Role of histamine H3 receptor on hypoxia-reoxygenation-induced cardiac dysfunction in guinea pigs.

Hypoxia elicited a remarkable decrease in contractility and heart rate in isolated right atria from guinea pigs, a decrease which recovered partially during reoxygenation. Histamine content increased during hypoxia and decreased during reoxygenation. However, hypoxia induced a marked degranulation of mast cells. Pretreatment with alpha-methylhistamine (100-300 nM) recuperated control level contractility and heart rate, and prevented the hypoxia-reoxygenation-induced leakage of creatine phosphokinase (CPK). On the other hand, pretreatment with thioperamide (100-300 nM) decreased contractility and heart rate dose-dependently, and prevented recovery during reoxygenation. These data shows that cardiac histamine may play an important role in the protection against hypoxia-reoxygenation injury through the H3 receptor.