The effect of acute prolonged starvation on the concentrations of vitamin B6 aldehyde derivatives in whole blood

Abstract

Since plasma pyridoxal-x-5'o-phosphate (PLP) levels are used to assess vitamin B6 status low levels are frequently interpreted to indicate B6 deficiency. However plasma PLP is in a dynamic equilibrium with pyridoxal (PL) through the action of non specific alkaline phosphatases (ALP). The object of this study was to monitor possible disturbances of this equilibrium in whole blood during acute prolonged fasting (40 hrs) and the subsequent repletion period in 16 healthy male dogs. Mean plasma PLP decreased by 15 percent (p less than 0.025) and PL increased by 20 percent (p less than 0.05) at the end of the starvation period and returned to baseline values after 48 hrs of refeeding. However total plasma aldehyde (PLP and PL) B6 vitamer concentrations remained unchanged throughout the investigation period. A 35 percent increase in haemolysate PL was the only significant change (p less than 0.0005) in PLP and PL levels observed in erythrocytes during fasting. It is concluded that the use of plasma PLP alone to assess vitamin B6 status may be misleading in conditions with a disturbed plasma PLP/PL equilibrium.