Effects of L-NAME and L-Arg on arterial blood pressure in normotensive and hypertensive streptozotocin diabetic rats.

The present study was designed to examine blood pressure response to nitric oxide synthase-pathway inhibition and stimulation in normotensive and hypertensive diabetic rats. Rats treated with streptozotocin (60 mg/Kg i.p.) developed high blood glucose, polyuria and slow weight gain compared with control. One group of diabetic rats developed hypertension, consequently we studied three experimental groups: control rats (C), normotensive diabetic rats (ND) and hypertensive diabetic rats (HD). Mean arterial pressure (MAP), systolic blood pressure, diastolic blood pressure and heart rate were recorded: baseline time, 30 after L-nitro arginine methyl ester (L-NAME: 1 mg/Kg i.v.) and post L-arginine (L-arg: 250 mg/Kg i.v.) injection. L-NAME induced a significantly increase in MAP in all groups. This enhancement was smaller in diabetic than in control rats. The increase in MAP in HD was significantly lower than that in ND L-arg induced a significantly decrease in MAP in all groups. This decrease was significantly attenuated in diabetic compared with control rats. The degree of hypotension in response to L-arg in diabetic groups was lower in hypertensive than that in normotensive diabetic rats. These data suggest that an impairment of nitric oxide formation could be involved in the development of hypertension in this model.