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

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 mm ethanol was saturating for the inhibitory effect and 0.2 mm 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 mm did not decrease the ATP content of cells or the total protein content of cells which adhered to the incubation flask. Ethanol (5 mm) had no effect on the cyteine + cystine content of the cells. Intracellular pantothenate concentrations were not affected by 5 mm 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 μm 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.