Intracellular
calcium (Ca) levels play pivotal roles in
aldosterone biosynthesis. Several somatic mutations of
ion channels associated with
aldosterone over-production were reported to result in over-inflow of Ca ion. Recently, the main regulators of extracellular Ca including VDR, CaSR and PTH1R were also reported to regulate steroidogenesis including
aldosterone production. Therefore, not only intracellular but also extracellular Ca levels could regulate
aldosterone biosynthesis. In addition, primary
aldosteronism (PA) is clinically associated with not only more frequent cardiovascular events but also secondary metabolic disorders including abnormal
calcium metabolism,
osteoporosis and others. However, the details of Ca metabolic abnormalities associated with, including the potential correlation between those abnormalities and
aldosterone overproduction, have remained virtually unknown. Therefore, in this study, we first immunolocalized Ca metabolism-related receptors (CaSR, VDR and PTH1R) in normal adrenal glands (
NAs),
aldosterone-producing
adenomas (APAs) and
cortisol-producing
adenoma (CPA). We then compared the findings with clinicopathological parameters of these patients and the patterns of KCNJ5 somatic mutation of the
tumors among APA patients. In vitro study was also performed to further explore the potential effects of extracellular Ca, PTH,
Vitamin D and
ionophore on
aldosterone production. Ca metabolism-related receptors were predominantly localized in
aldosterone-producing cells (ZG and APA) in both immunohistochemistry and qRT-PCR analysis.
CYP11B2 mRNA was significantly increased by CaCl2 treatment and further by adding
ionophore. All the key
enzymes related to
aldosterone and
cortisol biosynthesis including
CYP11B2, CYP17A1 and
CYP11B1 were upregulated by PTH treatment in this model and PTH could serve as a co-stimulator of ANG II to increase
CYP11B2 expression. VDR
mRNA levels were positively correlated with those of
CYP11B2, CYP17A1 and
CYP11B1 in APA
tumor tissues and significantly higher in KCNJ5 mutated APAs than wild type.
CYP11B1 levels were also significantly increased by VitD treatment. PTH1R
mRNA levels were positively correlated with those of CYP17A1 and
CYP11B1, both involved in
cortisol production. In addition, the status of VDR was correlated with TRACP-5b levels, and that of PTH1R with serum Ca levels as well as urinary Ca excretion, respectively. Results of our present study did firstly demonstrate that
aldosterone-producing cells were more sensitive to the fluctuations of extracellular Ca levels and Ca metabolism could directly influence steroidogenesis, especially "neoplastic" co-secretion of
aldosterone and
cortisol in APA patients.