Vascular smooth muscle response to fibrinogen degradation products and 5-hydroxytryptamine: possible role in cerebral vasospasm in man.

1 Experiments were performed to determine the effects of fibrin(ogen) degradation products on the following in vitro vascular preparations: rabbit aortic strip, rat aortic strip and human basilar arterial strip. 2 Citrated plasma and streptokinase were incubated at 37 degrees C to produce a crude preparation of fibrinogen degradation products and 0.1 ml aliquots were removed at various time intervals. These samples were tested for intrinsic activity and possible interactions with EC50 and threshold concentrations of 5-hydroxytryptamine on the vascular preparations. 3 Enhancement of the responses obtained by both concentrations of 5-hydroxytryptamine was produced by samples taken throughout the streptokinase incubation period, the maximum effect being seen at 90 min. 4 The 90 min incubate produced volume-dependent (25-400 microliters) potentiations of the responses developed in the three vascular preparations to the EC50 and threshold concentrations of 5-hydroxytryptamine. 5 It is suggested that fibrin(ogen) degradation products may be involved in the intense vasoconstriction of the cerebral arteries following subarachnoid haemorrhage.