Insulin-like activity in goat serum.

Abstract

Partially purified, non-immunoassayable insulin-like activity (NI-ILA) was obtained from goat serum by resin adsorption and elution. When NI-ILA was assayed by an in vivo rat assay, it stimulated glucose-14C uptake into diaphragm glycogen, and epididymal total fat and glycogen. Goat serum and NI-ILA chromatographed on a Sephadex column (G-100) demonstrated: The molecular weight of immunoreactive insulin (IRI) in goat serum was 12,000 with a minor peak at 24,000; NI-ILA was found to have a molecular weight range of 30,000 to 50,000. Glucose administration iv (0.5 g/kgbody weight) led to an increase in IRI; NI-ILA tended to decrease, returning to preinfusion levels within 90 min after glucose administration. Compared to goat NI-ILA alone, incubation of goat NI-ILA with anti-insulin antiserum inhibited 14C uptake into rat diaphragm glycogen, adipose tissue glycogen and adipose tissue total fat. Our studies of insulin-like activity suggest the presence of 2 forms of insulin-like activity in goat serum: an imm...