Ultraviolet polarized light study on isolated myocardial trabeculae and skeletal fibers

The main components of the excitable membranes are protein and lipoproteins absorbing in the ultraviolet. Contractile proteins in muscle also absorb ultraviolet light. If polarized light is used, it becomes possible to distinguish the orientation of the absorbing groups either at rest or during activity. A system of microspectrophotometry in vivo using polarized ultraviolet light has been established to study the portion of myocardial trabeculae or of skeletal fibers in the central compartment of a double sucrose gap apparatus. Thus the system also allows electrophysiological studies. On both preparations, a relation between the absorbance change at 280 nm and contractile activity has been measured. These preparations also contain a fraction of oriented compounds absorbing at 280 nm and another at 260 nm. During mechanical activity, the amount of oriented compounds increases at 280 nm and decreases at 260 nm. These changes were assigned to an increase in the ratio of oriented amino acids, tyrosine and tryptophan, and to a decrease of oriented adenosine triphosphate.