We have recently shown that the stimulatory effects of guanine nucleotides and some agonists on adenylate cyclase activity were diminished in aorta and heart sarcolemma (SL) of spontaneously hypertensive rats (SHR). In the present studies we have examined the activity of GTP-binding proteins (G-proteins) at ADP-ribosylation level, by using pertussis toxin (PT) and cholera toxin (CT) at protein level, by using specific antibodies against Gi (inhibitory) and at mRNA level, by using cDNA probes encoding G-proteins. The labeling of Gi by PT was significantly increased in the aorta and heart SL from SHR as compared to their Wistar-Kyoto control rats (WKY). However, no change in the labeling of Gs (stimulatory) by CT was observed in SHR. Furthermore, immunoblotting experiments using AS/7 antibody which reacts with both Gi alpha-1 and showed an increased immunoprecipitation of Gi alpha-2 in heart SL from SHR. In addition, when the expression of G-proteins was probed at the mRNA levels by Northern blot analysis using cDNA probes, the mRNA levels of Gi2 alpha and Gi3 alpha were significantly enhanced in aorta and heart from SHR. However, the mRNA levels of Gs alpha were not altered in SHR. These results indicate that the gene of Gi and not of Gs is overexpressed in heart and aorta from SHR.
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Anand‐Srivastava et al. (1991) studied this question.