Measurement of 42K concentration in the mucosal portion of the intestine without tissue samples: an approach to the measurement of mucosal blood flow in the dog.

SUMMARY 1. The concentration of 42K within the jejunal mucosa was measured by intraluminal miniature Geiger-Muller tubes shielded with platinum foil. 2. Isotope concentration measured by tissue assay of jejunal mucosa gave similar results to that obtained by the Geiger-Muller tubes. 3. Isotope measurement by shielded Geiger-Muller tubes obviates the need for tissue samples and permits repeat measurement in the same animal. This should find physiological application in measuring the mucosal portion of total intestinal blood flow by the indicator fractionation technique.