Meeting Abstract

43.5  Jan. 6  SEX DIFFERENCES IN TELEOST CARDIAC BIOCHEMISTRY AND PHYSIOLOGY: WHAT HAVE WE BEEN MISSING? BATTIPROLU, Pavan K*; FARRAR, Richard S; HARMON, Kelli J; PIERSON, Nicholas S; RODNICK, Kenneth J; Idaho State University battpava@isu.edu

Unlike numerous mammalian studies, studies of cardiac physiology and metabolism in fishes have paid little attention to sex or the possibility of sex differences. We determined effects of glucose, sex steroids, and Ca²⁺ on cardiac contractility and metabolism in sexually immature, male and female trout. We also measured stored energy (glycogen, protein and triglycerides) in cardiac tissue. Fish were euthanized by blunt trauma. Ventricles were either 1) frozen rapidly and assayed for stored energy substrates or 2) dissected into uniform strips, attached to isometric force transducers, stretched to 90% of L_max, and electrically-stimulated at 0.5 Hz under aerobic conditions in either glucose or substrate-free media for 60 min at 14�C. Strips were treated with either testosterone or estradiol and controls received glucose or substrate-free conditions for the duration of experiments during which twitch force (F) and media metabolites were measured. Our results demonstrate that 1) cardiac glycogen was higher in males compared with females; 2) exogenous glucose (independently) and testosterone (males) or estradiol (females) all promoted F; however, increments in contractility were greater in males; 3) lactate release was 2-fold greater in females; and 4) female ventricle strips were more sensitive to Ca²⁺ than males. Similar to mammalian studies, our findings suggest that sex differences exist in cardiac energy metabolism, hormone responsiveness and Ca²⁺ sensitivity. Future studies should document and consider sex as an important variable for cardiac metabolism and performance in fishes. Funded by NIH P20RR16454, NSF-Idaho EPSCoR EPS-0447689, and NSF IOB-517669