THE ROLE OF HEMOLYSATE IN THE FACILITATION OF OXYHEMOGLOBIN-INDUCED CONTRACTION IN RABBIT BASILAR ARTERIES

The importance of factors within hemolysate in modulating oxyhemoglobi n (oxyHb)-induced contraction was examined in an in vitro model of rab bit basilar arteries. When the basilar arteries were exposed to purifi ed oxyHb alone, the contractile response observed was significantly we aker than that seen in arteries exposed to hemolysate containing an eq ual concentration of oxyHb. In order to delineate the nature of the fa ctors within hemolysate that facilitate contraction, hemolysate was fr actionated, and various components were tested individually for their ability to elicit this effect. A low-molecular-weight fraction of hemo lysate, ranging from 0.5 to 2.0 kD, elicited only a mild contraction. However, when this fraction was combined with purified oxyHb, the cont ractile response was comparable in magnitude to that of unfractionated hemolysate. These studies confirm that purified oxyHb is capable of i nducing contraction in vitro. The data also demonstrate that oxyHb eli cits a significantly weaker contraction than does hemolysate. In addit ion, the results suggest that low-molecular-weight components in hemol ysate (in the 0.5- to 2.0-kD range), while incapable of inducing a pot ent contraction alone, may act in concert with oxyHb to elicit the vas oconstriction seen following subarachnoid hemorrhage.