WATSON ET AL.: ETIOLOGY OF BURNT TUNA 



higher maximum circulating catecholamine lev- 

 els or to maintain high levels for longer periods, 

 thus explaining the greater number of female fish 

 that become burnt and the seasonality of the oc- 

 currence of burnt tuna. 



As pointed out by Davie and Sparksman (1986) 

 and Hochachka and Brill (1987), burnt tuna is a 

 quantitative change in tissue decomposition, not 

 a qualitative one. High blood catecholamine lev- 

 els at the time of death act as accelerators in this 

 inevitable metabolic cascade. However, because 

 we are dealing with a change in rate, the action of 

 catalysts can make all the difference as to 

 whether or not a fish becomes burnt due to CANP. 



FUTURE RESEARCH 



Under normal conditions, CANP is inhibited by 

 calpastatins. This class of proteins is distinct from 

 the other cysteine protease inhibitors, the cys- 

 tatins. Although the cystatins can inhibit cathep- 

 sins B and H, they are unable to alter CANP 

 activity. Conversely, calpastatin is only effective 

 against calcium-activated neutral protease (Bar- 

 rett et al. 1986; Parkes 1986). Unfortunately, al- 

 most nothing else is known about the relationship 

 of CANP to its endogenous inhibitor, either struc- 

 turally or physiologically. Certainly investiga- 

 tions into the role of calpastatin would prove 

 valuable for this research. 



Immediate future research will concentrate on 

 tracking the specific action of CANP in burnt 

 tuna and attempting to stop this action with Ca^ ^ 

 chelating agents such as EGTA (ethyleneglycol- 

 bis-(aminoethyl ether )-N,N,N',N'-tetraacetic 

 acid) or by use of its intracellular inhibitor, cal- 

 pastatin. Also, blood catecholamine levels of 

 stressed and unstressed fish will be measured, 

 along with metabolic clearance rates of nore- 

 pinephrine and epinephrine. 



When viewed as a process of metabolic deregu- 

 lation of CANP, the rapid deterioration of tuna 

 muscle ceases to be an isolated muscular phe- 

 nomenon. The Z-disc disintegration characteris- 

 tic of burnt tuna is also present in cardiac muscle 

 injury due to ischemia and muscular dystrophy 

 (Sugita et al. 1984). Given the highly conserved 

 nature of muscle tissue, an understanding of 

 burnt tuna may also provide insights into the 

 metabolic processes of human disease. 



ACKNOWLEDGMENTS 



This research was supported by a grant to 



Pacific Gamefish Research Foundation from the 

 Department of Land and Natural Resources, Di- 

 vision of Aquatic Resources, State of Hawaii. 



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