Octopine metabolism in Sepia officinalis: effect of hypoxia and metabolite loads on the blood levels of octopine and related compounds

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Abstract
Male S. officinalis were subjected to hypoxia and the concentrations of blood metabolites were measured during stress and recovery. Blood octopine levels were elevated during hypoxia whereas blood glucose concentration declined. During recovery, octopine was rapidly cleared from the blood while blood glucose concentration increased, initially overshooting the control level, before returning to prehypoxia levels. The clearance of an octopine bolus (300 .mu.mol given i.v.) from the blood was followed. Octopine uptake from the blood was correlated with a transient rise in blood glucose concentration. Injection of an arginine bolus resulted in an increase in blood octopine levels, whereas a lactate bolus led to elevated blood glucose and octopine levels. Octopine concentration in cephalopod blood is modulated in response to physiological stress and octopine metabolism is closely integrated with the metabolism of glucose, arginine and lactate. The octopine produced during glycolytic muscular work is transported via the bloodstream for use as an aerobic substrate in other tissues. The inverse relationship between blood octopine and glucose levels suggests the presence of a modified Cori cycle in wich octopine released from muscle can be taken up by tissues capable of utilizing the compound as a gluconeogenic substrate.