Augmented vascular responses to ouabain in SHRSP during salt loading

Area of Science:

• Cardiovascular Physiology
• Renal and Vascular Physiology
• Hypertension Research

Background:

• High salt intake is a known risk factor for hypertension.
• The specific impact of high salt diets on vascular Na-K pump activity in hypertension remains unclear.
• Stroke-prone spontaneously hypertensive rats (SHRSP) serve as a model for studying salt-sensitive hypertension.

Purpose of the Study:

• To investigate the effect of a high salt diet on sarcolemmal Na-K pump activity in resistance vessels of SHRSP.
• To compare these effects in normotensive Wistar-Kyoto rats (WKY).

Main Methods:

• Isolated hindquarters perfusion technique was used in SHRSP and WKY rats.
• Rats were subjected to either a normal (0.3% NaCl) or high (8% NaCl) salt diet for two weeks.
• Vascular responses to ouabain (a Na-K pump inhibitor) were measured.

Main Results:

• Salt loading increased arterial pressure and augmented ouabain-induced vasoconstriction in SHRSP.
• In WKY rats, salt loading did not affect arterial pressure or vascular responses to ouabain.
• Neither structural vascular changes nor altered norepinephrine release explained the augmented ouabain response in salt-loaded SHRSP.

Conclusions:

• High salt diet appears to augment sarcolemmal Na-K pump activity in hindquarters resistance vessels of SHRSP, but not WKY rats.
• This augmented Na-K pump activity may serve as a compensatory mechanism against salt-induced vasoconstriction in SHRSP.