Effects of partial hepatectomy on hepatic insulinlike growth factor binding protein-1 expression.

Insulinlike growth factor binding proteins modulate the action of the insulinlike growth factors in various bioassays and may regulate the bioavailability of the insulinlike growth factors in vivo. Because the insulinlike growth factors may influence hepatic regeneration, we have examined the effect of partial hepatectomy on serum insulinlike growth factor binding proteins and on the abundance of insulinlike growth factor binding protein-1 messenger RNA in the liver. All rats were fasted before and after partial hepatectomy or sham operation to avoid the confounding effects of difference in food intake. Using a conventional protocol, 70% of the liver was removed, and groups of four or five rats were killed at different intervals after partial hepatectomy. Sham-operated rats served as controls. Pooled sera from each group of rats were analyzed by ligand blotting with 125I-insulinlike growth factor-I. Liver RNA from individual rats was analyzed by slot-blot and Northern-blot hybridization. A small decrease in the 39- to 42-kD insulinlike growth factor binding protein was apparent in sera from both the sham-operated and partial hepatectomized rats. In contrast, a dramatic increase (fivefold) in the 29-kD serum insulinlike growth factor binding protein (insulinlike growth factor binding protein-1) was apparent only in the partial hepatectomized rats. Hepatic insulinlike growth factor binding protein-1 messenger RNA abundance was significantly increased (1.99 +/- 0.18-fold; p less than 0.05) at 1 hr, reached a peak of 2.32 +/- 0.22-fold (p less than 0.01) at 3 hr after partial hepatectomy and returned to basal levels over the subsequent 6 to 12 hr.(ABSTRACT TRUNCATED AT 250 WORDS)