Effect of sodium nitroprusside on Na+, K+-ATPase of rat myocardium and renal cortex

The influence of NO donor, sodium nitroprusside (SNP) in concentrations of 10(-5)-10(-3) M, on the Na-pump activity in membrane preparations (microsomes) of rat miocardium and renal cortex was studied. A correlation has been observed between Na-pump activation by 31.4% and 73.6% and increase in thiol group content by 45.0% and 94.0% in native microsomes of myocardium and renal cortex by low concentrations of SNP (10(-5)-10(-4) M). The Na-pump activation as well as the increase in the number of DTNB-reactive thiol groups was abolished after the detergent treatment (0.025% sodium dodecylsulphate); however, the detergent by itself exerted similar influence on Na-pump activity and thiol group content in microsomes. A comparable effect of other oxidants (hydrogen peroxide and nitroglycerine) on SH-group content in microsomes of renal cortex was also shown. A conclusion was made that non-specific oxidative action of SNP on some membrane structures in microsome preparations led to their exposure and activation of the Na-pump by demasking of its latent activity.