Lb. Weekley et P. Eyre, ALTERED ENDOTHELIUM-DEPENDENT ALPHA-ADRENERGIC VASCULAR REACTIVITY FOLLOWING EXPOSURE TO PASTEURELLA-HAEMOLYTICA ANTIGENS, Veterinary research communications, 18(2), 1994, pp. 133-140
Rats were injected with sterile saline (controls), 10(5) cfu of Pasteu
rella haemolytica (biotype A) obtained from a commercial vaccine, or a
commercial Pasteurella leukotoxoid vaccine. Three days after vaccinat
ion, the animals were killed and the thoracic aorta was removed. In so
me experiments the vascular endothelium was mechanically removed. Each
isolated aorta was placed in a tissue bath and the biophysical respon
ses to methoxamine (alpha-1 agonist) were determined. In separate expe
riments the endothelial surface was examined by scanning electron micr
oscopy. In endothelium-intact vessels both vaccines appeared to enhanc
e the contractile response to methoxamine. On the other hand, in endot
helial-denuded vessels, the methoxamine-mediated contractile response
was enhanced in the P. haemolytica-treated group but not in animals va
ccinated with leukotoxoid. Furthermore, scanning electron microscopy r
evealed deposition of a fibrin-like material on the endothelial surfac
e of vaccinated animals. These results suggest that exposure to vaccin
e-derived P. haemolytica antigens alters the morphology and adrenergic
responsiveness of vascular smooth muscle.