Characterization of G proteins in obstructed kidneys

Urinary tract obstruction has a marked effect on renal function. Activation of phospholipases which results in incremental production of vasoactive eicosanoids may contribute to the hemodynamic changes characteristic of an obstructed kidney. G proteins play an important role in transmembrane signal transduction, which control phospholipase activities and eicosanoid production. The present study was designed to determine the presence of G proteins in obstructed kidneys in rats, and to characterize the differences between unilateral ureteral obstruction (UUO) and bilateral ureteral obstruction (BUO).

Several G-protein alpha subunits (G alpha s, G alpha i1,2, and G alpha i3) and the beta subunit (G beta) were determined by immunoblotting and immunocytochemical techniques using specific antibodies against these G proteins.

Immunoblots demonstrated a decreased G alpha i3 content in the outer medullary tubules and a significantly lower G beta level in the glomeruli of UUO. In BUO, there was an increased level of G beta in the cortical tubules, and the G alpha s level was markedly reduced in the inner medullary tubules. Immunocytochemical studies revealed that these G proteins were predominantly localized in the brush border side of the cortical tubules. However, we could not demonstrate staining differences between UUO and BUO.

These results indicate that a modulation of G-protein-coupled transmembrane signal transduction may contribute to the renal functional changes in an obstructed kidney. A different level of expression of G-protein subunits between UUO and BUO may be a factor in the differences of hemodynamics and renal tubular damage between UUO and BUO.