Spatiotemporal Regulation of the Two Atrial Natriuretic Peptide Receptors in Testis

By interacting with a guanylyl cyclase (GC) activity-containing receptor, termed GCp-A, atrial natriuretic peptide (ANP) acts as a regulator of blood pressure and fluid volume homeostasis. High expression levels of GC-A in the testis and reported effects of ANP on testosterone secretion by Leydig cells are indicative of important local functions in this organ. Here we show, based on radioligand receptor labeling and immunological approaches, that seminiferous tubules rather than Leydig cells are the predominant GC-A expression sites in the rat testis. Functional activity was proved by ANP-induced cGMP accumulation in isolated seminiferous tubules. Although ontogenetic studies revealed a massive increase in GC-A levels during sexual maturation, the so-called natriuretic peptide clearance receptor, another type of ANP receptor proposed to locally control the availability of natriuretic peptides, was found to be expressed predominantly before puberty, exceeding the level of GC-A expression at this time. Natriuretic peptide clearance receptor also shows a distinct distribution pattern surrounding the seminiferous tubules. These findings raise the possibility of novel physiological roles for ANP and cGMP in the testis related to germ cell maturation and/or the regulation of the onset of puberty and suggest that the two ANP receptors function in a coordinated manner at this target organ.