Meeting Abstract

P2.179  Saturday, Jan. 5  Creatine kinase isoforms differ between hearts of red- and white-blooded Antarctic fishes DULLEN, K.R.*; ORCZEWSKA, J.I.; ORTEGO, M.; O’BRIEN, K.M.; Univ of Alaska Fairbanks; Univ of Alaska Fairbanks; Univ of Alaska Fairbanks; Univ of Alaska Fairbanks krdullen2@alaska.edu

Creatine kinase (CK) produces creatine phosphate, shutting energy between mitochondria and myofibrils in muscle, and may also shuttle phospholipids from the outer to inner mitochondrial membrane. There are three isoforms of CK. Sarcomeric and ubiquitous (sMtCK and uMtCK) are in mitochondria; muscle (mmCK) is in the cytosol. Antarctic icefishes, lacking the oxygen-binding protein hemoglobin have significantly higher densities of mitochondria in heart ventricles compared to closely related red-blooded notothenioids. Mitochondria from icefishes are also larger with less densely packed cristae compared to red-blooded fishes. We hypothesized that CK distribution and isoform expression might differ between hearts of red- and white-blooded fishes due to differences in mitochondrial morphology and diffusion distances. CK transcript levels, isoform distribution and maximal activities were measured in hearts of red- and white- blooded notothenioids. Maximal activity of CK per g tissue was equivalent among most red- and white-blooded fishes but distribution of isoforms differed. The mitochondrial isoforms were not detected in icefishes by western blotting, nor were transcript levels of sMtCK using quantitative PCR. All three isoforms were detected in red-blooded fishes, and mRNA and protein mmCK were detected in icefishes. Consistent with this, the activity of CK was significantly higher in mitochondria of red-blooded fishes and nearly undetectable in icefish, and significantly higher in the cytosol of icefishes compared to most red-blooded fishes. The lack of mitochondrial CK in hearts of icefish may restrict the transfer of phospholipids to the inner membrane and contribute to their unusual morphology.