[Capillary filtration coefficient and the distensibility of the venous vessels of the small intestine in the process of high-altitude adaptation].

In acute experiments on cats, the increase of capillary filtration coefficient and venous distensibility in small intestine was revealed after 3-5, 14-16 and 29-31 days of high altitude adaptation (The Pamirs, 3370 m above sea level), the changes being more obvious (by 78% and 45%, resp.) after 3-5 days in comparison with low altitude control. The effects of noradrenaline on the small intestine precapillary sphincters and venous distensibility were preserved at high altitude, whereas regional blockade of alpha- or beta-adrenoreceptors exerted no effect on the results. The increased capillary filtration coefficient seems to be of great importance in "struggle for oxygen" at high altitude hypoxia, and this obviously depends on the opening of preexisting capillaries.