Summary
The activity drop of 5 u streptokinase was measured in 1 ml each of various solutions
(0.9% NaCl solution, 5% glucose solution, 5% levulose solution, 10% dextran solution,
gelatin solution, 3% albumin solution, Michaelis buffer, glucose (5%)-heparin (750
u/ml) solution) at different incubation temperatures (–20° c, 4° c, 20 c, 37 C), and
over different observation periods (15 min, 30 min, 45 min, 60 min, 6 h, 12 h, 24
h, and 48 h). Solution media tested for streptokinase-protecting quality were broken
down into three groups.
Group I: Solvents displaying excellent stabilizing properties (gelatin and albumin
solutions).
Group II: Solvents displaying medium stabilizing properties (dextran and levulose
solutions).
Group III: Solvents displaying poor stabilizing properties (NaCl and glucose solutions,
Michaelis buffer).
In testing streptokinase concentrations as used for therapeutic purposes (1500 u/ml,
50,000 u/ml), no decay was found to take place over observation periods of up to 48
h, and no influence by different solvents (Group I, II or III) was traceable. Heparin
stored with streptokinase at room temperature over a period of 48 h did not alter
the streptokinase stability.
Some mechanisms concerning the stability pattern of streptokinase are discussed. It
appears that low streptokinase concentrations need negatively charged colloids to
keep the protein structure intact. The streptokinase-protecting macro-molecules tested
so far were albumin, gelatin, and streptokinase. Obviously, streptokinase by itself
was able to preserve its own stability provided its concentration was of a certain
order of magnitude (1500 u/ml, 50,000 u/ml).
