Cytosolic free calcium elevation in vascular smooth muscle cells induced by cerebrospinal fluid from patients with subarachnoid hemorrhage--biochemical nature of the calcium-mobilizing factor.

The present study was undertaken to characterize the biochemical nature of the factor in cerebrospinal fluid (CSF) from patients with subarachnoid hemorrhage (SAH) that induces a transient elevation of cytosolic free calcium in cultured vascular smooth muscle cells. Cell-free CSF collected from patients on days 7-10 after SAH was treated in three different ways: heating, ultrafiltration, and salting out with ammonium sulfate. The effects of the resultant solutions on the level of cytosolic free calcium in cultured vascular smooth muscle cells were then examined. Heated CSF and ultrafiltrated solution containing substances with molecular weights of less than 10,000 caused no significant elevation of cytosolic free calcium. Proteins precipitated by 50-75% saturated ammonium sulfate caused an increase in the level of cytosolic free calcium and also produced a rapid accumulation of inositol 1,4,5-trisphosphate in vascular smooth muscle cells. The results indicate that the factor responsible for the increase in cytosolic free calcium in cultured vascular smooth muscle cells is a protein with a molecular weight of more than 10,000, and the factor stimulates receptor-mediated phosphoinositide breakdown.