Hemodynamic and metabolic evidence of salt sensitivity in spontaneously hypertensive rats

Hemodynamic and Metabolic evidence of salt sensitivity in spontaneously hypertensive rats. Sixteen female Wistar Kyoto (WKY) and 16 female spontaneously hypertensive rats (SHR) were studied hemodynamically and metabolically after prolonged (3 months) high sodium intake. Eight rats of each strain were given tap water to drink and served as controls, and another eight rats of each strain received 1% sodium chloride in tap water. Hemodynamic and metabolic evaluation disclosed that high salt intake by the WKY rats increased their cardiac index, oxygen consumption, and urinary sodium excretion; decreased body weight, total peripheral resistance index, oxygen extraction, and plasma renin activity; and had no effect upon mean arterial pressure, heart rate, fluid intake, urine volume, and potassium excretion. In contrast, high salt intake by the SHR increased their mean arterial pressure, total peripheral resistance index, fluid intake, urinary volume and sodium excretion; decreased plasma renin activity; and had no effect upon heart rate, cardiac index, and urinary potassium excretion. Salt-treated SHR rats had significantly higher fluid intake than their WKY counterparts had. The elevated arterial pressure and peripheral vascular resistance demonstrate an increased sensitivity to dietary salt in SHR but not in corresponding WKY controls. The further elevation of arterial pressure by salt in the SHR was due mainly to a further increase in vascular resistance. Preuves hemodynamique et metabolique de la sensibilite au sel chez les rats spontanement hypertendus. Seize rattes Wistar Kyoto (WKY) et 16 rattes spontanement hypertendues (SHR) ont ete etudiees des points de vue hemodynamique et metabolique apres un apport eleve de sodium maintenu pendant 3 mois. Huit rats dans chaque groupe WKY et SHR ont eu de l'eau du robinet et ont servi de controle alors que les autres avaient du 1% sodium chloride dans l'eau du robinet. L'etude hemodynamique et metabolique a montre que chez les animaux WKY soumis a l'apport eleve de sodium l'index cardiaque, la consommation d'oxygene et l'excretion urinaire de sodium augmentent alors que le poids corporel, l'index de resistance peripherique totale, l'extraction d'oxygene et l'activite renine plasmatique diminuent. Il n'y a pas d'effet sur la pression arterielle moyenne, la frequence cardiaque, l'ingestion de liquide, le debit urinaire et la kaliurese. Au contraire, l'apport de sodium eleve chez SHR augmente la pression arterielle moyenne, l'index de resistance peripherique totale, l'ingestion de liquide, le debit urinaire et l'excretion de sodium. Il diminue l'activite renine plasmatique et n'a pas d'effet sur l'index cardiaque et la kaliurese. Les SHR soumis au sel ont une ingestion de liquide significativement superieure a celle de leurs homologues WKY. La pression arterielle et la resistance peripherique elevees demontrent l'augmentation de la sensibilite au sodium alimentaire chez SHR mais non chez les controles WKY. L'elevation supplementaire de la pression arterielle par le sel chez SHR est due essentiellement a un accroissement supplementaire des resistances vasculaires.