Inhibition of 3H-1-norepinephrine uptake by ouabain is species dependent.

Tissue slice to medium ratios of 3H-1-norepinephrine (3H-1-NE) were used to study the effect of ouabain on uptake of norepinephrine. The effects of ouabain were studied in slices of heart and spleen from three different species: rat, guinea pig, and dog. The drug produced a species as well as a concentration dependent inhibition of norepinephrine uptake in both types of tissue. In order of decreasing sensitivity, the following relationship between species was observed: dogs greater than guinea pigs greater than rats. Since 3H-1-norepinephrine uptake under the present experimental conditions represents uptake into sympathetic nerve terminals, it was concluded that Na+-K+-ATPases of sympathetic nerve terminals have species dependent differences in ouabain sensitivity similar to those of myocardium.