Expression of phosphodiesterase 5 (PDE5) in the rat testis at several pre and postnatal developmental stages was investigated by immunohistochemistry. The enzyme was localised in vascular smooth muscle cells, as well as in Leydig and peritubular cells. The latter were identified as myoid, based on their immunoreactivity to desmin and alpha-smooth muscle actin. The presence of PDE5 in myoid cells was confirmed by Western blot analysis and immunohistochemistry performed on highly purified cell fractions, obtained from 16-day-old rats. The expression of PDE5 in these somatic cells of rat testis is discussed in view of the roles played by cGMP signal transduction pathways in the mammalian male reproductive function.

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Calcium calmodulin-dependent cyclic nucleotide phosphodiesterase (PDE1) was identified in crude extract and immunolabeled sections of rat retina. Both cAMP and cGMP PDE activities were stimulated by calcium-calmodulin (4.7-fold and 2.3-fold, respectively). To characterize PDE1 isoforms in retinal cells further, we used antibodies that specifically recognize PDE1 gene products. PDE1B antibody stained a band at molecular mass of 63 kDa whereas PDE1C antibody recognized two bands at 74- and 70-kDa molecular masses. Two PDE1A antibodies (against N-terminal and C-terminal peptides) detected a band at 79 kDa never described before. Immunohistochemical analysis showed a distribution of PDE1A in the outer retina with a bright fluorescence in the outer segments of photoreceptors. PDE1B is uniformly distributed across the retina. PDE1C is confined mainly to the inner retina, with a precise localization in the inner nuclear layer. Immunostaining with choline acetyltransferase antibody indicates localization in cholinergic amacrine cell. The present data provide evidence of expression of PDE1 isoforms in mammalian retina with a complementary distribution of PDE1A and PDE1C, suggesting different roles in retinal function.

Calmodulin-dependent phosphodiesterase (PDE1) is a key enzyme in cyclic nucleotides metabolism. We studied its gene expression and protein localization during retinal development in chick embryos. Western blot and densitometric analysis demonstrated that the expression of the three isoforms changed during development. PDE1A was highly expressed at the early stages and decreased as development proceeded. PDE1B expression remained relatively low and constant over time. PDE1C showed a prominent increase (13-fold) between embryonic day (E) 7 and E13, followed by a moderate increase between E13 and postnatal day (P) 1. The presence of the enzyme in the different retinal locations was strongly modulated by development. PDE1A immunostaining was first detected at the ganglion cell level (E7), then in the outer retina (E15-E21). At P5, the immunostaining was confined in the optic fiber layer. Isoform C immunolocalization followed the same inner-outer pattern as isoform A. At 5 days posthatching (P5), the immunoreactivity was restricted, as well as for the isoform A, in the optic fiber layer. The isoform B immunolabelling was low and evenly distributed across the retina at all stages. The different developmental profiles of PDE1A, PDE1B, and PDE1C induced a temporal modulation in cyclic nucleotides concentration, suggesting specific roles of this enzyme in the morphofunctional development of retinal circuitry.