Somatotrophic receptors in hepatic tissue of the developing male pig

Publisher Website
Google Scholar
Abstract
The development of hepatic somatotrophic receptors and plasma concentrations of insulin-like growth factor-I (IGF-I) were investigated at five different ages (2, 20, 35, 105 and 165 days) in four male pigs per group. The specific binding of 125I-labelled porcine GH (pGH) to hepatic somatotrophic membranes was very low at 2 days of age (0·53±0·12%), and increased progressively (P 125I-labelled bovine GH (bGH) to the same membrane preparations was markedly higher than binding of 125I-labelled pGH; it also showed a distinct developmental increase (P P Ka) of approximately 3·5 litres/nmol. Curvilinear Scatchard plots were observed in the two oldest age groups. The Ka for the higher affinity binding site (approximately 5·0 litres/nmol) was very similar to that for the sole site observed in the younger animals. The Ka of the lower affinity binding site was approximately 0·35 litres/nmol. There was a significant (P r = 0·82, P n = 20) with plasma concentrations of IGF-I. The role of the lower affinity binding site which was observed in addition to the high affinity binding site in older pigs is less clear. The data from the present study support the hypothesis that the postnatal rise in plasma concentrations of IGF-I is associated with the developmental increase of the capacity of the high affinity somatotrophic receptors. Journal of Endocrinology (1989) 123, 25–31