Concentrations of myoglobin and myoglobin mRNA in heart ventricles from Antarctic fishes

We used a combined immunochemical and molecular approach to ascertain the p resence and concentrations of both the intracellular oxygen-binding hemopro tein myoglobin (Mb) and its messenger RNA (mRNA) in 13 of 15 known species of Antaretic channichthyid icefishes, Mb protein is present in the hearts o f eight species of icefishes: Chionodraco rastrospinosus, Chionodraco hamat us, Chionodraco myersi, Chaenodraco wilsoni, Pseudochaenichthys georgianus, Cryodraco antarcticus, Chionobathyscus dewitti and Neopagetopsis ionah. Fi ve icefish species lack detectable Mb protein: Chaenocephalus aceratus, Pag etopsis macropterus, Pagetopsis maculatus, Champsocephalus gunnari and daco draco hunteri. Mb concentrations range from 0.44+/-0.02 to 0.71+/-0.08 mg M b g(-1) wet mass in heart ventricle of species expressing the protein. A Mb -mRNA-specific cDNA probe was used to quantify mRNA in five Mb-expressing i cefishes, Mb mRNA was found in low but detectable amounts in Champsocephalu s gunnari, one of the species lacking detectable Mb. Mb mRNA concentrations in heart ventricle from Mb-expressing species ranged from 0.78+/-0.02 to 1 6.22+/-2.17 pg Mb mRNA mu g(-1) total RNA), Mb protein and Mb mRNA are abse nt from the oxidative skeletal muscle of all icefishes, Steady-state concen trations of Mb protein do not parallel steady-state concentrations of Mb mR NA within and among icefishes, indicating that the concentration of Mb prot ein is not determined by the size of its mRNA pool.