modulated membrane guanylate cyclase in the testes

To date, the calcium-regulated membrane guanylate cyclase Rod Outer Segment Guanylate Cyclase type 1 (ROS-GC1) transduction system in addition to photoreceptors is known to be expressed in three other types of neuronal cells: in the pinealocytes, mitral cells of the olfactory bulb and the gustatory epithelium of tongue. Very recent studies from our laboratory show that expression of ROS-GC1 is not restricted to the neuronal cells; the male gonads and the spermatozoa also express ROS-GC1. In this presentation, the authors review the existing information on the localization and function of guanylate cyclase with special emphasis on [Ca.sup.2+]-modulated membrane guanylate cyclase, ROS-GC1, in the testes. The role of ROS-GC1 and its [Ca.sup.2+]-sensing modulators in the processes of spermatogenesis and fertilization are discussed. Keywords Testis * Spermatozoa * [Ca.sup.2+]-modulated membrane guanylate cyclase * ROS-GC1