The Impact of Mitochondrial and Thermal Stress on the Bioenergetics and Reserve Respiratory Capacity of Fish Cell Lines

Abstract

Various stressors affect the health of wild and cultured fish and can cause metabolic disturbances that first manifest at the cellular level. Here, we sought to further our understanding of cellular metabolism in fish by examining the metabolic responses of cell lines derived from channel catfish Ictalurus puntatus (CCO), white bass Morone chrysops (WBE), and fathead minnow Pimephales promelas (EPC) to both mitochondrial and thermal stressors. Using extracellular flux (EF) technology, we simultaneously measured the oxygen consumption rate (OCR; a measure of mitochondrial function) and extracellular acidification rate (ECAR; a surrogate of glycolysis) in each cell type. We performed a mitochondrial function protocol whereby compounds modulating different components of mitochondrial respiration were sequentially exposed to cells. This provided us with basal and maximal OCR, OCR linked to ATP production, OCR from ion movement across the mitochondrial inner membrane, the reserve capacity, and OCR independent of the electron transport chain. After heat shock, EPC and CCO significantly decreased OCR and all three cell lines modestly increased ECAR. After heat shock, the reserve capacity, the mitochondrial energetic reserve used to cope with stress and increased bioenergetic demand, was unaffected in EPC and CCO and completely abrogated in WBE. These findings provide proof-of-concept experimental data that further highlight the utility of fish cell lines as tools for modeling bioenergetics.

Received April 12, 2012; accepted August 5, 2012

ACKNOWLEDGMENTS

The authors thank Matt Barnett for his technical assistance and expertise. We also thank Bradley Farmer, Ken Davis, Dave Straus, and Kyle Feeley for carefully reviewing the manuscript. This study was funded by the U.S. Department of Agriculture (USDA), Agricultural Research Service under project number 6225-31630-006-00. The USDA is an equal opportunity provider and employer. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA.