The Effects of Hypercapnia and Hypoxia on the Distribution of Capillary Blood Flow in the Denervated Intestinal Vascular Bed

Experiments are described which demonstrate that both hypercapnia and hypoxia exert a potent relaxing influence on the resistance vessels of the denervated intestine. The effects on the capillary fluid exchange capacity, as indicated by the capillary filtration coefficient (CFC), are, however, more complex. During local hypoxia CFC increases considerably, probably reflecting a direct relaxing influence on the precapillary sphincter section. In contrast, during hypercapnia CFC decreases in spite of an augmented blood flow. This is assumed mainly to be due to an increased myogenic activity in the same sphincter section, elicited locally by a raised transmural pressure and blood flow. Functional implications of the results are briefly discussed. They suggest that neither high Pco2 accompanied by a low pH, nor low Po2 are of major importance for a functional intestinal hyperemia during digestion.