Cytochemical localization of guanylate cyclase in photoreceptor cells of the mouse

Background: Light-stimulated excitation causes a decrease of the cGMP concentration in vertebrate photoreceptor cells. The cGMP content is restored by the catalytic action of a guanylate cyclase (EC 4.6.1.2). Methods: The spatial distribution of guanylate cyclase was determined cytochemically in rod visual cells of the mouse. Results: In retinal tissue of the mouse guanylate cyclase was found throughout the photoreceptor cells, in the outer and the inner segments, and was especially prominent in the cilia and in elongations of cilia extending into the outer segments. A reaction product of adenylate cyclase (EC 4.6.1.1) could not be demonstrated in vertebrate rod outer segments. Conclusion: The relatively high amount of guanylate cyclase in the inner segments and the cilia may contribute - at least in part - to the actual concentration and the time course of concentration changes of the cGMP concentration in rod outer segments.