[Acetylcholine and A23187 stimulate epinephrine secretion of isolated rat adrenal medulla cells in vitro].

Acetylcholine and A23187, two acetylcholinergic agonists, were used to induce the stimulus-secretion coupling of the isolated rat adrenal medulla cells. Morphometry of numerical density and electron probe X-ray quantitative microanalysis were adopted to measure the alterations in the number and calcium content of chromaffin granules in adrenal medulla cells during the agonist treatment. Secretion of epinephrine was detected by the high performance liquid chromatography (HPLC). It was found that the Ca content of the isolated rat adrenal medulla chromaffin granules dropped significantly after a 10-min incubation with the agonists, whereas the number of chromaffin granule decreased slowly during the agonist treatment and the epinephrine concentration raised significantly after a 20-min incubation with the agonists. The decrease of granule Ca content occurred earlier than the increase of epinephrine concentration, suggesting that the calcium released from chromaffin granule may in part account for the induced cell secretion.