The effects of alteration of CO2 and pH on intestinal blood flow in the cat.

1. The effect of alteration of arterial blood pH on intestinal blood flow in the cat has been determined under conditions of constant perfusion pressure.2. Arterial blood pH was altered over the range 7.12-7.70 by infusion of acid and alkali. When end-tidal CO(2) was held constant, there was no change in intestinal blood flow.3. When arterial blood pH was altered over the range 7.19-7.55 by the administration of CO(2) at constant respiratory volume and rate, flow increased with increasing CO(2).4. The intestinal vascular bed was less responsive to noradrenaline at pH 7.2 than at pH 7.6. The change in sensitivity was evident when end-tidal CO(2) was controlled and depended therefore on a change in hydrogenion concentration.5. The dilator effect of CO(2) did not depend upon alteration of sensitivity to noradrenaline since it was seen after adrenergic blockade.