Role of the liver in regulating somatomedin activity: effects of streptozotocin diabetes and starvation on the synthesis and release of insulin-like growth factor and its carrier protein by the isolated perfused rat liver.

Abstract

This report describes the use of 12-h isolated liver perfusions to examine the effects of experimental diabetes mellitus or starvation on the synthesis/release of somatomedin activity, insulin-like growth factor (IGF), by the liver of the adult male Sprague-Dawley rat. Diabetes was induced by the iv injection of streptozotocin (80 mg/kg BW). One group of diabetic liver donors was untreated for 6–8 weeks; a second and third groups of diabetic rats were treated with protamine zinc insulin (2–3 U daily) for periods of 6–8 weeks and 8–9 months, respectively. At the close of these time periods after the onset of diabetes, livers were perfused, and the net cumulative release of IGF and its carrier protein (CP) into perfusates was calculated from analyses of the perfusates by competitive protein-binding assay. The net cumulative synthesis/release of IGF (mean ± SEM, expressed as microunits per 300 cm2 body surface area of donor rat) by livers from untreated diabetic rats (116 ± 94) was profoundly decreased to le...