Polyamines are absorbed through a y+ amino acid carrier in rat intestinal epithelial cells.
Due to the similarity in transport characteristics of polyamines and the y+ basic amino acid system, we hypothesized that both substrates could be moving through a common carrier site. Competitive and cross inhibition experiments in intestinal epithelial cells revealed the possibility of a common transport site. N-ethylmalemide (NEM) inhibited both lysine and putrescine transport, confirming that both were carried by a y+ transporter. Overexpressing the y+ transporter CAT-1 in a polyamine transport-deficient cell line, CHO-MG, did not reconstitute polyamine-transport. Thus, polyamines are not traveling through CAT-1. To determine if lysine is carried by a polyamine transport site, an antizyme-overexpressing cell line was used. Antizyme overexpression decreased polyamine uptake by 50%; in contrast, lysine transport was unaffected. Therefore, lysine is not traveling through a polyamine transport site. It appears that polyamines and lysine are likely traveling through a common unknown y+ transport site.
Sharpe
J G
JG
Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina 27858, USA.
Seidel
E R
ER
D000042:Absorption; D000818:Animals; D016466:CHO Cells; D027201:Cationic Amino Acid Transporter 1 / Q000378:metabolism*; D002460:Cell Line; D006224:Cricetinae; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D008239:Lysine / Q000037:antagonists & inhibitors / Q000378:metabolism; D051379:Mice; D011073:Polyamines / Q000737:chemistry / Q000378:metabolism*; D011700:Putrescine / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D013095:Spermidine / Q000037:antagonists & inhibitors / Q000378:metabolism
D027201:Cationic Amino Acid Transporter 1; D011073:Polyamines; D008239:Lysine; D005033:Ethylmaleimide; D013095:Spermidine; D011700:Putrescine