Abstract

Norepinephrine (NE) was released from perfused cat spleens either by nerve stimulation or injection of potassium in phenoxybenzamine-treated animals. Krebs-bicarbonate solution was perfused at a rate of about 7 ml/min at 35°C. Spontaneous release of NE was increased when spleens were perfused with nitrogenated glucose-free Krebs' solution. Similarly, treatment with dinitrophenol with glucose deprivation also resulted in increased spontaneous release. Ouabain also increased it. Sulihydryl group inhibitors, iodoacetic acid (5 x 10^-4 M), p-chloromercuribenzoate (10^-4 M) and N-ethylmaleimide (5 x 10^-4 M), markedly and irreversibly blocked release evoked both by nerve stimulation and potassium. Glucose deprivation or treatment with 2-deoxy-glucose (11 or 33 x 10^-3 M) did not affect release. Anoxia, dinitrophenol (5 x 10^-4 M) and cyanide (5 x 10^-3 M) appeared to slightly enhance the release, at least initially, in response to nerve stimulation and potassium injection. Anoxia in absence of glucose for over two hours markedly inhibited release due to nerve stimulation or potassium. Dinitrophenol or cyanide in absence of glucose produced similar inhibition. The inhibition was irreversible. Perfusing the spleen with Krebs' solution at low temperature (15-17°C) also reduced NE release. Ouabain (10^-4 M) initially enhanced the release due to potassium but later on depressed it. NE levels of splenic slices exposed to N₂, dinitrophenol (5 x 1O^-4 M) or cold for two hours did not change. Exposure to N₂ + glucose-free Krebs' solution lowered it by 66%. Treatment with dinitrophenol (5 x 10^-4 M) + glucose-free Krebs' reduced the levels by 90%. It is concluded that the energy requirements for the release of NE are not extensive and that release is not impaired in the absence of either oxidative or glycolytic metabolism.