Sublethal effects of pentachlorophenol and hypoxia on rates of arginine kinase flux in red abalone ( Haliotis rufescens) as measured by 31P magnetization saturation transfer NMR

Abstract

Previous studies have demonstrated 31P nuclear magnetic resonance (NMR) to be a sensitive technique in assessing biochemical effects of sublethal toxicant exposure in live, intact marine organisms. This study builds upon previous work using 31P NMR magnetization saturation transfer techniques to determine rates of exchange through the arginine kinase (AK) reaction. The objective of this study is to compare rates of AK flux during exposure of red abalone ( Haliotis rufescens) to pentachlorophenol (PCP; an uncoupler of mitochondrial oxidative phosphorylation) or hypoxia. Utilizing a teflon and silicon flow-through exposure system, pseudo-first-order rate constants are determined for the ATP-forming direction of the AK reaction during 2-h exposure and 6-h recovery of abalone to 1.2 ppm PCP, or hypoxia by the cessation of water flow. Preliminary results show that AK rates increase during hypoxia, peaking in the first hour of resumed water flow, indicating an increased metabolic demand for ATP production through phosphoarginine hydrolysis during hypoxia and the initial stages of recovery. In contrast, AK flux rates remain low during PCP exposure and several hours into the recovery period, even though the toxic responses, i.e. changes in inorganic phosphate and phosphoarginine concentration, are similar for both exposure regimes. These results provide supporting evidence for a recently described new mechanism of action of PCP by AK inhibition. This study demonstrates a sensitive new method for evaluating sublethal effects of toxicants on a vital biochemical marker in intact marine organisms.