INTRARENAL DISTRIBUTION OF ORGANIC OSMOLYTES IN HUMAN KIDNEY

The distribution pattern of renal organic osmolytes in surgically expl anted human kidneys was investigated and compared with that of untreat ed Sprague-Dawley rats (U-osmo = 1186 mosmol/kg H2O). Sorbitol, myo-in ositol, glycerophosphorylcholine and betaine were measured by liquid c hromatography (HPLC) in homogenates of five different kidney zones fro m the cortex towards the papillary tip. All four organic osmolytes wer e detected as in human as in rat kidney. The expected increase from th e inner medulla to the papillary tip for sorbitol and betaine, and fro m the outer medulla to the papilla for glycerophosphorylcholine, was o bserved in rats, but not in explanted human kidney. An inverse distrib ution pattern was observed with decreasing tissue contents from the in ner and outer medulla to the papillary tip for all organic osmolytes a nd urea. This intrarenal osmolyte profile is in accordance with that o bserved during water and lithium diuresis in rats. Therefore it can be assumed that a loss of renal medullary osmolytes during the intra-ope rative treatment of patients led to the observed osmolyte pattern. We conclude that organic osmolytes are involved in renal medullary osmoad aptation of humans.