Combined stereological and biochemical analysis of storage and release of catecholamines in the adrenal medulla of the rat.

Adrenal medullae from rats injected with insulin 1 h prior to decapitation were analyzed by stereology and their catecholamine content was determined. In control animals the ratio between adrenaline- and noradrenaline- containing cells was 4.06 whereas the ratio between adrenaline and noradrenaline contents was 4.11. The glands from insulin-treated animals showed a 45% reduction in adrenaline content and a 42% decrease in the volumetric density of the adrenaline-containing granules. However, neither the noradrenaline content nor the volumetric density of noradrenaline-containing granules was modified in glands from insulin-treated animals. From these data, the amount and concentration of adrenaline or noradrenaline in a single granule have been calculated. The results are consistent with the view that chromaffin granules are the source of the released catecholamines. The present paper demonstrates that stereology combined with biochemistry is a useful tool for resolution of problems at the cellular and subcellular levels.