Influence of high salt intake on the chronic blood pressure lowering effects of the baroreflex

Abstract

Prolonged electrical activation of the carotid baroreflex produces a sustained reduction in arterial pressure but whether this response is salt sensitive has not been established. To evaluate the influence of a high Na intake on the hemodynamic responses to prolonged baroreflex activation (PBA), 3 chronically instrumented dogs were maintained on normal (NS; 45 mEq/day) and high (HS; 460 mEq/day) Na intake. At each Na intake, mean arterial pressure (MAP), heart rate (HR), and Na excretion (UNaV) were monitored for 7 days before and during PBA. During NS (UNaV=40±4 mEq/day), MAP and HR were 91±3 mmHg and 73±2 bpm, respectively, before PBA. After 7 days of PBA, MAP and HR decreased 20±3 mmHg and 14±4 bpm. Subsequently, hemodynamics and Na balance were normalized by the end of a 1 week recovery period. After 7 days of HS (UNaV=446±9 mEq/day) and before PBA, MAP increased to 106 ±5 mmHg; HR was 76±1 bpm. On HS, reductions in MAP and HR were 18±6 mmHg and 12±6 bpm after 7 days of PBA, responses comparable to those seen during NS. These quantitative findings indicate that the chronic effects of PBA to lower MAP and HR are relatively unaffected by increases in Na intake above normal levels. (HL-51971).