Regional characterization of G-protein subunits in glomeruli, cortices and medullas of the rat kidney.

We examined the types of guanine nucleotide-binding regulatory (G) protein subunits in isolated glomeruli, cortices excluding glomeruli and medullas of rat kidneys using bacterial toxin-catalyzed adenosine 5'-diphosphate (ADP) ribosylation and specific immunoblots. ADP ribosylation catalyzed by cholera or pertussis toxin revealed the presence of stimulatory G (Gs) or inhibitory G (Gi) proteins in membranes of the 3 segments of the kidney. Immunoblots further demonstrated the existence of several G-protein subunits, two Gs-protein alpha-subunits (G alpha s: 45 and 52 kD), Gi-protein alpha 1, alpha 2 and alpha 3-subunits (G alpha i1, G alpha i2: 40-41 kD, G alpha i3: 40 kD), bacterial toxin-insensitive G-protein alpha q- and alpha 11-subunits (G alpha q/11: 42 kD) and G-protein beta-subunits (G beta: 35-36 kD), in membranes of the preparations. The predominant subspecies of G alpha s was a 52-kD protein in glomerular membranes and a 45-kD protein in membranes of cortices and medullas. All of the G-protein subunits examined, however, were not detected in cytosolic fractions of glomeruli, cortices and medullas. Thus, we conclude that detectable quantities of several G-protein subunits including the new G-protein subunit, G alpha q/11, are present in membranes of glomeruli, cortices not containing glomeruli and medullas from the rat kidney. Both the existence of G alpha i1 and/or G alpha i2 subunits in glomeruli and the presence of G alpha q/11 subunits in the 3 preparations are new evidence.(ABSTRACT TRUNCATED AT 250 WORDS)