The overall goal of this procedure is the parallel assessment of circadian bioluminescence and the secretory activity of human primary endocrine cells cultured and synchronized en vitro.This method can help to investigate the temporal pattern of cell secretion and how it can be regulated by cell-autonomous circadian clocks.The main advantage of this technique is that it allows us to monitor the circadian luciferins as reporter activity and, simultaneously collect outflow medium for measuring the levels of secreted hormones and myokines.To introduce circadian bioluminescence reporters into primary cells by lentiviral transduction, first, transfer the 3.5 cm petri dishes containing human myoblasts at 30%to 50%confluency to a laminar flow cabinet.Replace the human myoblast medium with 2 mL of growth medium.Then transduce the primary cell culture by pipetting lentivirus solution into the dish to obtain a multiplicity of infection equal to three.Incubate the cells overnight in a tissue-culture incubator.Change medium the next day.To achieve en vitro synchronization, add 10 micromolar adenylyl cyclase activator in 2 mL of medium per 3.5 cm petri dish containing the previously transfected primary cells.Incubate the cells for 60 minutes at 37
