Effect of drugs on turnover rate of heart norepinephrine

The effect of various drugs on the turnover rate of heart NE was determined from the product of the endogenous NE concentration and of the rate constant of NE-H³ declinc after injection of the radioactive amine in tracer doses. Chlorisondaminc, pcmpidinc. BW 392060, pargyline, and DMI inhibited the decline of NE-H³ and reduced the turnover rate by 30–50%. Only pargylinc and BW 392060 elicited detectable changes in the NE level. It is proposed that by decreasing the efflux of neurohormonc these drugs produce a slight rise in intrancuronal NE which leads to an inhibition of synthesis. The data support the concept that an autorcgulatory mechanism maintains the constancy of NE levels in the heart.