Studies on the renal uptake of vitamin D3 in the mouse and the quail

The renal uptake of labelled vitamin D3 was studied in the mouse and the quail. Upon the administration of labelled vitamin D3 autoradiographic experiments showed a specific accumulation of radioactivity in the proximal tubuli of the mouse kidney. This was still obvious 18 days after the administration. In the quail, on the other hand, the uptake in the kidney did not exceed the level of the blood. In the mouse there was a slow increase in the amount of steriod in the kidney after the injection of vitamin D3, a maximum being reached 24 hours after the administration. The amount of steroid which accumulated in the kidney was largely proportional to the injected dose of the vitamin-from doses at 4.8 ng to 4.8 mug. Column chromatography showed that most of the renal vitamin D3, was present in a non-metabolized form. Cellular fractionation showed that most radioactivity in the kidney was present in the mitochondrial and microsomal fractions. Upon sonication of the fractions most radioactivity was still bound to these particles.