Abstract

Preincubation of rat adipose tissue and hemidiaphragm with nethalide, an adrenergic blocking agent, inhibits the effect of insulin on glucose uptake and ¹⁴CO₂ production from ¹⁴C-labeled glucose. With the use of ¹³¹I-labeled insulin, it is possible to demonstrate that blocking of the metabolic effects of insulin is not accompanied by any reduction in ¹³¹I bound by the tissue. Addition of guinea pig anti-insulin serum does not affect the proportion of bound radioactive material when rat adipose tissue is incubated with radioinsulin, but markedly reduces insulin binding to rat diaphragm muscle. Incubation of the fat pad with radioinsulin for 90 min reduces the proportion of immunologically active insulin in the medium by about 10%. Experiments described indicate a lack of correlation between the metabolic effects of insulin and the binding of this hormone to tissues.