Basically, renomedullary interstitial cells (RMICs) are full of lipid droplets (LDs), which have been thought to be the source of vasodilators. Previous studies have indicated that the renomedullary interstitial cells of the renal papilla can secrete medullipin, which is a vasodilator that suppresses sympathetic tone, causes diuresis and natriuresis and apparently has a suppressive effect on the central nervous system. However, the chemical characteristic of medullipin is still unknown. Aim of this study was the identification of LD proteins based on purification of rat RMICs’ lipid droplet followed by proteomic analysis using 2D-LC-MS/MS technics. To enhance the validity of the data, only proteins with at least two unique peptides were accepted. We found over 300 RMICs’ LD associated proteins. Among these proteins, 92 proteins have been reported to be LD proteins in previous studies, 17% were associated with lipid metabolism and 15% were associated with mitochondria, suggesting close interactions of LDs with mitochondria, and that LDs were involved in metabolism of triglycerides, fatty acids, phospholipids, and sterol esters. We also found enzymes involved in arachidonic metabolism including CYP4F5, CYP4F6, CYP2E1 and CYP2A3, previous study report that LDs are specific sites of novo formation of LTC4 and PGE 2 in leukocytes, suggesting LDs in RMICs may also involved in regulating eicosanoid formation. The difference in the morphology and protein profile of LDs in renal medulla of SHR (spontaneously hypertensive rat) and Wistar-Kyoto(WKY) rats were further analyzed. Electron microscopy revealed more LDs in renal medulla of SHR than in that of WKY rats. Proteomic analysis revealed 15 differently expressed proteins in renal medulla of SHR when compared with WKY rats. Western blot further confirmed that the expression of clathrin and CYP4A3 were upregulated , whereas the expression of UBXD8 was downregulated in renal medulla LDs of SHR. In conclusion, these preliminary results have suggested that LDs in RMICs are rich in many enzymes involving lipid metabolism and blood pressure regulation. To further study the biological function of these proteins in LDs will shed light on the understanding of the mechanisms of high blood pressure.