The Effect of Inosine on Blood Pressure in the Rat 1

Summary

Adenosine and the adenine nucleotides decrease BP by direct vasodilatation. Adenosine is metabolized in vivo to inosine, the concentration of which is known to rise in exercising skeletal muscle and its venous effluent. Inosine is believed to be without effect on blood pressure although a positive myocardial inotropic effect has been suggested.

The present study concerns the influence of metabolic breakdown products of the adenine nucleotides on arterial pressure in the intact rat. BP was measured by direct arterial cannulation during the intravenous administration of inosine, inosine monophosphate (IMP), hypoxanthine, and ribose-1-phosphate. Inosine (0.75-0.85 μmoles/kg) caused a 16% elevation of mean BP. IMP caused a similar increase in BP; hypoxanthine and ribose-1-phosphate were inactive. BP rise after inosine persisted despite parasympathetic, sympathetic or selective α- and β-adrenergic blockade. There was no change in heart rate. Inosine, therefore, elevates BP in the rat by a mechanism which appears to be independent of the autonomic nervous system.