Renal acid excretion and intracellular pH in salt-sensitive genetic hypertension.
Acid-base status and renal acid excretion were studied in the Dahl/Rapp salt-sensitive (S) rat and its genetically salt-resistant counterpart (R). S rats developed hypertension while on a very high salt diet (8%) and while on a more physiological salt diet (1%) and remained normotensive while on a very low salt diet (0.08%). Under the high salt diet, intracellular pH measured in freshly isolated thymic lymphocytes using 2',7'-bis (carboxyethyl)-5 (6)-carboxyfluorescein acetomethyl ester, a pH-sensitive dye, was lower in S than in R rats both when measured in the presence of HCO3/CO2 (7.32 +/- 0.02 vs. 7.38 +/- 0.02, respectively, P < 0.05) and in its absence (7.18 +/- 0.04 vs. 7.27 +/- 0.02, respectively, P < 0.05). Under the high salt diet, net acid excretion was higher in S than R rats (1,777 +/- 111 vs. 1,017 +/- 73 muEq/24 h per 100 g body wt, respectively, P < 0.001), and this difference was due to higher rates of both titratable acid and ammonium excretion. Directionally similar differences in intracellular pH and net acid excretion between S and R rats were also observed in salt-restricted animals. In S and R rats placed on a normal salt intake (1%) and strictly pair-fed to control food intake as a determinant of dietary acid, net acid excretion was also higher in S than in R rats (562 +/- 27 vs. 329 +/- 21 muEq/24 h per 100 g, respectively, P < 0.01). No significant difference in either blood pH or bicarbonate levels were found between S and R rats on either the 0.08%, 1%, or 8% salt diets. We conclude that renal acid excretion is augmented in the salt-sensitive Dahl/Rapp rat. Enhanced renal acid excretion may be a marker of increased acid production by cells from subjects with salt-sensitive hypertension.
Batlle
D C
DC
Department of Medicine, Northwestern University Medical School, Chicago, Illinois 60611-3008.
Sharma
A M
AM
Alsheikha
M W
MW
Sobrero
M
M
Saleh
A
A
Gutterman
C
C
D000818:Animals; D001794:Blood Pressure; D001835:Body Weight; D004573:Electrolytes / Q000097:blood; D005919:Glomerular Filtration Rate; D006863:Hydrogen-Ion Concentration; D006973:Hypertension / Q000097:blood / Q000235:genetics / Q000503:physiopathology*; D007668:Kidney / Q000502:physiology / Q000503:physiopathology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012982:Sodium, Dietary
D004573:Electrolytes; D012982:Sodium, Dietary