High blood pressure (hypertension) is one of the leading epidemics in the United States of America with over three million cases per year. Aldosterone is a hormone that regulates blood pressure. My lab is interested in aldosterone driven hypertension. Thus, we aim to understand how aldosterone-producing zona glomerulosa (zG) cells are regulated and how their organization in rosette structures in the outermost layer of the adrenal gland modulates their activity. Specifically, my research focuses on measuring the calcium response of the zG layer to Angiotension II (Ang II), a peptide that strongly increases aldosterone production. We used mice expressing GCaMP3, a fluorescent calcium sensor delivered specifically to zG cells. Using wide-field fluorescent microscopy, we tested different concentrations of Ang II (50pM-1uM) and measured evoked calcium oscillations in zG cells. We analyzed the number of zG cells activated by a single dose of Ang II and the level of cell activity. We calculated the fraction of active cells and the EC50 for cell activation. To date, we find that Ang II dose-dependently increases the fraction of active cells in the zG layer. We are working on determining whether zG cells demonstrate different sensitivities to Ang II stimulation (i.e. different EC50s), and whether sensitive cells are more likely to be located next to sensitive or non-sensitive cells, forming clusters of activities. I hope that my data will help me understand the nature of the zG rosette structure, and thus, may contribute to the development of new pharmacological tools to treat aldosterone-associated hypertension.