Facilins, a novel class of biological factors that facilitate the aortic response to dopamine and other biogenic amines.

Biological fluids and tissues extracts were shown to contain biological factors, termed facilins, that facilitate the dopamine-, adrenaline-, and serotonin-mediated aortic contraction at concentrations devoid of any direct effect. Cyproheptadine and phentolamine antagonized the direct contracting effect of biogenic amines, but not the facilitated component of the aortic response thus indicating that the mechanism of action of facilins was unlike that of biogenic amines. Fresh schizophrenics' CSF displayed a stronger facilitating effect than normal CSF on the dopamine-mediated aortic response. This finding, however, was not confirmed with samples kept frozen for prolonged periods of time. Multiple molecular forms of facilins were detected in rabbit serum. Those with a high apparent molecular weight were proteinous and were neither insulin nor other factors known for their contracting effects on the aorta such as epidermal growth factor, transforming growth factor-beta, and platelet-derived growth factor.