THE INTESTINAL-TRACT AND THE PATHOPHYSIOLOGY OF ARTERIAL-HYPERTENSION- AN EXPERIMENTAL-STUDY ON DAHL RATS

Salt depleted rabbits and humans excrete an oral sodium load more quic kly via the kidneys than an intravenous one. This has been ascribed to the presence of a sodium sensor in the gastrointestinal tract which i n some way can influence renal function. The purpose of this study was to investigate this response in the Dahl rats. Renal and faecal sodiu m excretion was followed in the two strains of rats (normotensive, sal tresistant (SR/Jr) and hypertensive, saltsensitive (SS/Jr) rats). Afte r 4 days on a low salt diet they were given NaCl (1.5 mmol kg(-1) body wt) either by gavage or intravenously. SR/Jr rats showed an increased renal sodium excretion both after oral and intravenous sodium repleti on. The excretion was 2-3 times greater after the oral than after the intravenous administration. The SS/Jr rats augmented their renal sodiu m excretion only after the oral load, although the sodium excretion wa s significantly less than in SR/Jr rats. In fact, during the first 8 h after giving sodium orally the renal excretion of sodium was on an av erage eight times larger in the SR/Jr than in the SS/Jr rats. Renal ex cretion of sodium was similar in the two strains after intravenous adm inistration. We conclude that the hypertensive SS/Jr rats have great d ifficulties in excreting an oral sodium load, a phenomenon that may be of importance in the pathophysiology of arterial hypertension in this strain of rats.