[Metabolic balances of sodium and water in young spontaneously hypertensive rats and the effects of chronic inhibition of the conversion enzyme].

In order to show in SHR to what extent the kidneys excrete salt and water in proper relation to intake and whether antihypertensive action of converting enzyme inhibition (CEI) involves changes in salt--and water--balance, metabolic studies were conducted during 12 weeks following weaning (wk 4 to 15) on 4 groups of 9 male rats: SHR, WKY and SHR.C, WKY.C (C: given 30 mg captopril/kg body wt every 12 hr by gavage), all fed a standard rat chow (sodium 104 +/- 3 meq/g) in metabolic cages with free access to distilled water. SHR exhibited a higher weekly sodium retention than WKY only up to the end of wk 9 (5.2 +/- 0.5 vs 3.4 +/- 0.6 mEq/wk, p less than 0.001). This was due to lower urinary excretion and greater intakes since fecal losses were higher. From ages 10 through 15 wk, weekly sodium retention was the same in both strains although urinary sodium excretion in SHR was still significantly lower. SHR also retained more water at 7 and 8 wk than age-matched WKY due to lower urinary excretion. From ages 4 to 15 wk, SHR exhibited a reduced relationship of urinary sodium and water excretion to systolic arterial pressure. From ages 4 to 15 wk, weekly sodium retention in SHR.C (2.9 +/- 0.9 mEq/wk) was below that in SHR (4.5 +/- 0.9 mEq/wk, p less than 0.05) and not different from that in WKY (3.7 +/- 0.8 mEq/wk). As intakes and fecal losses were unchanged by CEI, this was due to increased urinary sodium excretion in SHR.C over that in SHR (by 1.4 +/- 0.5 mEq/wk.(ABSTRACT TRUNCATED AT 250 WORDS)