AJP - Endocrinology and Metabolism, Vol 262, Issue 6 E818-E825, Copyright © 1992 by American Physiological Society
Insulin receptor function is preserved in a physiological state of hypoinsulinemia and insulin resistance
J. Maury, A. F. Burnol, M. Loizeau, T. Issad, J. Girard and P. Ferre
Centre de Recherches sur l'Endocrinologie Moleculaire et le Developpement, Centre National de la Recherche Scientifique, Meudon, France.
The suckling period in the rat is characterized by a continuously low
plasma insulin concentration and a physiological insulin resistance,
particularly in the adipose tissue. This insulin resistance disappears
after weaning on the high-carbohydrate adult diet. We have studied the
number, structure, and function of adipose tissue insulin receptors during
the suckling-weaning transition. The insulin receptor number determined
either on intact adipocytes or after partial purification was higher during
suckling (15 days), whereas the affinity was similar when compared with
weaned rats (30 days). The molecular weight of the alpha- and beta-subunits
were identical in both groups and, when analyzed in nonreducing conditions,
the alpha 2 beta 2-form was the unique detectable form of the receptor.
Neither the basal and insulin-stimulated autophosphorylation of the insulin
receptor beta-subunit nor the tyrosine kinase activity toward a synthetic
substrate was decreased during the suckling period. Thus, in the adipose
tissue of the suckling rat, a marked insulin resistance is concomitant with
a normal insulin receptor number and function.
