Amino acid stimulation of Na,K-ATPase activity in rat proximal tubule after high-protein diet.
Ouabain-sensitive (OS) O2 consumption was determined in proximal tubular cells from weanling rats fed 21% (normal-protein, NP) or 50% (high-protein, HP) protein diet for 4 days. Butyric acid 10(-3)M was added as a substrate for mitochondrial respiration and the ionophore amphotericin B (10 micrograms ml-1) was used to sodium-load the cells. OS respiration was higher in HP than in NP cells in both DME and amino acid-free electrolyte solution (ES). Amphotericin B significantly increased OS respiration in both NP and HP cells, implying that the Na-K pump was activated by increased intracellular Na. In cells incubated in ES, addition of amino acids stimulated OS respiration significantly in HP cells (16.9 +/- 1.4 vs 21.2 +/- 1.1 nmol min-1 mg-1 protein) and in NP cells (13.9 +/- 0.3 vs 14.9 +/- 0.6 nmol min-1 mg-1 protein). Stimulation was significantly higher in HP cells (26 +/- 4%) than in NP cells (7 +/- 4%) (P less than 0.001). The amino acids did not stimulate ouabain-insensitive respiration. The results indicate that an HP diet to weanling rats will increase proximal tubule cell Na, K-ATPase-dependent respiration by enhancing Na entry via the Na-amino acid symports.
Jakobsson
B
B
Department of Pediatrics, Huddinge Hospital, Sweden.
Larsson
S H
SH
Wieslander
A
A
Aperia
A
A
D000596:Amino Acids / Q000494:pharmacology*; D000666:Amphotericin B / Q000494:pharmacology; D000818:Animals; D004044:Dietary Proteins / Q000494:pharmacology*; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D000596:Amino Acids; D004044:Dietary Proteins; D010042:Ouabain; D000666:Amphotericin B; D000254:Sodium-Potassium-Exchanging ATPase