Pantothenic Acid Uptake and Metabolism by Red Blood Cells of Rats

Abstract

Red blood cells (RBC) of rats and humans contain pantothenic acid (PA) derivatives, generally referred to as bound PA, which were never characterized or quantitated. This study was undertaken to define those factors that determine the rates of uptake and efflux of PA, and possibly PA derivatives, in RBC. Uptake of PA by RBC was studied by incubating RBC with different concentrations of PA (0.34–34.0 µmol/L), each containing [14C]PA (0.34 µmol/L) at 37°C for 3–360 min. The effects of Na+, energy and pH on the uptake of PA in RBC were determined in experiments varying media concentrations of Na+ (0–152 mmol/L), glucose (0 and 10 mmol/L) or pH (7.2–7.6). The release of PA from RBC was studied by incubating RBC containing [14C]PA (0.10–10.4 nmol/107 RBC, final concentration) in fresh media at 37°C for 10–240 min. Uptake and efflux of PA were found to be nonsaturable; uptake was not affected by Na+, energy or pH. Quantitative and qualitative determination of PA derivatives was by enzymatic hydrolysis of lysed RBC, followed by analysis of PA by RIA and paper chromatography. The RBC were found to contain PA, 4′-phosphopantothenic acid and pantetheine. We conclude that PA diffuses passively into and out of RBC and that RBC contain only PA, 4′-phosphopantothenic acid, pantetheine and no CoA.