[Direct effect of hypoxia on the functions of the small intestinal vessels of the cat].

In anesthetized cats, artificial ventilation with 18, 14 and 8% O2 mixtures decreased the arterial blood pO2 from 104 to 85, 69 and 38 mm Hg, resp. Resistance of the intestine vessels and their capacity decreased in 14 and 8% O2; the capillary filtration coefficient increased at all levels of hypoxia whereas distensibility of veins and mean capillary hydrostatic pressure practically did not alter. A significant diminishing of constrictor responses of the intestine arterial vessels to noradrenaline only occurred in 8% O2. Precapillary sphincters are much more sensitive to O2 deficiency than other portions of the intensive vascular bed but their responsiveness to noradrenaline does not alter even in grave hypoxia.