Putrescine uptake by rabbit intestinal brush-border membrane vesicles.
The transport of putrescine in rabbit intestinal brush-border membrane vesicles is a time-dependent, Na+ and H+ gradient-independent slow process, reaching a high equilibrium level from 1 hr onwards. An approximately 12-fold concentration gradient of 5.4 microM putrescine was generated in the vesicles after 3 h of incubation at 25 degrees C, suggesting a substantial binding of the polyamine to membrane components. Putrescine uptake did not appear to occur via a polyamine-H+ exchange pathway, but the activity of transport was strongly reduced when the medium pH was lowered from 7.5 to 6.0. Although it was inhibited in the presence of SCN-, putrescine uptake was found neither to involve a preferred anion nor to be sensitive to changes in the membrane potential. Putrescine accumulation was substantially stimulated in the presence of a 10 mM concentration of the divalent cations Ca2+, Mg2+ or Ba2+, unlike the monovalent cations K+, Na+ or Li+. Despite the presence of a Ca(2+)-dependent transglutaminase activity, vesicular accumulation does not appear to result from covalent binding of putrescine to membrane peptides. Inhibition of the uptake by polyamines, unlike choline and dibasic amino acids, shows that putrescine may bind noncovalently to other specific anionic sites.
Brachet
P
P
Unité de Nutrition Humaine et Physiologie Intestinale de l'I.N.R.A., Faculté des Sciences Pharmaceutiques et Biologiques, Paris, France.
Tomé
D
D
D000818:Animals; D000838:Anions / Q000494:pharmacology; D002413:Cations, Divalent / Q000494:pharmacology; D002414:Cations, Monovalent / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007408:Intestinal Absorption / Q000187:drug effects; D007413:Intestinal Mucosa / Q000378:metabolism / Q000648:ultrastructure*; D008297:Male; D008871:Microvilli / Q000378:metabolism; D011700:Putrescine / Q000493:pharmacokinetics*; D011817:Rabbits; D013861:Thiocyanates / Q000494:pharmacology
D000838:Anions; D002413:Cations, Divalent; D002414:Cations, Monovalent; D013861:Thiocyanates; C024553:sodium thiocyanate; D011700:Putrescine