(full paper is archived in the Miller Library)
Title: Differential enzyme activities of red and white muscle along the thermal gradient in Kawakawa
Student Author(s): Juul-Dam, Tina
Faculty Advisor(s): Somero, George N.
Location: Final Papers Biology 175H
Date: June 1996
Abstract: Tunas increase their core body temperature through endothermy, creating a gradient of increasing temperature from the skin to the core. I examined biochemical adaptations such as isozyme expression and temperature compensation of enzyme activity in muscle at different positions along the 4.8 C gradient in kawakawa (Euthynnus affinis). Studies in fishes have demonstrated that temperature changes cause differential expression of the two isozymes - thermostable and thermolabile - of malate dehydrogenase (MDH). These observations prompted me to determine MDH thermostability (ratio of thermostable to thermolabile isozymes) in tuna muscles along the temperature gradient. Contrary to expectation, MDH thermostability in red muscle appeared to decrease and in white muscle remained constant along the gradient from skin to core. MDH thermostability was consistently higher in white muscle than red muscle, possibly due to differential metabolic requirements of red and white muscle. Furthermore, citrate synthase (CS), lactate dehydrogenase (LDH), and MDH activities were measured to determine whether they changed according to the thermal gradient. Neither red nor white muscle showed a change in enzyme activities according to the temperature difference from skin to core.