Are cardiac G-proteins altered in rat models of hypertension?

To determine whether alterations in cardiac G-protein number or function, or both, are involved in the desensitization of adenylate cyclase responsiveness in the hypertensive state.

Quantitation of G-protein subunits in myocardial membranes from four different rat models of hypertension in comparison with respective normotensive rats.

We compared male and female adult spontaneously hypertensive rats (SHR) with age- and sex-matched Wistar-Kyoto (WKY) rats, rats from the highest-pressure quartile from an F2 generation of WKY x SHR hybrids with those from the lowest-pressure quartile, and one-kidney, one clip renal hypertensive with sham-operated rats. The function of Gs alpha was quantitated by reconstitution of cardiac cholate extracts into cyc- cell membranes with subsequent measurement of NaF-stimulated adenylate cyclase activity. The amounts of immunodetectable Gs alpha, Gi alpha, Gq alpha and G beta were determined from quantitative Western blotting experiments with [125I]-protein A detection.

None of the parameters investigated differed significantly between hypertensive and normotensive rats in any of the models investigated.

We conclude that major quantitative alterations in cardiac Gs, Gi or Gq are not a general feature of the hypertensive state.