Detection of Na+ and K+ in the Rat Adrenal Cortex with the Electron Microprobe

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Abstract
In order to demonstrate whether modification of aldosterone secretion is mediated by parallel changes of K+ in the adrenal zona glomerulosa, the total (intracellular + extracellular) Na+ and K+ content of the rat adrenal cortex was determined with the electron microprobe. Groups of rats were submitted to 1 of the following dietary regimens:standard, low Na+, high K+ or high Na+. Distribution of Na+ and K+ across the zona glomerulosa and zona fasciculata was compared. Standards of known electrolyte concentration were also analyzed. [Na+] was apparently greater in the zona glomerulosa than in the zona fasciculata, but K+ was distributed evenly in both zones. This was independent of dietary regimen. Aldosterone production, assessed by plasma aldosterone concentrations, could not be correlated with zona glomerulosa K+ content.