HIGH-SALT ALONE DOES NOT INFLUENCE THE KINETICS OF THE NA-H+ ANTIPORTER()

During a high-salt diet, tubular sodium reabsorption is decreased. Thi s study concerns the effect of a high-salt diet on the proximal tubula r (PT) Na+ influx pathways. Brush-border membrane vesicles (BBMV) were prepared from rats on normal-salt (NS) and rats on high-salt (HS) die ts. The initial uptake rates of Na+ were the same in NS and HS rats, b oth in the absence and the presence of 1 mm amiloride. V(max) and K(m) for the amiloride-sensitive Na+/H+ antiporter were also the same in t he NS (V(max) 3.69 +/- 0.31 nmol mg prot-1 10 s-1, K(m) 6.13 +/- 0.58 mm) and HS groups (V(max) 3.54 +/- 0.28 nmol mg prot-1 10 s-1 K(m) 6.1 8 +/- 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. V(max) a nd K(m) for the L-dopa-Na+ symporter were also the same in NS (V(max) 72 +/- 2.5 pmol mg prot 120 s-1, K(m) 98 +/- 14 mum) and HS groups (V( max) 78 +/- 6.0 pmol mg prot-1 20 s-1, K(m) 106 +/- 4 mum). In summary , HS diet does not change the kinetics of the Na+ transporters in the brush-border membrane of PT cells.