A Study of Calcium and Magnesium in the Cerebrospinal Fluid †

In the course of studies conducted in this laboratory on the distribution and concentration of metal ions in the central nervous system (CNS),'3 similar studies were made on the cerebrospinal fluid (CSF). Of the fifteen ions found in the CNS tissue, only four (Na, K, Mg, and Ca) were found consistently, and Cu occasionally in CSF. The role of magnesium in biological systems has been well studied.10"2'19 The r6le of calcium in the same systems is not so well understood. In general, it would appear that calcium and magnesium are antagonistic to each other in their action on enzyme systems. The mode and site of action of these antagonists is not clear but may involve the shifting of equilibria through activation or inhibition of different mutually dependent components of the same system.1' 6 11 3 16 17 20. M. There is also evidence that these ions may be competitive. Magnesium, the concentration of which is very important in cells where high metabolic activity or high energy production-requirement exists, has been shown to be required for the activation of most of the enzymes concerned with the transfer and removal of phosphate in biological systems.1' The CNS has been shown to have such an energy requirement.18 It has further been shown that the CSF is not a filtrate but is more in the nature of a dialysate of the plasma, and, while the origin of this fluid and the location of the barriers interposed between it and the blood are still a matter of controversy, nevertheless, it is generally accepted that this fluid is more nearly in equilibrium with the cells of the CNS than is the plasma." It seemed worthwhile, therefore, to make a study of magnesium and calcium in the CSF which might elicit some information of the metabolic components of the CNS cells since the interstitial fluid in which they are bathed closely resembles the CSF. A search of the literature revealed that the Clark-Collip method for the determination of calcium in the CSF was most widely used.' There was also