SODIUM AND POTASSIUM IN THE WALLS OF ARTERIOLES IN EXPERIMENTAL RENAL HYPERTENSION*

Abstract

Fifty-five rats were made hypertensive by narrowing the renal artery of their one remaining kidney. Seven months later these hypertensive rats were divided into two evenly matched groups. The rats in one group were "cured" of their hypertension by releasing the arterial constriction. The rats in the other group had a comparable sham operation. One week after either procedure, a sample of arteriolar tissue from vessels of 0.025 to 0.14 mm outer diameter was obtained. Arterioles from the rats with continuing hypertension had 16% more sodium per unit of dry weight than those from the rats "cured" of hypertension (< 0.0001). The potassium in the arteriolar wall was similar in the two groups and a difference in chloride content was of borderline significance (p = 0.08). At least part of the increment of sodium in the hypertensive arterioles appears to be located intra-cellularly. A 10% increase in the total cation content (Na + K) in the hypertensive arterioles (p=0.0004) may indicate that these vessels have about 10% more water per unit of dry weight than the arterioles from the rats with "cured" hypertension. The articles from the rats with either continuing or "cured" hypertension had undergone about the same degree of thickening; hence the difference in sodium content is probably not related to this. The extra sodium in a hypertensive arteriole may contribute to its narrowed lumen.