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Effects of temperature, epinephrine and Ca²⁺ on the hearts of yellowfin tuna (Thunnus albacares)

Jason M. Blank¹, Jeffery M. Morrissette¹, Peter S. Davie² and Barbara A. Block^1,*

¹ Tuna Research and Conservation Center, Stanford University, Hopkins Marine Station, Oceanview Boulevard, Pacific Grove, CA 93950, USA
² Comparative Physiology and Anatomy, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, New Zealand

View larger version (17K): [in a new window]   Fig. 1. Values of cardiac parameters recorded from spontaneously beating yellowfin tuna hearts in situ at temperatures of 10 to 25 °C. (A) Heart rate, (B) stroke volume, (C) cardiac output, (D) myocardial power output. Standard conditions are shown as open symbols, maximal conditions as filled symbols. N=5 at 15 and 20 °C, N=4 at 10 and 25 °C. Values are means ± S.D. One value is given for heart rate at 7.4 °C.

View larger version (20K): [in a new window]   Fig. 2. Effects of external [Ca2+] on cardiac parameters recorded from spontaneously beating yellowfin tuna hearts in situ at 20°C. Data shown are for standard conditions (Heart rate), maximum flow (Stroke volume, Cardiac output) and maximum power (Power). Values are means + S.D. N=4. An asterisk indicates a value significantly different from the value at 1.8 mmol l-1 Ca2+. A dagger indicates a value significantly different from the value at 3.7 mmol l-1 Ca2+.

View larger version (22K): [in a new window]   Fig. 3. Effects of perfusate [epinephrine] on cardiac parameters recorded from spontaneously beating yellowfin tuna hearts in situ at 20°C. Data shown are for standard conditions (Heart rate), maximum flow (Stroke volume, Cardiac output) and maximum power (Power). Values are means + S.D. N=4. There are no significant differences among data points for a given parameter.

View larger version (10K): [in a new window]   Fig. 4. Scope for increase in cardiac output (open symbols) and myocardial power output (filled symbols) of in situ perfused yellowfin tuna hearts at temperatures of 10-25°C. Scope is determined as the percentage difference between mean values at standard and maximal flow (cardiac output) or maximal power (power output) conditions.