Serotonin stimulates calcium influx in isolated rat adrenal zona glomerulosa cells

To investigate the role of calcium as a second messenger in serotonin-stimulated aldosterone secretion, radiolabelled calcium influx studies were carried out in purified rat adrenal zona glomerulosa cells using 45CaCl2. The results show that serotonin caused calcium influx within 45 seconds of addition and this continued for up to 105 seconds. Angiotensin II also caused calcium influx; however, the effect was significantly smaller than that of serotonin. Serotonin-stimulated calcium influx could be inhibited by the calcium antagonist verapamil and by methysergide, a selective serotonin receptor type-1/2 antagonist. The data indicate that serotonin directly stimulates calcium uptake in zona glomerulosa cells via calcium channels which are coupled to specific serotonin receptors.