REGULATION OF NA+,K+-ATPASE ALPHA-SUBUNIT ISOFORMS IN RAT-TISSUES DURING HYPERTENSION

We investigated the regulation of the protein expression of the cy isozymes of Na+,K+-ATPase in reference to the enzyme activity in the heart, brain and skeletal muscle of rats during deoxycorticosterone acetate (DOCA)-salt hypertension. Treatment of rats with DOCA and salt for 28 days produced a significant increase in systolic blood pressure compared to the control groups which remained normotensive. Rats treated with DOCA expressed greater amounts of the immunoreactive alpha-1 isoform than untreated controls in whole heart membranes. However, the DOCA-induced increase in the alpha-1 isoform did not occur during DOCA-salt hypertension. There was a parallel change in the enzyme activity of the Na+,K+-ATPase and the protein expression of the alpha-1 isoform as a result of these treatments. We have also demonstrated that the hearts of DOCA-salt hypertensive rats expressed less of the alpha-2 isoform compared to the controls. We could not detect any alteration in the alpha-1 and alpha-2 isoforms of the skeletal muscle and alpha-1, alpha-2 and alpha-3 isoforms of the whale brain Na+,K+-ATPase during salt or DOCA treatments alone or DOCA-salt hypertension. Furthermore, the Na+,K+-ATPase activity was unaltered in these tissues during these treatments. In conclusion, cardiac Na+,K+-ATPase alpha-subunit protein expression appears to be regulated during DOCA-salt hypertension. In the skeletal muscle and brain, tissues not subjected directly to increased pressure, this regulation of the Na+,K+-ATPase was not apparent.