Two Mechanisms of ³H-Catecholamine Accumulation in Rabbit Aorta Media Differentiated by Sensitivity to Temperature and Corticosterone

Abstract

To characterize the extraneuronal accumulation of catecholamines (CA) in the media of rabbit aorta pieces of isolated media were incubated with ³H-CA (norepinephrine, isoproterenol or normetanephrine) plus ¹⁴C-sorbitol (to estimate the extracellular space) for varying periods at 37 or 0 °C. The ³H-CA accumulation was 1.3 ml/g at 0 °C and 2.2 ml/g at 37 °C. The sorbitol space was 0.6 ml/g at both temperatures. CA accumulation at 0 and 37 °C is significantly different from each other and from sorbitol accumulation. Corticosterone and phenoxybenzamine inhibit the temperature-sensitive component of CA accumulation. Accumulation of norepinephrine at 0 ° C is unaffected by corticosterone, phenoxybenzamine or oxytetracycline. The initial rate of NE accumulation at 37 °C, from steady state accumulation at 0 °C, and the initial rate of accumulation at 0 °C were linear functions of NE concentration between 10-7 and 10-2 M. Based on differences in sensitivity to corticosterone and temperature, we conclude that CA accumulation at 0 ° C is different from the accumulation at 37 °C.