LIPOPROTEINS INHIBIT THE SECRETION OF TISSUE-PLASMINOGEN ACTIVATOR FROM HUMAN ENDOTHELIAL-CELLS

We studied the effect of lipoprotein(a) [Lp(a)], low-density lipoprote in (LDL), and high-density lipoprotein (HDL) on tissue plasminogen act ivator (TPA) secretion from human endothelial cells. At 1 mu mol/L, Lp (a) inhibited constitutive TPA secretion by 50% and phorbol myristate acetate- and histamine-enhanced TPA secretion by 40%. LDL and HDL also depressed TPA secretion by 45% and 35% (constitutive) and 40% to 60% (stimulated). TPA mRNA levels were also examined and found to change i n parallel with antigen secretion. In contrast to TPA, plasminogen act ivator inhibitor type-1 secretion and mRNA levels were not affected by any of the three lipoproteins. These results suggest that the interac tion of lipoproteins with certain cell-surface binding sites may inter fere with the proper production and/or secretion of TPA. (Arterioscler Thromb. 1993;14:438-442.)