Cerebral vascular autoregulation of blood flow and tissue PO2 in diabetic rats.

The effect of chronic, severe diabetes mellitus on the morphology, blood flow regulation, and tissue PO2 of the cerebral cortex was evaluated in adult rats. The arterioles of the diabetic animals were enlarged in terms of both lumen diameter and vessel wall area. Although resting blood flow in the diabetic rats was greater than in the normal rats, the autoregulation of cerebral blood flow was very good within an arterial pressure range of 40-150 mmHg, just as in normal rats. The resting tissue PO2 in diabetic rats was 14.9 +/- 0.5 (SEM) compared with 12.7 +/- 0.6 mmHg in normal animals and in both groups remained at or near the resting PO2 at arterial pressures from 40 to 150 mmHg. There was no apparent loss of arterioles on the cortex surface or change in length of individual arterioles in diabetic animals but there was a 20-30% decrease in the number of venules and no change in the length of individual venules. These data indicate that although the arteriolar morphology and number of venules change in the brain during diabetes, physiological function in terms of tissue PO2 and blood flow regulation is maintained within normal limits.