Site of entry of kininase II into renal tubular fluid.

The stop-flow technique was used to determine the site of entry of kininase II into tubular fluid in dogs. Stop-flow patterns were constructed for kininase II, p-aminohippurate, sodium, and potassium. The proximal tubule was localized by the peak of p-aminohippurate concentration and the distal tubule by the minimum sodium concentration. In the stop-flow pattern for kininase II, three peaks (a, b, and c) were observed. A main peak (a), located 2.25 +/- 0.45 ml distal to the p-aminohippurate peak (p less than 0.01) and 3.75 +/- 0.31 ml proximal to the minimum sodium concentration (p less than 0.001), was observed in all experiments. Peak c, located 2.6 +/- 0.4 ml (p less than 0.01) proximal to the p-aminohippurate peak, was observed in five dogs. Peak b appeared in five dogs and was always located 2.0 ml distal to the minimum sodium concentration. This peak was coincident with the potassium peak. Only two of eight experiments showed all three peaks. These results showed that the major kininase II entry into the tubular fluid is near the p-aminohippurate peak and that distal entry occurred in 63% of the dogs.