Calcium Regulation in Cardiac Muscle of the Southern Kingfish

Rebecca Ryznar and Cheryl Watson, Department of Biomolecular Sciences, Central Connecticut State University

Recent physiological investigations examining the cardiac calcium handling abilities of tuna and rainbow trout suggest increased reliance on sarcoplasmic reticulum calcium contribution for heart contractility that is both temperature and frequency dependent. Both of these fishes, more so tuna, have a high recorded heart rate compared to other species. There is also evidence to suggest that there is an increased SERCA-2 protein content which allows for more calcium uptake and ATPase activity in tuna. Of late it has been discovered that the southern kingfish, a species with a relatively modest lifestyle not requiring exceptional cardiac output function, produces a heart rate comparable to the most rapid rates observed in tuna and trout. Analyzing previous findings of SR calcium contribution in other fish with noted high heart rates, it seems that the southern kingfish is utilizing this mammalian like capability as well. In order to evaluate this hypothesis, cardiac function of isolated cardiac strips from the southern kingfish and croaker has been assessed in the presence of a low concentration of ryanodine (a biphasic compound which will either permanently block or open the ryanodine receptor) and epinephrine. Expression of specific excitation contraction components are examined for southern kingfish, tuna and croaker using immunofluorescent staining of sarcolemmal calcium ATPase, ryanodine receptor , L-Type calcium channel and phospholamban. Future experiments are discussed including additional force frequency experiments assessing cardiac function of southern kingfish and croaker in the presence of a high ryanodine concentration.

Presented April 21, 2007 at the 61st Annual Eastern Colleges Science Conference, College of Mount Saint Vincent, Riverdale NY