Ontogenesis of intestinal transport of 5-methyltetrahydrofolate in the rat.
Developmental aspects of the intestinal transport of 5-methyltetrahydrofolate (5-CH3H4-PteGlu) were studied in suckling (14-day-old), weanling (22-day-old), and adult (90-day-old) rats by use of the intestinal everted-sac technique. Mucosal-to-serosal transport of 0.5 microM 5-CH3H4PteGlu was linear with time for 40-min incubation and occurred at a rate of 0.035, 0.032, and 0.010 nmol X g initial tissue wet wt-1 X min-1 for suckling, weanling, and adult rats, respectively. The transport of 5-CH3H4PteGlu in all age groups was pH dependent (maximal at pH 6) and was higher in the jejunum than in the ileum. In all age groups the transport of 5-CH3H4PteGlu occurred by an active carrier-mediated system. The system was saturable; energy, temperature, and Na dependent; inhibited by structural analogues; and capable of accumulating the substrate against a concentration gradient. Kinetic parameters of the transport process, however, showed some difference. A progressive decrease in Vmax was observed from suckling to weanling to adult rats (5.1, 3.7, and 0.8 nmol X g initial tissue wet wt-1 X 30 min-1, respectively), while apparent Kt was similar (2.2, 1.73, and 1.79 microM, respectively). This study demonstrates that the transport system of 5-CH3H4PteGlu in the rat is fully developed at the suckling age. The results also suggest that the activity and/or the number, but not the affinity, of the transport carriers decrease with maturation.
D000828:Animal Population Groups / Q000254:growth & development*; D000818:Animals; D000833:Animals, Suckling / Q000254:growth & development* / Q000378:metabolism; D001692:Biological Transport; D005492:Folic Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007082:Ileum / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism*; D008727:Methotrexate / Q000494:pharmacology; D009994:Osmolar Concentration; D051381:Rats / Q000254:growth & development; D011919:Rats, Inbred Strains; D012964:Sodium / Q000494:pharmacology; D013696:Temperature; D013763:Tetrahydrofolates / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013997:Time Factors
D013763:Tetrahydrofolates; D005492:Folic Acid; D012964:Sodium; C005984:5-methyltetrahydrofolate; D008727:Methotrexate