RESUMEN
Interaction of [125I]-insulin with intact hepatocytes and its correlation with circulatory insulin level was examined. The hepatocytes from new-born rats bound lowest amount of [125I]-insulin (1.39±0.41 pM/mg cell protein) when circulatory insulin level was high (8±1.5 μU/ml). Hepatocytes from 7 day and 21 day old animals demonstrated a more or less similar relationship, Cells from 31 day old animals exhibited maximum insulin binding, activity (5.13±0.18.pM/mg cell protein) against a low serum insulin level (4.25±0.25 μU/ ml). Scatchard analysis of insulin binding shows that the affinity is higher in the hepatocytes from new-born animals than in the hepatocytes of 31 day old animals. Higher binding observed in the latter case may be due to a greater number of binding sites. Hepatocytes from one year old rats bound very little insulin (2.50±0.36 pM/mg cell protein) against a high circulatory insulin level (9.25±0.85 μU/ml). In view of these results, it appears that the down-regulation hypothesis holds true during ontogeny too.