Effect of insulin‐like growth factor‐I on metabolism in bovine mesenteric arteries

The effect of insulin-like growth factor-I (IGF-I) on glucose accumulation, amino acid uptake and incorporation of amino acid into protein was studied in arterial smooth muscle. Accumulation of [14C]glucose, uptake of [14C]alpha-aminoisobutyric acid (AIB) and incorporation of [14C]phenylalanine into protein were measured in intima-media preparations of bovine mesenteric arteries (BMA) incubated with IGF-I for 2, 4 or 6 h. IGF-I (2.2 nmol l-1) increased the accumulation of glucose into BMA after 4 h (P = 0.0079) and 6 h incubation (P = 0.0027) and in a concentration of 22 nmol l-1) also after 2 h (P = 0.015). The uptake of AIB and the incorporation of phenylalanine were increased after 4 h incubation with 2.2 nmol l-1) IGF-I (P = 0.0045 and P = 0.026, respectively). The effects of IGF-I on all of the metabolic parameters were dependent on incubation time and concentration of IGF-I. Concentration-effect curves were determined for the effect of IGF-I and also for insulin on glucose accumulation in BMA incubated for 6 h. The concentration-effect relationships for IGF-I and insulin were very similar with pD2 values of 7.6 +/- 0.2 (EC50 = 27 nmol l-1) and 7.5 +/- 0.2 (EC50 = 34 nmol l-1), respectively. No additive effect of IGF-I and insulin in supra-physiological concentrations (1.0 mumol l-1) could be demonstrated. These results show that IGF-I has metabolic effects which are similar to the effects of insulin in vascular smooth muscle and suggest that IGF-I may be of importance for the metabolism in vascular smooth muscle.