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

The total magnesium (Mg) concentrations of the perilymph (PL), cerebrospina l fluid (CSF), plasma and red blood cells (RBCs) of anesthetized guinea pig s separated into three groups and fed different Mg-containing diets were de termined by atomic absorption spectrometry. Due consideration was given to the significant sources of error connected with the sampling procedure, par ticularly contamination of PL with CSF. The Mg levels of the individuals fl uids differed significantly (P < 0.05/0.01) within each group. In the norma l Mg group, the mean values of the FL, CSF and plasma were 0.66, 0.81 and 0 .97 mmol/l, respectively, and 7.83 mmol/kg dry weight for RBCs. The analyti cal data were found to depend on the Mg content of the animals' diet, but t o a different degree in the individual specimens (plasma > PL > CSF). A cor relation was found to exist between all specimens tested (P < 0.05/0.01), e xcept for CSF and RBCs, with the closest relation being that between plasma and FL. These findings suggest that the perilymphatic Mg equilibrates with the Mg level of plasma rather than with that of CSF. This is the fi:rst re port showing Mg data of FL, CSF, plasma and RBCs obtained from the same sub ject, and the dependency on the Mg content of the animals' diet.