Low-energy ultrasound exposure of the streptokinase molecule may enhance but also attenuate its fibrinolytic properties.

INTRODUCTION

This study explores the mechanisms of ultrasound-enhanced fibrinolysis by investigating the effects of pre-exposure to pulsed high-frequency, low-energy ultrasound on the fibrinolytic properties of streptokinase.

MATERIALS AND METHODS

Fibrinolytic activity was measured as haemoglobin release from blood clots. The fibrinolytic effects of streptokinase and ultrasound separately and in combination were studied by evaluating cumulative percentages of haemoglobin release following 1 h of exposure using two clots, one for intervention and the other concomitantly as control. In particular, the effects of exposure to ultrasound on clot-free streptokinase solution were compared to those of concomitant exposures of streptokinase solution with clot. The exposures were made at a frequency of 1 MHz (10% duty cycle) and at three intensity levels (0.5, 1.0 and 4.0 W/cm2 intensity I(SATA)).

RESULTS

Increased fibrinolysis (31.2%, P=0.028) was observed after concomitant ultrasound exposure of clot and streptokinase solution at 0.5 W/cm2 intensity. Compared to unexposed streptokinase solution, the lytic effect following exposure of streptokinase solution to ultrasound was significantly increased (32.7%, P=0.002). This enhancement effect disappeared at intensity 1 W/cm2, whilst further increase to 4.0 W/cm2 inhibited the lytic effect of streptokinase, both during concomitant exposure (-25.2%, P=0.028) and after pre-exposure of streptokinase solution to ultrasound (-25.4%, P=0.002).

CONCLUSION

The fibrinolytic property of streptokinase is modulated by exposure to pulsed ultrasound of frequency 1 MHz, being enhanced at low intensity and inhibited at high intensity.