Objective To compare the effects or ouabain and digoxin on both the systolic blood pressure and sodium pump a-subunit isoforms gene expression in the aortic smooth muscle of rats. Methods Normal Sprague- Dawley rats were injected with ouabain (20μg·kg-1·d-l,i. p), digoxin (32 μg·kg-1·d-1, i. p)and normal saline once a day, respectively, and indirect systolic blood pressure was recorded once a week. Six weeks later,all the rats were killed and sodium pump α1-,α2-,and α3-subunit mRNA levels were detected in the aortic smooth muscle with reverse transcription polymerase chain reaction（RT-PCR） method. Results The systolic blood pressure of rats infused with ouabain increased significantly at the end of week 6 [l32. 6±9.0 mmHg （1 mmHg = 0. 133 kPa） vs 115. 7 ± 8. 2 mmHg, P <0.01],while no difference of blood pressure was found between digoxin group and NS group （P>0.05）. The expression or sodium pump α-subunit isoforms in aortic smooth muscle was regulated by either ouabain or digox- in:both ouabain and digoxin increased α1- and α3-subunit expression, α2-subunit decreased in digoxin group but un- changed in ouabain group. Conclusion These results suggest that both ouabain and digoxin could regulate sodium pump α-subunit isoform expression, which might be related to the physiological roles or endogenous ouabain and might be responsible for the difference between the pharmacological and toxicological effects or ouabain and digoxin, including their effects on blood pressure.
