A light and electron microscopic study correlating the chromaffin reaction and granule ultrastructure in the adrenal medulla of the Syrian hamster

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Abstract
The medullae from the right adrenal glands of hamsters given one or three injections of reserpine were prepared for electron microscopy by fixation in buffered osmic acid while the contralateral left glands were fixed in formol‐dichromate for light microscopic determinations of the chromaffin reaction. The adreno‐medullary cells of these animals were compared with cells of untreated hamsters in order to determine if catecholamine loss was accompanied by changes in the electron opaque cytoplasmic granules.Ten and 15 hours following one reserpine injection (1 mg/kg) the chromaffin reaction was positive, whereas after 20 hours the reaction was negative, reflecting a catecholamine reduction. The negative chromaffin reaction was accompanied by alterations in granule ultrastructure. The dense central core of the granules was less electron opaque compared with those of control medullary cells. The decreased density likely reflected a catecholamine loss since the opaque appearance of the granules is attributed to the presence of the amines. Following three injections (1 mg/kg daily; three days) the chromaffin reaction was negative and most granules had disappeared from the cytoplasm. The results give evidence that, after limited reserpine injections (1 mg/kg; one injection), catecholamines can be released from the medullary cells without granule disappearance.