Lack of hormonal stimulation of pyridoxine metabolism in isolated rat hepatocytes.
Isolated hepatocytes obtained from Sprague-Dawley rats (145-175 g) were incubated for 15 min at 30 degrees C in Krebs-Henseleit bicarbonate buffer, pH 7.4, containing 0.5 mM concentration of each of the 20 natural amino acids and either 4.5 or 23 microM [U-14C]pyridoxine. Pyridoxine, pyridoxal, pyridoxal phosphate, and pyridoxic acid separated by an anion-exchange chromatographic technique were quantified using a phosphate analyzer and a liquid scintillation counter. The conversion of [U-14C]pyridoxine to its metabolites was more than doubled by increasing the amount of pyridoxine (4.5 to 23 microM) in the incubation medium. Insulin (10 mU/ml), glucagon (1 nM), or epinephrine (10 microM) did not have any significant effect on the conversion of [14C]-pyridoxine to pyridoxal, pyridoxal phosphate, or pyridoxic acid. Our earlier observations of a large decrease in serum pyridoxal phosphate in the diabetic rat cannot be explained by any direct hormonal effects on pyridoxine metabolism.
Rogers
K S
KS
Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907.
Mohan
C
C
Geiger
P J
PJ
Memon
R A
RA
Bessman
S P
SP
D000818:Animals; D002250:Carbon Radioisotopes; D002478:Cells, Cultured; D004837:Epinephrine / Q000494:pharmacology*; D005934:Glucagon / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D011336:Probability; D011730:Pyridoxal / Q000378:metabolism; D011732:Pyridoxal Phosphate / Q000378:metabolism; D011735:Pyridoxic Acid / Q000378:metabolism; D011736:Pyridoxine / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D002250:Carbon Radioisotopes; D007328:Insulin; D011730:Pyridoxal; D011735:Pyridoxic Acid; D011732:Pyridoxal Phosphate; D005934:Glucagon; D011736:Pyridoxine; D004837:Epinephrine