Meeting Abstract
P3.6 Tuesday, Jan. 6 Comparative Metabolic Biochemistry Of Shark Myocardial Tissue MARSHALL, H*; BERNAL, D; University of Massachusetts Dartmouth hmmarshall@gmail.com
Work on lamnid sharks (Family Lamnidae) has revealed their ability to undergo broad high-latitude migrations and rapid and repeated sojourns into depths below the thermocline. Both scenarios expose these fishes to cold temperatures. Lamnids have the ability to maintain their swimming muscles at temperatures above ambient (regional endothermy), and this quality may allow these sharks to sustain elevated muscle metabolic biochemical capacities when exposed to cold water. However, the lamnid heart does not benefit from regional endothermy and all myocardial tissues are at thermal equilibrium with ambient temperatures. Proper cardiac function is essential for providing lamnids with adequate supplies of oxygenated blood for maintained swimming muscle function. Thus, a heart that is exposed to prolonged cold or rapidly fluctuating ambient temperatures should be capable of maintaining elevated metabolic biochemical capabilities. The objective of this study was to compare the activities of citrate synthase (CS) and lactate dehydrogenase (LDH) in the myocardial tissue of lamnid and non-lamnid sharks at various temperatures in order to determine how enzyme activities are affected. Analysis shows that CS activity is significantly higher at 20C for lamnid sharks (24.2+/-3.4 IU g-1) relative to non-lamnids (12.6+/-1.5 IU g-1). LDH activity is also significantly higher in lamnids (169.8+/-52.2 IU g-1) relative to non-lamnids (109.6+/-19.6 IU g-1). There was no significant difference in the thermal rate coefficients (Q10) at 10-30C between lamnids (1.58+/-0.4) and non-lamnids (1.56+/-0.2) for CS. The Q10 values at 10-30C for LDH also showed no differences between lamnids (1.71+/-0.3) and non-lamnids (2.22+/-0.4). It appears that lamnids have higher cardiac enzyme activities than non-lamnids, but are similarly affected by temperature changes.
