The unanswered question of high anaerobic capabilities of carp white muscle

Carp white muscle is considered to have a very high anaerobic capability; however, the accumulation of lactate is often not proportional to the amount of energy which must be generated. On the basis of whole-animal studies it is known that some fish produce NH4+ and CO2 anaerobically. This is interesting in light of the concept that many invertebrate facultative anaerobes simultaneously utilize carbohydrates and amino acids with the production of a variety of end products. We tested the hypothesis that in carp white muscle (a) lactate was not the sole end product of anaerobic metabolism and (b) amino acids were utilized as an anaerobic energy source. After an anaerobic work period induced by hypoxia we could detect none of the end products known to build up in invertebrate tissues and no mobilization of the free amino acid pool. Thus, carp white muscle appears to depend solely on glycogenolysis. The low level of lactate in carp white muscle even after severe hypoxic stress may be due to the transfer of this compound out of the tissue despite poor vascularization.