Rubidium86 Clearance during Neurogenic Redistribution of Intestinal Blood Flow

Arterio‐venous extraction of rubidium86 was recorded in the intestine of the cat, using two different administration techniques; and the capillary transport coefficient, PS, was calculated. In all experiments intestinal blood flow resistance was calculated, and in some the capillary filtration coefficient, CFC. These two methods to determine the capillary surface area open to blood flow were well correlated, but the total range for variations for PS was less than for CFC. This difference was explained by the fact that exclusion of some part of the capillary circulation by the precapillary sphincters causes the filtration to cease much more completely than the diffusion. Therefore, CFC seems to better reflect the changing capillary surface area than PS. During the “autoregulatory escape”, the typical vascular response to stimulation of the vasoconstrictor fibres, PS was decreased but in most cases much less so than CFC. These results seem to exclude involvement of true arteriovenous shunts to any significant degree during activation of the vasoconstrictor nerves. If the redistribution of blood flow from the mucosa towards the submucosa during the “autoregulatory escape” utilizes special low‐resistance channels, these must allow for exchange of solutes, implying a situation of “physiological shunting” rather than “true‐shunting”.