Contribution of depressed reuptake to the depletion of norepinephrine from rat heart and spleen during endotoxin shock.

Norepinephrine content (microgram/g) was depressed in hearts and spleens of fasted male Holtzman rats treated intravenously with Salmonella enteritidis lipopolysaccharide (14-17 mg/kg). To investigate the mechanism of norepinephrine depletion during endotoxicosis, in vivo norepinephrine reuptake was evaluated in control and severely shocked rats using the incorporation of 3H-norepinephrine into hearts and spleens. Incorporation of 3H-norepinephrine into spleens of endotoxic rats was reduced 88%, i.e., from a control of 2309 +/- 224 dpm/gm to 270 +/- 69 dpm/gm after endotoxin. In contrast, cardiac tissue incorporation of 3H-norepinephrine was not significantly impaired, i.e., control of 11838 +/- 845 dpm/gm versus severe shock of 17783 +/- 2904 dpm/gm. In vitro analysis of total norepinephrine retained in cardiac and splenic tissue slices incubated with 3H-norepinephrine yielded results consistent with in vivo experiments: Splenic norepinephrine reuptake was significantly decreased on the order of 50% in preparations from endotoxic rats, while myocardial norepinephrine reuptake was the same in both groups. The results indicate that depression of norepinephrine reuptake is a mechanism of norepinephrine depletion in spleens but not hearts of endotoxic rats.