Induction of NO synthase 2 in ventricular cardiomyocytes incubated with a conventional bicarbonate dialysis bath

Abstract

In hypotension-prone patients, conventional bicarbonate dialysis (BD) causes a reduced cardiovascular tolerance to the treatment with respect to acetate-free biofiltration (AFB). One possible explanation is an overproduction of endogenous NO (nitric oxide) due to the residual quote of acetate (4 mM) in the BD dialysate formulation. NO overload might cause the impairment of cardiovascular reactivity observed during BD. In this study, a potential direct impact of the residual quote of acetate on the cardiac cells was investigated. Ventricular cardiac myocytes isolated from adult rat hearts were treated with three different dialysis baths with or without acetate: BD, AFB and AFB + 4 mM of acetate (AFB(+)). Corresponding levels of expression of the inducible NO synthase 2 (NOS2) were assessed after the treatments along with the measurement of single-cell action potential (AP). Incubation with acetate-containing dialysis solutions significantly enhanced (P < 0.05) the expression of NOS2 mRNA (BD: 1.11 +/- 0.31; AFB(+): 0.73 +/- 0.04, NOS2/GAPDH intensitometric ratio) with respect to the acetate-free bath (AFB: 0.03 +/- 0.01). Accordingly, protein translation was also enhanced (BD: 0.176 +/- 0.021; AFB(+): 0.135 +/- 0.009, NOS2/alpha-tubuline intensitometric ratio) with respect to AFB (0.002 +/- 0.001, P < 0.05). Measurement of the AP indicates that acetate-containing solutions determine a shortening of the repolarization phase as compared to treatment with AFB (BD: 95 +/- 13; AFB(+): 76 +/- 10; AFB: 162 +/- 16 ms). These findings show that the residual quote of acetate of the BD bath formulation affects the expression of NOS2 and the duration of AP in cardiac cells. This might cause the cardiac contractile impairment in unstable patients during BD treatment.