Regulation of mineralocorticoid biosynthesis by calcium and the StAR protein.

In adrenal zona glomerulosa cells, the calcium messenger system is the major signaling mechanism activated by physiological stimulators of aldosterone production. We present here evidence for a dual site of action of the calcium signal: 1) Calcium influx into the mitochondrion is a prerequisite to the activation of steroidogenesis. This calcium entry leads to a rise in mitochondrial calcium concentration and to an increase in intramitochondrial cholesterol transfer and Steroidogenic Acute Regulatory (StAR) protein accumulation in inner mitochondrial membranes. 2) Calcium also exerts a genomic regulatory effect by activating transcription of the StAR gene.