Administration of recombinant human insulin-like growth factor I to pigs: determination of circulating half-lives and chromatographic profiles.

Recombinant human insulin-like growth factor I (IGF-I) was injected daily (4 or 8 mg/pig) as an intra-arterial bolus into pigs for 3 consecutive days and the serum IGF-I concentration was measured to determine disappearance profiles. IGF-I partitioned to a fast component (half-life, t 1/2 = 5.7 min) and a slow component (t 1/2 = 253 min) in pig serum. Chromatography of serum revealed that the fast component comprised unbound IGF-I, whereas the slow component comprised IGF-I bound to 40- and 150-kD serum IGF-binding proteins. In addition, administration of exogenous IGF-I caused significant hypoglycemia.