The effect of ethanol and acetaldehyde on [ 14C]pantothenate incorporation into CoA in cultured rat liver parenchymal cells

Abstract

The effect of ethanol on [ 14C]pantothenate incorporation into CoA and on total CoA levels was measured in 3-day-old primary cultures of adult rat liver parenchymal cells. Ethanol decreased the incorporation of radioactivity into CoA a maximum of 67%, 5 m m ethanol was saturating for the inhibitory effect and 0.2 m m ethanol was sufficient for half-saturation. This inhibitory effect did not result from a loss of CoA precursors or from cell death. Ethanol concentrations up to 10 m m did not decrease the ATP content of cells or the total protein content of cells which adhered to the incubation flask. Ethanol (5 m m) had no effect on the cyteine + cystine content of the cells. Intracellular pantothenate concentrations were not affected by 5 m m ethanol, and increasing the pantothenate concentration did not affect ethanol inhibition. Ethanol inhibition of [ 14C]pantothenate conversion to CoA could be fully reversed by rinsing the cells free of ethanol. The ethanol inhibition could also be fully reversed by addition of 4-methylpyrazole, indicating that ethanol must be oxidized via alcohol dehydrogenase to exert its inhibitory effect. Acetaldehyde, the immediate product of alcohol dehydrogenase, was also an inhibitor of the incorporation of [ 14C]pantothenate into CoA; the maximum inhibition was 63%. Acetaldehyde concentrations maintained between 18 and 103 μ m inhibited incorporation by 57%. The inhibition by acetaldehyde did not correlate well with changes in the NADH and NAD + ratio of the cells (as determined by measuring changes in the lactate-to-pyruvate ratio). The ability of glucagon, dibutyryl cAMP + theophylline, or dexamethasone to stimulate [ 14C]pantothenate conversion to CoA was not decreased by the addition of ethanol or acetaldehyde, indicating that ethanol inhibition does not occur by reversal of the cAMP-mediated regulatory mechanism for CoA biosynthesis.