Myoglobin deficiency in the hearts of phylogenetically diverse temperate-zone fish species

Previous studies relying upon spectrophotometric methods reported low levels of myoglobin, an intracellular oxygen-binding protein, in oxidative muscles of some sluggish benthic fishes distributed throughout the North Atlantic Ocean. Using immunochemical techniques we show that myoglobin is not expressed in the heart ventricles of Cyclop terus lumpus (Cyclopteridae), Anarhichas lupus (Anarhichadidae), Macrozoarces americanus (Zoarcidae), and Lophius americanus (Lophiidae). Hemitripterus americanus (Hemitripteridae) expresses myoglobin at 2.3 ± 0.2 mg·g wet mass–1 (mean ± SD). Myoglobin was not detected in oxidative skeletal muscle (pectoral adductor profundus) in either the white-hearted fishes examined or red-hearted H. americanus. Supporting these results, myoglobin messenger RNA was not detected in cardiac muscles of white-hearted fishes by means of either direct Northern blot analysis or by the reverse transcriptase – polymerase chain reaction followed by amplification of cDNA product. The partial cDN...