Abstract: Renomedullary interstitial cell （RIC） in the renal papilla was speculated as the source of a mediator （Med-I） with antihypertensive function. In this experiment 4 isolated right kidneys from normal Wistor rats were perfused with MEM culture medium under an elevated pressure . and RIC of both perfused and non-perfused kidneys were studied by electron microscope. The diameter and number （granules /area ） of lipid droplets in non-perfused and perfused kidneys were 0. 52 ±0. 17 μm,24. 9±1.0/1000 μm2 and 0. 45±0. 16μm. 14. 3±3. 3/1000μm2 respectively. These findings proved that the number and size of the lipid droplets of RIC were decreaspd under elevated pressure per fusion and Med-I secretion could be promoted by arterial hypertension.