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Alterations in active Na-K transport during mineralocorticoid-salt hypertension in the rat
Abstract:
Studies have been conducted to determine which, if any, of the parameters governing active Na-K transport (K and/or ouabain sensitive) are altered in vascular smooth muscle during mineralocorticoid-salt hypertension. Rats with one kidney removed were treated with either aldosterone or deoxycorticosterone acetate plus saline for 3-4 wk. Ion transport was measured in arteries incubated in a physiological salt solution for periods of 4-6 h. Increased active Na efflux was observed in femoral arteries and aortas from the hypertensive group. This alteration resulted primarily from an elevation in the saturation or maximal capacity of the active transport mechanism, which operated with no significant change in cell Na concentration. The transport parameters related to ion selectivity, cooperativity, and temperature dependence were not significantly altered. Measures of active Na efflux and K influx in the same aortic strips indicated that both fluxes were elevated in the hypertensive group. The ratio of Na to K for active transport was significantly greater than one but was unchanged in the hypertensive rats. These studies provide evidence for the electrogenic operation of the Na-K pump in arterial smooth muscle and for the operation of the pump at a higher level during mineralocorticoid-salt hypertension. This alteration may result from increased turnover of individual sites or possibly the incorporation of more sites into the membrane as a result of mineralocorticoid-salt treatment.
Insights
Mineralocorticoid-salt hypertension increases sodium-potassium (Na-K) pump activity in vascular smooth muscle. This elevation in the Na-K pump
Area of Science:
- Cardiovascular Physiology
- Renal Physiology
- Cellular Transport Mechanisms
Background:
- Mineralocorticoid-salt hypertension is a significant risk factor for cardiovascular disease.
- The role of vascular smooth muscle ion transport in hypertension remains incompletely understood.
- The Na-K pump (sodium-potassium adenosine triphosphatase) is crucial for maintaining cellular ion homeostasis.
Purpose of the Study:
- To investigate alterations in active sodium-potassium (Na-K) transport in vascular smooth muscle during mineralocorticoid-salt hypertension.
- To determine specific parameters of Na-K transport affected by this hypertensive model.
- To elucidate the functional consequences of these transport changes in arterial smooth muscle.
Main Methods:
- Induction of mineralocorticoid-salt hypertension in rats via unilateral nephrectomy and hormone/salt administration.
- Measurement of active sodium efflux and potassium influx in isolated femoral arteries and aortas.
- Analysis of Na-K pump kinetics, including saturation, selectivity, and temperature dependence.
Main Results:
- Hypertensive rats exhibited significantly increased active sodium efflux in femoral arteries and aortas.
- This increase was attributed to enhanced maximal capacity (saturation) of the Na-K pump, not altered cell sodium concentration.
- Both active sodium efflux and potassium influx were elevated in hypertensive aortic strips, with an unchanged Na:K transport ratio.
Conclusions:
- The Na-K pump operates electrogenically in arterial smooth muscle.
- Mineralocorticoid-salt hypertension leads to an upregulated Na-K pump, likely due to increased turnover or number of transport sites.
- This enhanced pump activity may contribute to the pathophysiology of mineralocorticoid-salt-induced hypertension.