central, But Not Peripheral, Glucose-Sensing Mechanisms Mediate Glucoprivic Suppression of Pulsatile Luteinizing Hormone Secretion in the Sheep Endocrinology, December 1, 2000; 141(12): 4472 - 4480. [Abstract] [Full Text] [PDF]

				J. E. Schneider, R. M. Blum, and G. N. Wade Metabolic control of food intake and estrous cycles in Syrian hamsters. I. Plasma insulin and leptin Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2000; 278(2): R476 - R485. [Abstract] [Full Text] [PDF]

				M. J. Cunningham, D. K. Clifton, and R. A. Steiner Leptin's Actions on the Reproductive Axis: Perspectives and Mechanisms Biol Reprod, February 1, 1999; 60(2): 216 - 222. [Abstract] [Full Text] [PDF]

				P. A. Komesaroff, M. Esler, I. J. Clarke, M. J. Fullerton, and J. W. Funder Effects of estrogen and estrous cycle on glucocorticoid and catecholamine responses to stress in sheep Am J Physiol Endocrinol Metab, October 1, 1998; 275(4): E671 - E678. [Abstract] [Full Text] [PDF]

				A. K. Panicker and G. N. Wade Insulin-induced repartitioning of metabolic fuels inhibits hamster estrous behavior: role of area postrema Am J Physiol Regulatory Integrative Comp Physiol, April 1, 1998; 274(4): R1094 - R1098. [Abstract] [Full Text] [PDF]