Effects of potassium adaptation on blood pressure and pressor responses in normotensive and renal hypertensive Wistar rats.

Potassium adaptation reduces blood pressure (BP) in hypertensive humans and animals but its effects on normotensive BP and the nature of pressor responses to vasoactive drugs are not known. We measured directly, the mean arterial pressure (MAP) of normotensive control, normotensive potassium-adapted (given 0.75% potassium chloride solution for 5 weeks), renal hypertensive (RHP), and renal hypertensive Wistar rats later adapted to potassium. The maximum percentage change, the ED25, and recovery times after bolus injections of noradrenaline (NA), angiotensin II (Ang. II), sodium nitroprusside (SNP), and acetylcholine (ACh) were compared. The MAP of normotensive potassium-adapted rats was significantly lower than that of the normotensive controls (95.6+/-5.0 vs. 110.8+/-2.8 mmHg, p<0.05). The potassium-adapted hypertensive rats (RHP-A) also had significantly lower MAP values than the non-adapted hypertensive ones (116.0+/-4.4 vs. 138.2+/-4.1 mmHg, p<0.01). Potassium adaptation significantly blunted responses to NA and augmented responses to SNP but while the duration of action of Ang. II was significantly shortened, that of SNP was significantly increased. We conclude that potassium adaptation reduces BP in the normotensive and hypertensive rats and may influence both the degree and duration of action of vasoactive drugs given as bolus injections.