Effect of chemical anoxia on protein kinase C and Na+, K+-ATPase in hepatocytes of goldfish (Carassius auratus) and rainbow trout (Oncorhynchus mykiss)

Protein kinase C (PKC) and Na+/K+-ATPase in hepatocytes from the anoxia-tolerant goldfish (Carassius auratus) and the anoxia-intolerant rainbow trout (Oncorhynchus mykiss) were studied to determine their role in the anoxic response of these cells. PKC and Na+/K+-ATPase activities were measured for up to 90 min in the absence (normoxia) and presence (chemical anoxia) of 2 mmol l-1 sodium cyanide. PKC activity of normoxic cells from both species remained constant for the entire experimental period. Addition of cyanide had no effect on PKC activity of trout cells, which was maintained at 25 % of maximal PKC activity. In goldfish hepatocytes, PKC activity remained constant at 56 % of maximal PKC activity for 30 min but fell to 27 % after 90 min of anoxic exposure. ATPase activity was measured in hepatocytes exposed to 100 nmol l-1 phorbol-12,13-dibutyrate (PdBu), a treatment which enhanced PKC activity to its maximum level. In trout cells, there was no significant change in Na+/K+-ATPase activity whereas in goldfish hepatocytes a significant increase to about 150 % of the respective controls was observed. On the basis of the experimental evidence that in hepatocytes of goldfish (1) PKC and Na+/K+-ATPase activities decreased in parallel during chemical anoxia and (2) a stimulation of PKC activity by PdBu increased Na+/K+-ATPase activity, we postulate that PKC activity in goldfish, but not in trout, may be implicated in the Na+/K+-ATPase inhibition observed under anoxia.