CYTOCHEMICAL-LOCALIZATION OF GUANYLATE-CYCLASE IN PHOTORECEPTOR CELLSOF THE MOUSE

Background: Light-stimulated excitation causes a decrease of the cGMP concentration in vertebrate photoreceptor cells. The cGMP content is r estored by the catalytic action of a guanylate cyclase (EC 4.6.1.2). M ethods: The spatial distribution of guanylate cyclase was determined c ytochemically in rod visual cells of the mouse. Results: In retinal ti ssue of the mouse guanylate cyclase was found throughout the photorece ptor cells, in the outer and the inner segments, and was especially pr ominent in the cilia and in elongations of cilia extending into the ou ter segments. A reaction product of adenylate cyclase (EC 4.6.1.1) cou ld not be demonstrated in vertebrate rod outer segments. Conclusion: T he relatively high amount of guanylate cyclase in the inner segments a nd the cilia may contribute - at least in part - to the actual concent ration and the time course of concentration changes of the cGMP concen tration in rod outer segments.