31P-nuclear-magnetic-resonance study of muscles from Mytilus edulis

Abstract

Phosphorus-31 nuclear magnetic resonance (NMR) spectra were recorded from freshly excised and resting anterior byssus rectractor muscles of the mussel Mytilus edulis.The absolute concentrations of phosphometabolites measured by NMR compare well with the values obtained by a biochemical method. Quantitative measurements were achieved in several minutes by applying to the obscrved NMR signals a correction taking the saturation effects into account.The time evolution of the phosphometabolite concentrations reveals that the hydrolysis of phosphoarginine is a first-order reaction producing inorganic phosphate, whilst the adenosine triphosphate level remains constant for more than 10 h.The phosphoarginine hydrolysis rate varies as a function of the season and reaches a maximum during the reproduction period of the mussel. This increase in phosphoarginine consumption could be bound up with the higher excitability of the muscles during spring. The activation energy of the phosphoarginine hydrolysis reaction also depends on the season and the difference between the value determined in winter and that measured in spring is explained by a modification of the mode of action or of the proportions of the enzymes involved in the muscular metabolism.Quantitative measurements of phosphometabolite concentrations of tissues in vivo are important for understanding the metabolic processes. 31P NMR is known as a good nondestructive and non-invasive method for this kind of study [l, 21. Different types of muscles have been examined using 31P NMR but only a small number of studies on invertebrate muscles have been performed up to now [3,4].Lamellibranches can avoid dessication by keeping their valves closed due to the tonic contraction of the smooth part of the adductor muscle. In this case the oxygen level rapidly decreases and the tissues are in non-aerobic conditions. The anterior byssus retractor muscle of the mussel Mytilus edulis is a smooth muscle that shows this tonic property even when isolated from the animal and separated from all nervous connections; the muscle keeps its functional properties when immersed in sea water in aerobic as well as anaerobic conditions. By following the time course of the oxygen consumption of the muscle in aerobic conditions, it has been shown that, in resting conditions, the metabolism is high (72 nmol g-' min-') when compared to other muscles in the same conditions [5]. In absence of oxygen, the resting metabolism seems to be so low that the biochemical methods are inadequate to measure the concentration variations of the chemical substances directly involved.Correspondence to A. Schanck, BHtiment Lavoisier, CPMC/CRIS, Place Louis Pasteur, 1, B-2348 Louvain-la-Neuve, BelgiumAbbreviations and Symbols. P-Arg, phosphoarginine; T,, nuclear spin-lattice relaxation time; IP-Argr integrated intensity of the phosphoarginine NMR peak; Ip,. integrated intensity of the Pi NMR peak; kp-Argr phosphoarginine hydrolysis rate constant; Tp, pulse interval; Q temperature coefficient.The aim of the present work...

Changes in sarcoplasmic metabolite concentrations and pH associated with the catch contraction and relaxation of the anterior byssus retractor muscle ofMytilus edulis measured by phosphorus-31 nuclear magnetic resonance

“…Immediately after the dissection, we observed a large P1 signal (concentration, 2-3/~mol g-l) which was presumably caused by excitation during the dissection procedure (Schanck et al, 1986). Following the perfusion with ASW, the Pi signal gradually decreased and reached an equilibrium (average concentration, 0.8/lmolg -1) within 1 h. The shape of the whole spectrum for the resting state was thereafter kept unchanged for more than 10 h. In some spectra with relatively low signal-fo-noise ratio, the small Pi signal often hindered the estimation [Pi]in and pHin (see below).…”

Modification of pyruvate kinase and lactate dehydrogenase in foot muscle of the sea mussel Mytilus galloprovincialis under anaerobiosis and recovery

“…Concentrations of ATP, ADP, phospho-arginine (functional analogue of phosphocreatine in molluscs), inorganic phosphate and pH in their muscle were changed under these conditions (8,12,13).…”

Phosphorus Metabolism Monitored by 31P NMR in Juvenile Sea Scallop (Placopecten magellanicus) Overwintering in Pearl Nets at a Nova Scotian Aquaculture Site

“…The TI values (in seconds) used in this study were obtained from adult scallop muscle tissue: Pi 3.3, Arg P 1.6, and ATP 0.4, 8.4, and 0.3 (a, P, and y phosphate residues, respectively). These values are similar to those reported for other molluscs (Bmow et al 1980;Ellington 1983b;Schanck et al 1986). Our spectra were routinely acquired with a recycle delay of 3 s. A longer recycle delay time was not used because the time allowable for signal acquisition from living tissues is limited by inherently low signal to noise ratios and the innate p r~b l e m in NMR in vivo measurements of maintaining physiologically appropriate steadystate conditions in the NMR tube during prolonged periods of data acquisition.…”