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A New Protocol for the Measurement of Picomole Quantities of Magnesium in Rat Renal Tubular Fluid

A New Protocol for the Measurement of Picomole Quantities of Magnesium in Rat Renal Tubular Fluid

J D Kibble, N Audsley, J P Day, R Green

Exp Physiol. 1998 Jan;83(1):11-22.

PMID: 9483416

Abstract:

The analysis of picomolar quantities of magnesium by electrothermal atomic absorption spectrophotometry (EAAS) was studied using a Perkin-Elmer-Zeeman 3030 spectrophotometer. The absorbance signal was not heavily dependent on the atomization temperature, but was greatly reduced when ashing temperatures in excess of 1200 degrees C were applied. The magnesium signal was significantly depressed in the presence of excess chloride in the sample matrix. However, use of NH4NO3 as a matrix modifier was sufficient to overcome this artefact. The analytical sensitivity was 0.15 absorbance units pmol-1 and the detection limit was 0.04 pmol. Using nanolitre constriction pipettes to dispense standards, the mean coefficient of variation was 5%. Measurement of magnesium handling in the rat proximal convoluted tubule revealed a significant correlation between the tubular fluid-to-plasma ultrafiltrate (TF/UF) concentration ratio for magnesium and the tubular fluid-to-plasma (TF/P) concentration ratio for [3H]inulin (r2 = 0.56, n = 17). This indicated that magnesium is concentrated during its passage along the proximal tubule. In contrast, this was not the case for sodium (r2 = 0.11, n = 16). Mean (TF/UF)Mg (1.16 +/- 0.07, n = 17) for random punctures was significantly greater than that for sodium ((TF/UF)Na = 1.02 +/- 0.02, n = 16). Despite concentration of magnesium in the lumen, significant net reabsorption of magnesium was observed along the length of the tubule (fractional reabsorption, FRMg = 19.4 +/- 3.0%, n = 17). In conclusion, EAAS provides a highly sensitive, reproducible and technically simple method for measuring picomolar quantities of magnesium in renal tubular fluid.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP13446189-A	Magnesium matrix modifier		13446-18-9	Price

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