Sodium balance and jejunal ion and water absorption in Dahl salt-sensitive and salt-resistant rats.

Abstract

1. Apparent Na+ absorption and jejunal water, Na+, Cl- and K+ absorption in vivo was evaluated in young (prepubertal) and adult Dahl salt-sensitive (DS) and Dahl salt-resistant (DR) rats kept on a low-salt (low-salt rat chow + distilled water) or a high-salt diet (HS1 diet: NaCl-enriched rat chow + distilled water; HS2 diet: standard rat chow + 1% saline as drinking fluid). These two high-salt diets were chosen because the HS1 regimen has been shown to increase blood pressure (BP) in DS rats and the HS2 regimen decreases jejunal water and ion absorption in normotensive Wistar rats. 2. The HS1 or HS2 diet increased BP in young and adult DS rats but had no effect on the BP of young and adult DR rats. 3. Irrespective of dietary Na+ intake, no significant difference of apparent Na+ absorption (dietary Na+ intake minus faecal Na+ output) was observed between DS and DR rats both in prepuberty and in adulthood. Young DS rats kept on a low-salt diet had increased faecal Na+ output in comparison with young DR rats. This difference disappeared with increasing dietary Na+ intake. 4. There were no interstrain differences on the effect of a high-salt diet on jejunal Na+ and K+ absorption in young and adult DS and DR rats. However, high-salt diets stimulated jejunal water and Cl- absorption in young DS rats, but not in adult DS rats and young and adult DR rats. Interstrain differences of water and Cl- absorption were observed only in adulthood. Adult DR rats kept on an HS2 diet absorbed more water and Cl- than their DS counterparts. 5. Our results do not indicate any abnormalities of apparent Na+ absorption and jejunal water and electrolyte transport in DS and DR rats. We conclude that there is no relationship between intestinal Na+ absorption and sensitivity or resistance to induction of experimental salt hypertension.