Role of Voltage-gated Calcium Channels in the Regulation of Aldosterone Production from Zona Glomerulosa Cells of the Adrenal Cortex

Zona glomerulosa cells (ZG) of the adrenal gland constantly integrate fluctuating ionic, hormonal and paracrine signals to control the synthesis and secretion of aldosterone. These signals modulate Ca levels, which provide the critical second messenger to drive steroid hormone production. Angiotensin II is a hormone known to modulate the activity of voltage-dependent L- and T-type Ca channels that are expressed on the plasma membrane of ZG cells in many species. Because the ZG cell maintains a resting membrane voltage of approximately -85 mV and has been considered electrically silent, low voltage-activated T-type Ca channels are assumed to provide the primary Ca signal that drives aldosterone production. However, this view has recently been challenged by human genetic studies identifying somatic gain-of-function mutations in L-type Ca 1.3 channels in aldosterone-producing adenomas of patients with primary hyperaldosteronism. We provide a review of these assumptions and challenges, and update our understanding of the state of the ZG cell in a layer in which native cellular associations are preserved. This updated view of Ca signalling in ZG cells provides a unifying mechanism that explains how transiently activating Ca 3.2 channels can generate a significant and recurring Ca signal, and how Ca 1.3 channels may contribute to the Ca signal that drives aldosterone production.