Total magnesium concentrations of perilymph, cerebrospinal fluid and blood in guinea pigs fed different magnesium-containing diets.

The total magnesium (Mg) concentrations of the perilymph (PL), cerebrospinal fluid (CSF), plasma and red blood cells (RBCs) of anesthetized guinea pigs separated into three groups and fed different Mg-containing diets were determined by atomic absorption spectrometry. Due consideration was given to the significant sources of error connected with the sampling procedure, particularly contamination of PL with CSF. The Mg levels of the individuals fluids differed significantly (P < 0.05/0.01) within each group. In the normal Mg group, the mean values of the PL, CSF and plasma were 0.66, 0.81 and 0.97 mmol/l, respectively, and 7.83 mmol/kg dry weight for RBCs. The analytical data were found to depend on the Mg content of the animals' diet, but to a different degree in the individual specimens (plasma > PL > CSF). A correlation was found to exist between all specimens tested (P < 0.05/0.01), except for CSF and RBCs, with the closest relation being that between plasma and PL. These findings suggest that the perilymphatic Mg equilibrates with the Mg level of plasma rather than with that of CSF. This is the first report showing Mg data of PL, CSF, plasma and RBCs obtained from the same subject, and the dependency on the Mg content of the animals' diet.