Effects of insulin exposure upon the metabolism of rat aortic media: influence of hydrostatic forces.

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Abstract
When added in vitro, insulin exerts little or no effect on the metabolism of arterial media. However, indirect evidence suggests that an in vivo exposure of arterial tissue to insulin stimulates its metabolism. To evaluate the possibility that hemodynamic forces existing only in vivo may account for this difference, we studied the effect of brief (9-minute) exposures to insulin of isolated rat thoracic aorta perfused in situ at low (34 mm Hg = 4.6 kPa) and high (70 mm Hg = 9.4 kPa) static pressures. After perfusion, incorporation of glucose-derived 14C into CO2 and lipids, and production of lactate by incubated aortic tissue, were measured. At low perfusion pressure, insulin did not affect the metabolism of the media but strongly stimulated all aspects of the glucose metabolism of the adventitia. At high pressure, insulin again stimulated the adventitia but now also significantly stimulated (+66%) the synthesis of glucose-derived lipids by the media; production of CO2 and lactate by the media did not increase significantly. These results indicate that insulin directly stimulates at least one pathway of glucose metabolism by the media; and that hemodynamic forces are an important factor in determining the response of aortic media to insulin.