EFFECTS OF HYPOXIA AND TOXICANT EXPOSURE ON ARGININE KINASE FUNCTION AS MEASURED BY P-31-NMR MAGNETIZATION-TRANSFER IN LIVING ABALONE

The activity of arginine kinase (AK) was evaluated by saturation trans fer NMR in red abalone (Haliotis rufescens) in response to hypoxia, so dium azide (NaN3; an inhibitor of cytochrome c oxidase), or penta-chlo rophenol (PCP; an uncoupler of oxidative phosphorylation) exposure. Ps eudo-first order rate constants (K-for) in the forward (ATP forming) r eaction direction showed maximal increases from basal values of 0.025 s(-1) to 0.095, 0.114, 0.126 s(-1) for NaN3 hypoxia, and PCP exposures , respectively. Increases in K-for were inversely correlated (r(2) = 1 .00) to declines in ATP concentration in all exposed animals. Flux (th e product of K-for, and phosphoarginine concentration) appeared to con verge on a common value, from basal flux values of 0.257 mM PA s(-1) t o 0.703, 0.770, and 0.627 mM PA s(-1) for NaN3, hypoxia, and PCP expos ures, respectively. It seems likely that all three stresses were equal ly effective at inhibiting mitochondrial ATP formation, which may acco unt for the similarity in flux increase, possibly to maximal rates of AK-mediated ATP formation. Differences in K-for, are related to declin es in ATP concentrations, which appear to be stress specific, and like ly indicate additional mechanisms of toxicity for NaN3 and PCP. (C) 19 97 Elsevier Science Inc.