Research in our laboratory focuses on a class of intracellular ion channels know as ryanodine receptors (RyRs). In mammals, there are three RyR isoforms. RyR1 and RyR2 are the predominate isoforms in skeletal and cardiac muscle, respectively where they are the primary efflux pathway for the release of calcium from the sarcoplasmic reticulum to activate contraction. RyR3 has a wide tissue distribution and contributes to calcium regulation in a variety of cell types. RyRs are the largest known ion channel and are regulated by a multitude of endogenous effectors, including ions, metabolites and regulatory proteins. Therefore, an area of interest is the regulation of these RyR channels by endogenous effectors; especially as it relates to altered contractile function associated with cardiac and skeletal disease, skeletal muscle fatigue and aging. We analyze channel function on multiples levels of organization. Sarcoplasmic reticulum vesicle [3H]ryanodine binding is used to examine large populations of channels. Individual channels are incorporated into artificial lipid bilayers in order to record single channel currents and assess channel kinetics. Calcium release from permeabilized muscle fibers provides a method of examining RyR function in situ. My research has two long-range goals. The first is to understand how intracellular calcium is regulated and how alterations in the regulation effects cell function. The second goal is to understand the RyR regulatory sites that could potentially be exploited for the development of pharmacological compounds to treat disorders of cellular calcium regulation.