Lack of a role for cardiac sympathetic nerves in the uptake and metabolism of 3H-5-hydroxytryptamine by isolated rabbit hearts.
Perfused rabbit hearts removed 3H-5-hydroxytryptamine (3H-5-HT) from a perfusion solution containing 2.6 ng/ml and a tissue-to-medium ratio of about 10 was achieved after a 55 min perfusion period. 12.4 +/- 1.0% of the cardiac total radioactivity consisted of metabolites and metabolites appeared in the venous effluent during the course of the perfusion. Pretreatment of animals with 6-hydroxydopamine reduced cardiac noradrenaline concentrations by 92%, abolished the histochemical fluorescence characteristic of noradrenaline in sympathetic nerves and abolished the mechanical response to sympathetic nerve stimulation. In these hearts, the removal of 3H-5-HT from the perfusion fluid and the accumulation of total radioactivity was normal. There was, however, a significant increase in the proportion of the total cardiac radioactivity which was present as metabolites. The results suggest that the cardiac sympathetic nerves are not the site of 3H-5-HT uptake when the concentration in the perfusion medium is low. By analogy with work in the lung, it may be the endothelial cells of the coronary microcirculation which are responsible.
D000818:Animals; D006321:Heart / Q000294:innervation*; D006892:Hydroxydopamines / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism; D010477:Perfusion; D011817:Rabbits; D012701:Serotonin / Q000378:metabolism*; D013012:Sorbitol / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000502:physiology*; D013997:Time Factors
D006892:Hydroxydopamines; D012701:Serotonin; D013012:Sorbitol; D009638:Norepinephrine