In investigations on the role of insulin on migration of rat aortic smooth muscle cells, migration of the cells was measured by a modified Boyden chamber technique with 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) as a chemoattractant. Insulin itself was not a chemoattractant for these cells, and insulin added just before the migration assay did not affect cell migration in the presence or absence of 12-HETE.
Cells pretreated with insulin in culture dishes for a long period, however, showed a significant increase in migration induced by 12-HETE, and the increase depended on the insulin concentration: concentrations of insulin of >50 μlU/ml caused about twofold increase in cell migration. On the other hand, long-term incubation with various concentrations of insulin (0.15–1000 μIU/ml) did not affect nonspecific cell migration in the absence of 12-HETE. The stimulatory effect of insulin on cell migration gradually increased with the duration of insulin treatment, reaching a plateau after 4 days. Thus, insulin stimulated 12-HETE-induced smooth muscle cell migration in a time- and dose-dependent manner.
When the extracellular D-glucose concentration in the Boyden chamber was increased from 100 to 300 mg/dl, the stimulatory effect of insulin on 12-HETE-induced cell migration was augmented. This modulation by D-glucose was not due to an increase in the osmotic pressure of the medium, since addition of mannitol to increase the osmotic pressure did not enhance the effect of insulin on cell migration. The present results indicate that insulin in a physiologic or pathophysiologic range stimulates 12-HETE-induced smooth muscle cell migration in a manner dependent on the extracellular D-glucose concentration. These findings are relevant to the increased development of atherosclerosis in subjects with hyperinsulinemia and hyperglycemia, as is seen in obesity and diabetes mellitus.
