[Insulin-like growth factor I--a connecting link between nutrition and growth].

The influence of an increasing protein supply in combination with soybean oil upon the IGF-I concentration in the serum in correlation with growth was measured on 8 x 10 male Wistar rats. With a casein content of 0% in the food, the IGF-I level was 0.13 +/- 0.02 rU/ml. An IGF-I plateau of 0.74 +/- 0.07 rU/ml was reached at some 15% casein. The additional application of 3% soybean oil increased the IGF-I concentration significantly (P less than 0.01) up to 0.95 +/- 0.16 rU/ml. The investigations show a specific increase of the IGF-I synthesis by the addition of oil, which is paralleled by a further stimulation of the growth of the rats. The nutrition-dependent IGF production in the peripheral tissues (mainly liver) represents the connection link between the growth hormone axis (genetically potential growth) and the growth realizable depending on the supply with nutrients.