Cloning of the α-Subunit of Gs Protein From Spontaneously Hypertensive Rats

Enhanced sodium reabsorption by the kidney has a significant role in the development of genetic hypertension. In the spontaneously hypertensive rat (SHR) model of genetic hypertension, the enhanced sodium reabsorption likely arises from abnormal hormonal regulation of tubular transport. Since hormonal signaling pathways are coupled frequently via GTP binding proteins, one explanation for hormonal abnormalities in SHR would be a defect in a GTP binding protein or proteins. Recent work has suggested that the regulation of Na, K- ATPase activity by cholera toxin-sensitive GTP binding proteins is abnormal in SHR. The purpose of the present studies was to clone the αs-subunit, which is the subunit ADP ribosylated by cholera toxin, of Gs protein to determine whether it is abnormal in SHR. Reverse transcription-polymerase chain reaction was able to detect mRNA for αs in both Wistar-Kyoto (WKY) rats and SHR. Northern analysis indicated that equivalent amounts of αs mRNA were present in WKY rats and SHR. S1 nuclease analysis demonstrated that there was no difference in the amount of αs short and long forms between WKY rats and SHR. Subcloning and sequencing of polymerase chain reaction products from WKY rats and SHR indicated that the αs forms present in renal cortex were identical. ADP ribosylation studies with cholera toxin demonstrated the presence of equivalent amounts of αs protein in WKY rats and SHR. Taken together, these results suggest that the abnormal regulation of Na+,K+-ATPase activity by a cholera toxinsensitive pathway in SHR does not arise from a defect in the αs-subunit.