UPTAKE OF POLYAMINES BY HUMAN ENDOTHELIAL-CELLS - CHARACTERIZATION AND LACK OF EFFECT OF AGONISTS OF ENDOTHELIAL FUNCTION

Uptake of polyamines by confluent monolayers of human umbilical-vein endothelial cells (HUVECs) was found to be time-, temperature- and concentration-dependent, energy-requiring, and saturable. Kinetic constants were putrescine K(t) 3 +/- 1-mu-M, V(max). 15 +/- 7 pmol/h per mu-g of protein; spermidine, 0.7 +/- 0.2, 12 +/- 3; spermine, 1 +/- 0.7, 11 +/- 4. Putrescine uptake was inhibited by spermine or spermidine, whereas uptake of spermine or spermidine was not inhibited by 20-mu-M-putrescine. These data suggest the existence of two carriers, one shared by spermine and spermidine, and one capable of transporting all three polyamines. Pretreatment of HUVECs with thrombin ( less-than-or-equal-to 10 units/ml; 1 h), bradykinin (less-than-or-equal-to 10-mu-M; 1 h), interleukin-1 (less-than-or-equal-to 100 units/ml; 2 h) or phorbol 12-myristate 13-acetate (less-than-or-equal-to 1.0-mu-M; 1 h), all known agonists of endothelial function, had no significant effect on polyamine uptake. These responses may be of importance in angiogenesis and wound healing, and could have pharmacological significance, for there is a growing interest in the use of polyamines or polyamine analogues as therapeutic agents.