Local renin-angiotensin system is involved in K⁺-induced aldosterone secretion from human adrenocortical NCI-H295 cells

NCI-H295, a human adrenocarcinoma cell line, has been proposed as a model system to define the role of the renin-angiotensin system in the regulation of aldosterone production in humans. Because the precise cellular localization of the components of the renin-angiotensin system in human adrenal cortical cells remains unclear, we investigated their localization in this defined cell system. NCI-H295 cells expressed both angiotensinogen and renin as shown by reverse transcriptase polymerase chain reaction and immunohistochemistry. Human angiotensin-converting enzyme (ACE) was not detectable by immunocytochemistry, ACE binding, or reverse transcriptase polymerase chain reaction. However, 3.5 mmol/L K⁺ stimulated the formation of both angiotensin I and angiotensin II 1.9- and 2.5-fold, respectively, and increased aldosterone release 3.0-fold. The K⁺-induced stimulation of aldosterone release was decreased by captopril and enalaprilat (24% and 26%, respectively) and by the angiotensin type 1 (AT₁)-receptor antagonist losartan (28%). Angiotensin II-induced stimulation of aldosterone release was abolished by losartan treatment. Specific [¹²⁵I]Sar¹-angiotensin II binding was detected by receptor autoradiography. The binding of [¹²⁵I]Sar¹-angiotensin II was completely displaced by the AT₁ antagonist losartan but not by the AT₂ receptor ligand PD 123319, confirming the expression of angiotensin II AT₁ receptors in NCI-H295 cells. Our results demonstrate that NCI-H295 cells express most of the components of the renin- angiotensin system. Our failure to detect ACE, however, suggests that the production of angiotensin II in NCI-H295 cells may be ACE independent. NCI- H295 cells are able to produce angiotensin II, and K⁺ increases aldosterone secretion in part through an angiotensin-mediated pathway. The production of angiotensin II in NCI-H295 cells demonstrates that this human cell line can be useful to characterize the role of locally produced angiotensin II in the regulation of aldosterone release.