Intramural Blood Flow and Blood Volume in the Small Intestine of the Gat as Analyzed by an Indicator‐Dilution Technique

The mucosal red cell and plasma flow and volume in the cat small intestine were studied at various levels of smooth muscle vascular tone by means of an indicator‐dilution technique. 32P‐labelled red cells and plasma particles as well as 198Au‐labelled colloid particles were used. The monitored tissue region includes when using 32P most of the mucosa, while only the villi were “seen” with 198Au. During “rest” (total intestinal blood flow about 25 ml/min × 100 g) “mucosal” plasma flow was somewhat lower than total intestinal blood flow while “villous” plasma flow was of the same order of magnitude. “Mucosal” and “villous” plasma volumes measured about 2.0 and 1.5 ml/100 ml, respectively. As the intestinal vascular bed was maximally dilated (total intestinal blood flow 200–250 ml/min × 100 g) by an i.a. infusion of isopropylnoradrenaline, “villous” plasma flow increased to 275 ml/min × 100 ml tissue while “mucosal” blood flow was the same as total intestinal flow. Concomitantly, “mucosal” and “villous” plasma volumes increased to 3.0 and 4.0 ml/100 ml, respectively. Mean transit time through the villous hairpin loop decreased from 5–6 s at rest to about 1 s at maximal vasodilatation.