OBJECTIVE: The objective of the study was to delineate a process in human ZG, which may regulate both aldosterone production and cell turnover.
DESIGN: This study included a comparison of 20 pairs of ZG and zona fasciculata transcriptomes from adrenals adjacent to an APA (n = 13) or a pheochromocytoma (n = 7).
INTERVENTIONS: Interventions included an overexpression of the top ZG gene (LGR5) or stimulation by its ligand (R-spondin-3).
MAIN OUTCOME MEASURES: A transcriptome profile of ZG and zona fasciculata and aldosterone production, cell kinetic measurements, and Wnt signaling activity of LGR5 transfected or R-spondin-3-stimulated cells were measured.
RESULTS: LGR5 was the top gene up-regulated in ZG (25-fold). The gene for its cognate ligand R-spondin-3, RSPO3, was 5-fold up-regulated. In total, 18 genes associated with the Wnt pathway were greater than 2-fold up-regulated. ZG selectivity of LGR5, and its absence in most APAs, were confirmed by quantitative PCR and immunohistochemistry. Both R-spondin-3 stimulation and LGR5 transfection of human adrenal cells suppressed aldosterone production. There was reduced proliferation and increased apoptosis of transfected cells, and the noncanonical activator protein-1/Jun pathway was stimulated more than the canonical Wnt pathway (3-fold vs 1.3-fold). ZG of adrenal sections stained positive for apoptosis markers.
CONCLUSION: LGR5 is the most selectively expressed gene in human ZG and reduces aldosterone production and cell number. Such conditions may favor cells whose somatic mutation reverses aldosterone inhibition and cell loss.
METHODS: Ovariectomized female normotensive Wistar Kyoto (WKY) and Spontaneous hypertensive (SHR) rats were given six weeks treatment with testosterone via subcutaneous silastic implant. The rats were anesthetized and mean arterial pressure (MAP) was measured via direct cannulation of the carotid artery. Animals were sacrificed and kidneys were removed and subjected for α, β and γ-ENaC protein and mRNA expression analyses by Western blotting and Real-time polymerase chain reaction (qPCR), respectively. Distributions of α, β and γ-ENaC proteins in kidneys were observed by immunofluorescence. Plasma testosterone, aldosterone, electrolytes, osmolality, urea and creatinine levels were determined by biochemical assays. Analysis were also performed in non-testosterone treated orchidectomized and sham-operated male WKY and SHR rats.
RESULTS: Treatment of ovariectomized female WKY and SHR rats with testosterone causes increased in MAP but decreased in plasma aldosterone, sodium (Na+), osmolality and expression and distribution of α, β and γ-ENaC subunits in the kidneys. Orchidectomy decreased the MAP but increased plasma aldosterone, Na+, osmolality and α, β and γ-ENaC expression and distribution in the kidneys of male WKY and SHR rats.
CONCLUSIONS: Decreased in plasma aldosterone, Na+ and ENaC levels in kidneys under testosterone influence indicated that testosterone-induced increased in MAP were not due to increased plasma aldosterone and ENaC levels in kidneys, and thus the testosterone effect on MAP likely involve other mechanisms.