The response to water-salt loading: sodium metabolism in spontaneously hypertensive rats.

The natriuretic response to loading with Ringer solution or 2% NaCl solution (5% of b.w.) was exaggerated in conscious rats with spontaneous hypertension (SHR) as compared to normotensive Wistar Kyoto rats (WKR). The content of bound sodium in the extracellular fraction was found to be increased in SHR as compared to WKR. The changes in the kinetics of sodium exchange were similar to those observed in Wistar rats maintained on a high sodium diet. The accumulation of sodium in the extracellular bound fraction and its saturation of the tissue pools may be involved in the development of the exaggerated natriuretic response to acute sodium loading produced in SHR.