| Abstract: | Isolated and purified leucocytosis promoting factor (LPF), alternatively described as pertussis toxin, reduced the hypotension after beta 2-adrenoceptor stimulation with salbutamol as well as the negative chronotropic activity induced by the muscarinic receptor stimulant arecoline 4 days after its injection into rats. These inhibitory effects of LPF were accompanied by a reduction in basal blood pressure. No effect on autonomic responsiveness or blood pressure was observed 5 h after injection of LPF. Sublethal doses of purified B. pertussis endotoxin (LPS) elicited neither vascular beta 2-adrenergic nor cardiac cholinergic blockade 4 days following injection. Only a distinct vascular beta 2-adrenolytic effect was measured 5 h after pretreatment with the same doses of LPS. This beta 2-adrenoceptor hyporesponsiveness was accompanied by neither an anticholinergic nor a hypotensive effect, but rather by a slight but significant elevation of the blood pressure. In conclusion, both components of B. pertussis (LPS and LPF) give rise to vascular beta 2-adrenergic hyporesponsiveness irrespective of blood pressure effects. There is an important difference between both components with respect to their various kinetic profiles for this phenomenon: an early occurring and short-lasting beta 2-adrenergic blockade for LPS and a late occurring LPF-mediated beta 2-adrenergic blockade. |
