THE INFLUENCE OF HIGH GLUCOSE-LEVELS AND OR HYPEROSMOLARITY ON RAT ISOLATED AORTA

We investigated the influence of high-glucose levels (30.5 mmol/L) and /or hyperosmolarity on pharmacological responses in aortic ring prepar ations taken from nondiabetic rats. Moderate changes were observed for the concentration-response curves of noradrenaline and phenylephrine, but not for methoxamine and cirazoline. Maximal active forces of the concentration-response curves of potassium chloride and calcium chlori de were significantly reduced by the elevated glucose levels per se, b ut neither the slopes of the curves nor the - logEC50 values were affe cted. Concentration-response curves of serotonin and U 46619 were not affected. For angiotensin II, the -logEC50 values and maximal active f orces of the concentration-response curves were significantly lower un der both hyperglycemic and hyperosmolar conditions. The present study suggests that potential changes in contractile behavior in isolated ve ssels from diabetic animals cannot be attributed to high glucose level s and/or hyperosmolarity as such, but indeed reflect vascular changes associated with the diabetic state. An exception has to be made for th e depolarization of aortic ring preparations of nondiabetic rat; the e levated glucose level leads to an impaired calcium influx via the (slo w) L-type calcium channels.