THE IMPACT OF ADULT AND LIFELONG HYPOXIA ON VENTRICLE PHENOTYPE IN ZEBRAFISH (DANIO RERIO).

Abstract

Hypoxia occurs naturally in a wide range of aquatic ecosystems. However, the physiological and morphological effects of prolonged hypoxia on organ systems remain poorly understood, especially in the cardiovascular system of fishes. We assessed contractile force of isolated hearts from adult zebrafish from control conditions (PO₂ = 21kPa), from adults after a 4-week exposure to hypoxia (PO₂ = 10kPa), or from adults exposed to lifelong hypoxia (PO₂ = 10kPa) throughout development, from egg to adult. Isolated ventricle contractility measurements were conducted during two challenges: increasing stimulation frequency (force-frequency) and during acute hypoxia exposure. All contractile parameters were at least 35% greater in lifelong hypoxic fish compared to control fish while heart mass was significantly smaller in lifelong hypoxic fish compared to controls. However, there were no differences in in the response to force-frequency protocol or graded acute hypoxia. Thickness of the ventricle's compact myocardium was increased ~35% by lifelong hypoxia but not by 4 weeks of hypoxia as adults compared to the control fish. Further, mitochondrial abundance did not significantly change. Collectively, these data suggest that early life hypoxia has major effects on remodeling cardiac tissue and performance in zebrafish.