The intrarenal distribution of urea-¹⁴C as shown by autoradiography

Abstract

By use of an autoradiographic technique sodium and chloride were reported to be distributed in two separate regions in the mammalian kidney, the outer medulla and the papillary tip. Since urea is thought to be the other major component contributing to the overall osmotic pressure of the medulla, a similar pattern to that of sodium and chloride might be expected. Autoradiograms with urea-14C were made from kidneys of rats given a constant infusion of radioactivity and inulin (for the determination of GFR). The urea-14C autoradiograms showed an elevated region of radioactivity in the outer medulla adjacent to a region of lowered deposition in the outer zone of the inner medulla. This latter region was then followed, in the inner medulla, by an increasing deposition of urea-14C towards the papillary tip. This pattern is identical with that previously reported for sodium and chloride, suggesting a similar pattern for the osmotic pressure in the kidney. </jats:p