AN INTESTINAL NATRIURETIC FACTOR

In 1975, reports were published that suggested that the gastrointestin al tract can ''taste'' the intake of sodium and in some unknown way in fluence the kidneys to increase sodium excretion. To test whether the intestine contained a natriuretic factor, intestinal tissue from cats was homogenized and fractionated by ultrafiltration to a molecular ran ge of approximately 500- 10,000 Da and separated by gel chromatography (Sephadex G25). The fractions were pooled into four large fractions t hat were assayed for ''natriuretic'' activity on anesthetized rats. Th e fraction containing the material with an apparent molecular mass of 500-1,000 Da augmented renal excretion of sodium and water, whereas th e other pooled fractions did not exhibit any consistent natriuretic ef fect. The ''natriuretic'' fractions from gel filtration were further p urified by ion exchange chromatography using a cation exchanger. The n atriuretic activity was eluted from the ion exchange chromatography co lumn at a NaCl concentration of 250 mM. Preliminary experiments on Wis tar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) suggest that the intestinal influence on renal sodium excretion is more prono unced in SHR than in WKY rats.