Recent studies have shown that the bicarbonate reabsorptive capacity ofthe proximal tubule is increased in metabolic acidosis. For net bicarbonate reabsorption &o be regulated, there may be changes in the rate of apical H+ secretion as well as in the basolateral base exit step. The present studies examined the rate of Na+/H+ exchange (acridine orange method) and Na+/HCO3 cotransport (22Na uptake) in apical and basolateral membranes prepared from the rabbit renal cortex by sucrose density gradient centrifugation. NH4C loading was used to produce acidosis (arterial pH, 7.27±0.03), and Cl-deficient diet with furosemide was used to produce alialosis (arterial pH, 7.51±0.02). Maximal transport rate (V..) of Na+/H' antiporter and Na+/HCO3 cotransporter were inversely related with plasma bicarbonate concentration from 6 to 39 mM. Furthermore, the maximal transport rates of both systems varied in parallel; when V. for the Na+/ HCO3 cotransporter was plotted against V,,x for the Na+/H+ antiporter for each of the 24 groups of rabbits, the regression coefficient (r) was 0.648 (P < 0.001). There was no effect of acidosis or alkalosis on affinity for Na+ of either transporter. We conclude that both apical and basolateral H+/HCO3 transporters adapt during acid-base disturbances, and that the maximal transport rates of both systems vary in parallel during such acid-base perturbations.

In obese children and adolescents, IR is associated with elevated levels of IL-6 and diminished values of sIL-6R.

No abstract

Rhabdomyolysis is an uncommon complication associated with 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors. We observed six cases of cerivastatin-associated rhabdomyolysis: two patients developed acute renal failure requiring hemodialysis, and one patient died. Four of the patients had impaired renal function, and five were prescribed drugs with the potential to interact with cerivastatin. Also, five of the six patients presented with symptoms of rhabdomyolysis 3-4 weeks after starting cerivastatin therapy.

N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) is a carboxyl-activating agent and has been shown to inhibit the renal Na+/H+ antiporter. The purposes of the present studies were to characterize the kinetics of inhibition of the Na+/H+ antiporter by EEDQ and to determine whether amiloride analogues affect the ability of EEDQ to inhibit the rate of Na+/H+ exchange. Brush-border membrane vesicles (BBMV) were prepared from rabbit kidneys; Na+/H+ exchange rate was assessed by the fluorescence quenching of acridine orange. EEDQ produced a concentration-dependent inhibition of Na+/H+ exchange; the effect was to decrease the maximum activity (Vmax) from 5.51 to 2.03 fluorescence units X mg protein-1 X S-1) and Km (from 14.1 to 8.7 mM) compared with control BBMV. Pretreatment of BBMV with amiloride before the addition of EEDQ maintained both Vmax and Km at values that were not significantly different from those for control BBMV. Compared with a series of analogues, amiloride was only the third most potent inhibitor of the rabbit renal Na+/H+ antiporter; amiloride, however, provided the greatest protection against inhibition of the antiporter by the subsequent addition of EEDQ. These findings suggest that the 2-carbonylguanidininum moiety and 6-chloro atom are important for binding of amiloride to sites at or near the antiporter; the group at position 5 is important in determining the ability of amiloride to protect against inhibition of the Na+/H+ antiporter by EEDQ. Finally, the ability of amiloride to protect against inactivation of the renal Na+/H+ antiporter by EEDQ is reversible.