Guanine nucleotide-binding proteins in aortic smooth muscle from hypertensive rats

To explore the hypothesis that altered vascular muscle signal transduction may underlie some of the vascular changes observed in hypertensive models, we measured expression of GTP-binding protein (G protein) alpha-subunits, Gs, G(i), and Gq, in aortic muscle of reduced renal mass and sham-operated rats and proximal and distal aortic segments from rats with interrenal aortic coarctation (IR-AC). G protein expression was measured by immunoblot analysis. When we probed aortic muscle membrane with G(i) and Gq alpha-subunit antibodies, we identified 41- and 42-kD immunoreactive proteins, respectively. Three immunoreactive bands specific to Gs alpha-subunit antibody were resolved. Immunoreactive blot densities were compared. In aortic muscle membrane of reduced renal mass rats (blood pressure, 148 +/- 7 mm Hg), we found significantly reduced Gs and G(i) blot densities compared with sham-operated controls (blood pressure, 99 +/- 12 mm Hg). There were no differences in Gq blot densities between reduced renal mass and control rats. Gs and G(i) blot densities were significantly lower in IR-AC proximal aortic segments (carotid pressure, 165 +/- 5 mm Hg) and distal aortic segments (femoral pressure, 121 +/- 4 mm Hg) than in aortas of sham-operated controls. In contrast, Gq expression was significantly increased in the high-pressure proximal aortic segments compared with low-pressure distal aortic segments from IR-AC rats. Thus, altered G protein expression occurs in aortic muscle from nongenetic rat models of hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)