Short term regulation of endothelial Na+-K+-pump activity by cGMP: a Cs-133 magnetic resonance study

The effect of nitric oxide radicals (NO) on the activity of porcine aortic endothelial Na+-K+-ATPase is reported. Measurements were made using an in v itro cell system and Cs-133 magnetic resonance (NMR). It is shown that NO, through stimulation of guanylate cyclase, results in a reduction of pump ac tivity. Similar observations were made using 8-Br-cGMP. Measurement of the cytosolic volume indicated no changes in volume during incubation with 8-Br -cGMP. Our measurements indicate a continuous regulation of endothelial Na-K+-ATPase activity by endogenous NO. This regulation could be removed by L -NAME, resulting in a small increase in pump activity.