USE OF MICROSPHERES TO MEASURE SMALL INTESTINAL VILLUS BLOOD-FLOW IN THE DOG

The accuracy of using 7-10 .mu.m microspheres to measure blood flow to canine small intestinal villi was studied. These spheres appear to pass unimpeded through the afferent arterioles of the villus and lodge at the villus tip because virtually all villus spheres were located at the tip, flow determined by visually counting spheres did not differ significantly from flow determined from radioactivity of the sheared-off villus layer, the size distribution of spheres in the villus and subvillus layers was virtually identical to that administered, indicating no premature impaction of the larger spheres and spheres lodging in the submucosa during vasoconstriction did not subsequently migrate to the villi during vasodilatation. Studies with 25 .mu.m spheres indicated that 28% of the 7-10 .mu.m spheres shunted through vessels > 10 .mu.m in diameter. Double isotope studies showed that lodged spheres do not migrate and that the injection of 2-4 .times. 106 spheres does not alter villus flow.