Catecholamine synthesis requires O2. Crucian carp (Carassius carassius L.), which are extremely anoxia tolerant, were exposed to anoxia for 76 or 160 h. The brain levels of dopamine and norepinephrine (no epinephrine was found in brain) remained relatively constant even after nearly 1 wk of anoxia, indicating very well-functioning transmitter reuptake mechanisms and/or the absence of O2-independent degradation. In contrast, in the kidney (which contains chromaffin tissue), the catecholamine content (at least norepinephrine) decreased by 22-60% after 160 h of anoxia. Moreover, when anoxic crucian carps were put in normoxic water for approximately 40 min, the kidney catecholamine levels increased by 50-370%, whereas no significant effect was seen in brain. Thus, in the kidney, all that was lost during nearly 1 wk of anoxia seemed to be regained in less than 40 min of normoxia. This might reflect an adaptive strategy. Because of the limited possibility of recovering catecholamines that have been released into the bloodstream, the crucian carp chromaffin tissue might have become very good at taking the opportunities given by short contacts with O2 to rapidly renew its catecholamine store.
Secreting Tumors of Chromaffin Tissue