Microautoradiographic Distribution of 14C-Diltiazem in the Dog Kidney after Renal Arterial Injection

The microscopic distribution of 14C-diltiazem in the dog kidney after renal arterial injection was studied by means of microautoradiographic technique. The highest silver grain density existed in the proximal and distal tubules, and the ascending loop of Henle. The definite accumulation of the radioactivity in the distal tubule and the ascending loop of Henle, which are involved in Na-transport, seems to be compatible with the observation that diltiazem affects directly on these segments, thus causing the diuretic action. The presence of radioactivity in the proximal tubule may also suggest that diltiazem has an influence on this tubule and increases the urinary volume.