The rate constants for the efflux of deaminated metabolites of 3H-dopamine from the perfused rat heart.

Hearts of rats pretreated with reserpine and FLA 63 were perfused for 30 min with 1 mumol/l 3H-dopamine and in the presence of an inhibitor of either neuronal (30 mumol/l cocaine) or extraneuronal uptake (87 mumol/l corticosterone). From the rate at which the deaminated metabolites appeared in the venous perfusate and from the tissue content of the metabolites at the end of the perfusion rate constants for efflux (k-values) were determined. The k-values for the deaminated metabolites of dopamine did not differ when the deamination of dopamine was restricted to either extraneuronal or neuronal sites. However, marked differences existed between the rate constant for efflux of the deaminated acid DOPAC (dihydroxyphenyl-acetic acid) and the glycol DOPET (dihydroxyphenyl-ethanol). The relationship between the apparent lipophilicity and the rate constant for efflux of DOPAC fitted very well with that reported for other metabolites of catecholamines.