Bilateral ureteral obstruction alters levels of the G-protein subunits Gαs and Gαq/11

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To evaluate the effects of bilateral ureteral obstruction (BUO) on the levels of G-protein subunits in glomeruli, we examined the types and amounts of G-protein subunits in glomerular membranes from sham-operated control (SOC) rats and rats with BUO of 24 hours duration utilizing bacterial toxin-catalyzed ADP-ribosylation and specific antibodies. ADP-ribosylation catalyzed by cholera or pertussis toxin demonstrated the presence of Gs and Gi proteins in glomerular membranes. Immunoblots further revealed the existence of two types of G alpha s (45 and 52 kDa), as well as G alpha i2 (40 kDa), G alpha i3 (41 kDa), G alpha q/11 (42 kDa) and G beta (35 to 36 kDa) in glomerular membranes. The predominant subspecies of G alpha s was the 52 kDa protein. Detectable amounts of G alpha o were not found in glomerular membranes. Moreover, G-protein subunits were not detected in cytosolic extracts of glomeruli. Both forms of G alpha s and G alpha q/11 were significantly reduced in glomerular membranes from rats with BUO when compared to SOC rats. No significant difference in total G alpha i, G alpha i2 and G alpha i3 and G beta content was observed between the two groups of rats. In vivo pretreatment of rats with simultaneous administration of the angiotensin-converting enzyme inhibitor, enalaprilat, and the thromboxane synthase inhibitor, OKY-046, maintained the amount of G alpha s and G alpha q/11 in rats with BUO at the levels seen in SOC rats. The two drugs did not affect the amounts of G-protein subunits in glomerular membranes of SOC rats.(ABSTRACT TRUNCATED AT 250 WORDS)