High salt alone does not influence the kinetics of the Na(+)-H+ antiporter.
During a high-salt diet, tubular sodium reabsorption is decreased. This study concerns the effect of a high-salt diet on the proximal tubular (PT) Na+ influx pathways. Brush-border membrane vesicles (BBMV) were prepared from rats on normal-salt (NS) and rats on high-salt (HS) diets. The initial uptake rates of Na+ were the same in NS and HS rats, both in the absence and the presence of 1 mM amiloride. Vmax and Km for the amiloride-sensitive Na+/H+ antiporter were also the same in the NS (Vmax 3.69 +/- 0.31 nmol mg prot-1 10 s-1, Km 6.13 +/- 0.58 mM) and HS groups (Vmax 3.54 +/- 0.28 nmol mg prot-1 10 s-1, Km 6.18 +/- 0.64 mM). There was no difference in the initial uptake rates of the Na(+)-glucose and the Na(+)-alanine symporters in NS and HS. Vmax and Km for the L-dopa-Na+ symporter were also the same in NS (Vmax 72 +/- 2.5 pmol mg prot-1 20 s-1, Km 98 +/- 14 microM) and HS groups (Vmax 78 +/- 6.0 pmol mg prot-1 20 s-1, Km 106 +/- 4 microM). In summary, HS diet does not change the kinetics of the Na+ transporters in the brush-border membrane of PT cells.
Department of Paediatrics, Karolinska Institute, St Göran's Children's Hospital, Stockholm, Sweden.
U
U
Holtbäck
A
A
Aperia
G
G
Celsi
D000584:Amiloride / Q000494:pharmacology; D026905:Amino Acid Transport Systems; D026921:Amino Acid Transport Systems, Neutral; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D002352:Carrier Proteins / Q000032:analysis / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D007687:Kidney Tubules, Proximal / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure; D007700:Kinetics; D008297:Male; D008871:Microvilli / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure; D009004:Monosaccharide Transport Proteins / Q000502:physiology; D011188:Potassium / Q000097:blood / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000097:blood / Q000493:pharmacokinetics; D012965:Sodium Chloride / Q000494:pharmacology*; D017923:Sodium-Hydrogen Exchangers; D027981:Symporters
D026905:Amino Acid Transport Systems; D026921:Amino Acid Transport Systems, Neutral; D002352:Carrier Proteins; D009004:Monosaccharide Transport Proteins; D017923:Sodium-Hydrogen Exchangers; D027981:Symporters; C052168:sodium-alanine cotransporter; D012965:Sodium Chloride; D000584:Amiloride; D012964:Sodium; D011188:Potassium