VA Tennessee Valley Healthcare System 1 article published in JoVE Biology Human Pseudoislet System for Synchronous Assessment of Fluorescent Biosensor Dynamics and Hormone Secretory Profiles Tiffany M. Richardson*1, Yasminye D. Pettway*1, John T. Walker1, Heather A. Nelson2, Matthew Ishahak3, Gregory Poffenberger2, Radhika Aramandla2, Conrad Reihsmann2, Ashutosh Agarwal3, Alvin C. Powers1,2,4, Marcela Brissova2 1Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 2Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University Medical Center, 3Department of Biomedical Engineering, University of Miami, 4VA Tennessee Valley Healthcare System This protocol describes a method for the synchronous acquisition and co-registration of intracellular signaling events and the secretion of insulin and glucagon by primary human pseudoislets using the adenoviral delivery of a cyclic adenosine monophosphate (cAMP) biosensor, a cAMP difference detector in situ (cADDis), and a microperifusion system.