The fasting B6 vitamer profile and response to a pyridoxine load in normal and cirrhotic subjects

This study established the fasting plasma and urine profiles of vitamin B6 in cirrhotics and assessed the response to an oral dose of pyridoxine. High-performance liquid chromatography was used to measure all vitameric coenzymatic and degradatory forms. In 31 patients with cirrhosis and 15 healthy controls, fasting plasma and 24-hr urine collection showed: plasma pyridoxal-5'-phosphate, the biologically active form, was significantly (p less than 0.001) reduced in cirrhotics (mean +/- S.D.: 5.7 +/- 3.2 ng per ml) compared to normals (14.2 +/- 7.5 ng per ml); plasma pyridoxal was detected in more cirrhotics (48%) than normals (28%); pyridoxic acid, the end catabolite, was significantly (p less than 0.05) lower in plasma of cirrhotics compared to normals, but 24-hr urine excretion was not different. Administration of 25 mg of pyridoxine to 7 cirrhotics and 5 normals showed the following plasma changes: pyridoxine rapidly peaked at 30 min and was totally cleared from plasma by 3 hr; plasma pyridoxal and pyridoxic acid increased in parallel up to 40-fold over baseline by 1 to 2 hr and rapidly fell toward baseline by 8 hr, and plasma pyridoxal-5'-phosphate, in contrast, increased significantly (p less than 0.05) from baseline by 60 min and was maintained above normal for 24 hr. The area under the plasma concentration vs. time curve (AUC) for pyridoxal-5'-phosphate was significantly (p less than 0.05) less for the cirrhotics than normals and showed a significant negative correlation to hepatocyte function and blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)