Meeting Abstract

P3.113  Jan. 6  Effects of Body Size and Sex on Cardiac Citrate Synthase Activity in Rainbow Trout (Oncorhynchus mykiss) ANANTHAKRISHNAN, Gayathri*; BATTIPROLU, Pavan K; RODNICK, Ken J; Idaho State University anangaya@isu.edu

Citrate synthase, the initial enzyme of the tricarboxylic acid cycle, is a key enzyme for mitochondrial oxidation and energy production. Evidence also suggests that citrate synthase activity (CSA) is a valid marker of mitochondrial content in fish muscle. Whether the activity of citrate synthase in the heart varies with fish size or sex is not known. We therefore measured CSA in ventricles from different size, male and female rainbow trout. Our working hypothesis was that increase in body size leads to an increase in CSA. Ventricles from 17- 34 g (group I), 150-600 g (group II), and 600-1800 g (group III) males and females were excised, freeze clamped and kept frozen until assayed. CSA was measured at 15�C using whole tissue homogenates and standard assay techniques. Results: The group II fish (males and females) had ~2-fold higher CSA compared with the group I fish (P<0.001). Additionally in group II, males had 30% greater CSA than females (P<0.01) despite equal ventricle masses. CSA did not appear to increase in group III when compared to group II. Conclusion: The data supports our hypothesis that increased body size in both sexes increases cardiac CSA. This suggests that 1) body size affects cardiac energetics in rainbow trout and 2) ventricles of group II males have a greater capacity for aerobic energy metabolism than females in this size range. Funded by NIH P20RR16454, NSF-Idaho EPSCoR EPS-0447689 and NSF IOB- 0517669.