Retention of 14C label is lower in old than in young Wistar rats after oral dosing with [14C]pyridoxine.
Ten young (6-mo-old) and ten old (31-mo-old) male Wistar rats fed a purified diet (250 g casein and 6 mg pyridoxine.HCl per kg) from weaning were given either a single oral dose or five repeated oral doses of 14C-labeled pyridoxine. At various times after dosing animals of each age group were killed. Absorption of orally dosed [14C]pyridoxine.HCl was not found to be different between young and old rats. Total body retention of 14C label administered was modestly but significantly lower in old than in young rats. However, distribution of 14C label over various tissues and among the various B-6 vitamers was similar. No significant age-related differences were observed in the biokinetic parameters derived from urinary excretion data. Contrary to the findings for 14C label distribution, age-related differences were observed for absolute level of tissue 14C-labeled vitamers. The lower [14C]pyridoxal-5'-phosphate content in liver and muscle, and [14C]pyridoxamine-5'-phosphate content in liver, of old animals indicated an age-related difference in liver and muscle vitamin B-6 disposition. In both young and old rats, and in both liver and muscle tissue, pyridoxamine-5'-phosphate was observed to be a faster-exchanging tissue vitamin B-6 pool than pyridoxal-5'-phosphate.
Bode
W
W
TNO-CIVO Toxicology and Nutrition Institute Zeist, Department of Nutrition, The Netherlands.
Mocking
J A
JA
van den Berg
H
H
D000284:Administration, Oral; D000375:Aging / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D001835:Body Weight; D002250:Carbon Radioisotopes; D007408:Intestinal Absorption; D008297:Male; D009929:Organ Size; D011736:Pyridoxine / Q000378:metabolism / Q000493:pharmacokinetics*; D051381:Rats; D011919:Rats, Inbred Strains; D014018:Tissue Distribution
D002250:Carbon Radioisotopes; D011736:Pyridoxine