ENHANCEMENT OF HISTAMINE-INDUCED VASCULAR LEAKAGE BY PERTUSSIS TOXIN IN SJL J MICE BUT NOT BALB/C MICE/

Pertussis toxin (PTX) from Bordetella pertussis is known to enhance in flammatory responses which involve histamine and serotonin, including cell-mediated delayed-type hypersensitivity reactions. In this study w e examined the effects of PTX on histamine-modulated microvascular res ponses. The actions of histamine on arteriole diameter and post-capill ary leaky site formation in the cremaster muscle were measured intra-v itally in two inbred strains of mice (viz. BALB/c and SLJ). In SJL mic e the rate and extent of histamine-induced leaky site formation were g reatly enhanced (from 8.3 to 21.0 leaky sites per 0.1 cm2) by pre-expo sure to PTX. In sharp contrast, PTX did not alter histamine-induced le aky site formation in BALB/c mice. Histamine-mediated dilation in arte rioles in both strains of mice were not enhanced by PTX. PTX may enhan ce the development of inflammatory responses by enhancing histamine-in duced leaky site formation of the microvasculature.