Insulin protection against fat cell receptor inactivation by trypsin.

Digestion of white fat cells with 0.25 mg/ml trypsin for 5 min resulted in over 80 % inhibition of the increase in the conversion of glucose to carbon dioxide due to insulin. Incubation of white fat cells with 0.25 U/ml insulin for 1 min prior to treatment with 0.25 mg/ml of trypsin enabled the cells after washing to convert glucose to carbon dioxide in the presence of 0.16 mU/ml insulin to the same extent as control cells. The data suggest that under appropriate conditions insulin can protect the insulin effector system on the fat cell membrane from inactivation by trypsin. (Endocrinology 87: 191, 1970) ALTHOUGH an abundance of data has accumulated describing the many effects of insulin on the regulation of cellular functions, very little is known about the primary interaction of this hormone with the cell surface.