Mechanism of hemolysate-induced [Ca²⁺]_i elevation in cultured fibroblasts

Abstract

Erythrocyte lysate (hemolysate) released from blood clot after subarachnoid hemorrhage is the causative agent for chronic cerebral vasospasm, a prolonged contraction of cerebral arteries. Fibroblasts, the outer layer cells of vessel wall that in contact with blood clot directly, may contribute to cerebral vasospasm. However, the effect of hemolysate on intracellular Ca^{2 +} ([Ca^{2 +}]_i) mobilization in fibroblasts has not been studied. We investigated hemolysate-induced [Ca^{2 +}]_i mobilization in cultured neonatal human dermal and canine middle cerebral arterial fibroblasts by using fura-2 microfluorimetry. Hemolysate increased [Ca^{2 +}]_i by releasing internal Ca^{2 +} stores and promoting Ca^{2 +} entry. Tyrosine kinase inhibitors partially but significantly reduced the effect of hemolysate. The major components of hemolysate, oxyhemoglobin (OxyHb) and adenosine triphosphate (ATP) failed to mimic the effect of hemolysate. In cultured canine middle cerebral arterial fibroblasts, hemolysate produced similar Ca^{2 +} mobilization to that of dermal cells. OxyHb and ATP failed again to reproduce the effect of hemolysate. We conclude that hemolysate increases [Ca^{2 +}]_i in fibroblasts and this effect of hemolysate is not mediated by OxyHb or ATP but by some unknown factors.