MECHANISM OF PUTRESCINE TRANSPORT IN HUMAN PULMONARY-ARTERY ENDOTHELIAL-CELLS

Effective lung repair requires optimal replication of critical cell po pulations in the lung. Endogenous polyamines such as putrescine, sperm idine and spermine play important roles in cell proliferation and diff erentiation, and may arise due to intracellular synthesis or transport into the cell. To determine the mechanism of polyamine transport in l ung endothelial cells, the uptake of putrescine in human pulmonary art ery endothelial cells was examined. Putrescine (7 nM) uptake into the cells approached equilibrium at 1 hr and was inhibited by methylglyoxa l bis(guanylhydrazone). Kinetic studies revealed that uptake occurred via both a high- and low-affinity system. The effect of several amines (700 muM) on the 15-min uptake of putrescine was examined and a rank order of inhibition was determined: methylglyoxal bis(guanylhydrazone) > putrescine > spermine > spermidine > gentamicin > mepiperphenidol. Alpha-Aminoisobutyric acid, a prototype system A amino acid, and tetra ethylammonium, an organic cation, had no effect. N-ethylmaleimide inhi bited transport 71%, whereas dinitrophenol did not. A reduction in tem perature from 37-degrees-C to 5-degrees-C resulted in a 42% decrease i n putrescine transport. Additionally, removing fetal bovine serum from the uptake medium reduced transport 38%. These data indicate that hum an pulmonary artery endothelial cells possess a specific transport sys tem for polyamines. An improved understanding of this pathway in pulmo nary endothelial cells may permit development of strategies to facilit ate growth and repair of this critical cell population.