Emotional painful stress was shown to result in a significant depression of the portal vein contractile function accompanied by its decreased adrenoreactivity and its increased dependence on changes of external temperature, calcium and glucose. Experimental myocardial infarction caused similar disturbances of the contractile function and reactivity of the portal vein. The data obtained suggested that these shifts were induced by the infarction-concomitant stress. The disturbances revealed can be prevented or limited to a considerable extent by a pretreatment of animals with alpha-adrenoblocker phentolamine, inhibitor of the lipid peroxidation antioxidant ionol, and inhibitor of lipases nicotinamide. The high efficiency of such a protection indicates that the processes blocked by these inhibitors are important links in the pathogenetic chain of stress damage to the portal vein.