P2 nucleotide receptors play a major role in modulating cell function and are potentially important regulators of renal function. Recently P2 receptor subtypes have been identified in renal cell lines, the renal vasculature and in localised nephron segments (Schwiebert & Kishore, 2001). In the present study, rats were terminally anaesthetised with pentobarbitone sodium (90 mg kg-1 I.P.) in accordance with UK legislation and the right kidney was removed. Immunohistochemistry, using P2 subtype specific antibodies, was used to identify the intrarenal distribution of P2 receptors.
With the exception of P2X7, all the P2 receptor subtypes tested were detected in the rat kidney and these results were reproducible (n = 6). P2X1, P2X2 and P2Y1 were found in the smooth muscle layer of intra-renal vessels. In addition, P2Y1 was also found on the vascular endothelium including glomerular and peritubular capillaries and in late proximal tubules. P2Y2 was found in the glomerular mesangial cells but no other cell type was positive for this P2 subtype. P2X6 was present throughout the renal tubule epithelia from the proximal tubule to the collecting duct. In the cortex, P2Y4 and to a lesser extent P2X4 were found on tubular epithelium. P2X5 was present in the later part of the nephron, in particular the collecting ducts.
The results from the present study clearly demonstrate the presence of P2 receptors in renal vessels, mesangial cells and epithelia of all nephron segments. In other tissues these receptors elicit a wide range of biological effects, including altered ion transport and vascular tone. However, the function of P2 receptors in the kidney is still unclear but they may affect both ultrafiltration at the glomerulus and selective reabsorption or secretion of fluid and electrolytes along the renal tubule.
The MRC and St Peters Trust supported this work.