IN-VITRO PLASMA AND EUGLOBULIN CLOT LYSIS IN SUBJECTS WITH ELEVATED LIPOPROTEIN(A)

Lipoprotein(a) [Lp(a)] is assumed to have a prothrombotic role by inte rfering with the physiological functions of plasminogen due to their s tructural similarities. In order to establish if elevated plasma Lp(a) levels affect in vitro clot lysis, 12 subjects with elevated Lp(a) (3 20-1650 mg/L) and 12 subjects with normal Lp(a) (<100-141 mg/L) were s tudied. Groups were similar regarding age, gender, levels of other lip ids and fibrinolytic variables. Spontaneous lysis and lysis induced by recombinant tissue-type plasminogen activator (rt-PA) of preformed I- 125-fibrin labelled, mechanically non-compressed ('non-retracted') pla sma clots, mechanically compressed ('retracted') plasma clots and eugl obulin clots was measured. 'Non-retracted' and 'retracted' plasma clot s lysed spontaneously in 48 h on average by 15 to 16% and by 3% respec tively in both groups. In subjects with elevated Lp(a) 'non-retracted' plasma clots lysed with rt-PA (final cone. 50 and 100 ng/mL) in 4 h o n average by 34+/-4% and 58+/-6%, which was not significantly differen t from 38+/-7% and 55+/-8% clot lysis in subjects with normal Lp(a). ' Retracted' plasma clot lysed with 200 ng/mL rt-PA in 4 h on average by 32+/-5% in subjects with elevated Lp(a) and by 35+/-6% in subjects wi th normal Lp(a) (not significant, all values mean+/-SD). In subjects w ith elevated Lp(a), Lp(a) had no effect on rt-PA induced lysis of 'ret racted' plasma clots incubated in the subject's own plasma. Spontaneou s and rt-PA induced euglobulin clot lysis was not significantly differ ent between the two groups studied. The result suggested no significan t effect of plasma Lp(a) on in vitro lysis of plasma and euglobulin cl ots.