NMR Evidence for Complexing of Na+ in Muscle, Kidney, and Brain, and by Actomyosin. The Relation of Cellular Complexing of Na+ to Water Structure and to Transport Kinetics

Abstract

The nuclear magnetic resonance (NMR) spectrum of Na + is suitable for qualitative and quantitative analysis of Na + in tissues. The width of the N M R spectrum is dependent upon the environment surrounding the individual Na + ion. N M R spectra of fresh muscle compared with spectra of the same samples after ashing show that approximately 70 % of total muscle Na + gives no detectable N M R spectrum. This is probably due to complexation of Na + with macromolecules, which causes the N M R spectrum to be broadened beyond detection. A similar effect has been observed when Na + interacts with ion exchange resin. N M R also indicates that about 60 % of Na + of kidney and brain is complexed. Destruction of cell structure of muscle by homogenization little alters the per cent complexing of Na +. N M R studies show that Na + is complexed by actomyosin, which may be the molecular site of complexation of some Na + in muscle. The same studies indicate that the solubility of Na + in the interstitial water of actomyosin gel is markedly reduced compared with its solubility in liquid water, which suggests that the water in the gel is organized into an icelike state by the nearby actomyosin molecules. If a major fraction of intraceUular Na + exists in a complexed state, then major revisions in most theoretical treatments of equilibria, diffusion, and transport of cellular Na + become appropriate. I N T R O D U C T I O NMost investigators have assumed t h a t the N a + of the cell was largely in free solution in intracellular water. T h e opposite conclusion was d r a w n f r o m the application of a kinetic theory of Cope (1) to V a n der Kloot's d a t a (2) on N a +

Flow Thresholds for Cerebral Energy Disturbance and Na+ Pump Failure as Studied by in vivo 31P and 23Na Nuclear Magnetic Resonance Spectroscopy

“…The 23Na signal drop is therefore not attribut able to changes in relaxation time caused by ischemia. It is considered that this drop in 23Na signal intensity may result from movement of23Na into the intracellular space, as 60-70% of the intracellular 23Na in the brain seems to be invisible by NMR methods (Cope, 1967). In this study, the remarkable drop in 23Na signals intensity was thought to reflect disruption of the N a + pump activity.…”

The effect of sodium concentration on the content and distribution of sodium in the frog skin

“…(b) Na is fixed to the substance which fills the intercellular space (Farquhar & Palade, 1965).This space is opened toward the inside permitting a ready exchange with the inner solution, but closed on the outside by the maculae occludens. The large extent of complexing of Na in living tissues is a very well-known phenomenon in many other tissues (Shaw & Simon, 1955;Ling, 1962;Troshin, 1966;Cope, 1967). In fresh muscle, for instance, only 30 % of the Na is detectable by nuclear magnetic resonance analysis (Cope, 1967).…”

“…The large extent of complexing of Na in living tissues is a very well-known phenomenon in many other tissues (Shaw & Simon, 1955;Ling, 1962;Troshin, 1966;Cope, 1967). In fresh muscle, for instance, only 30 % of the Na is detectable by nuclear magnetic resonance analysis (Cope, 1967). Therefore, if the intercellular space were filled with an ion binding substance, it would not be surprising that it would show the properties assigned to the ENTC.…”

Factors affecting 39K NMR detectability in rat tissue

“…Measurements of the 39K NMR signal in biological tissues (1)(2)(3)(4) have shown that not all the potassium present is detectable when compared to chemical analysis methods such as atomic emission or absorption spectroscopy. Many of these studies showed the relative amount of potassium detected, commonly termed NMR visibility, to be around 40%, although there was some variability between tissues (1)(2)(3)(4).…”

“…Many of these studies showed the relative amount of potassium detected, commonly termed NMR visibility, to be around 40%, although there was some variability between tissues (1)(2)(3)(4). The 40% visibility figure has been rationalized as consistent with certain spectral characteristics arising from the quadrupolar relaxation of this spin-; nucleus.…”