Distribution of phosphodiesterase type 5 (PDE5) in the lateral wall of the guinea pig urinary bladder

Objective To study PDE5 localisation by visualising the product of phosphodiesterase type 5 (PDE5) inhibition, namely cGMP, to determine the site of action of inhibitors in the urinary bladder. Materials and Methods Bladders of nine male guinea pigs were dissected and treated in wells containing 2mL Krebs' solution and 1M of the specific PDE5 inhibitor vardenafil at 36 degrees C for 30min. After stimulating tissues with 100M of the nitric oxide (NO) donor diethylamine-NONOate for 10min, the tissues were snap-frozen and 9-10m sections were cut. Sections were examined for cGMP immunoreactivity and also stained for vimentin, a marker for interstitial cells and the neuromarkers protein gene product 9.5 (PGP9.5), synaptic vesicle protein 2 (SV2), neurofilament (NF) and calcitonin gene-related peptide (CGRP), using the two-step indirect immunohistochemistry technique. Results After PDE5 inhibition, cGMP was found to be present in the urothelium, suburothelial interstitial cells and endothelium of blood vessels. cGMP was not expressed in nerves positive for CGRP, NF and SV2, and was expressed only in very few efferent nerves positive for PGP9.5. Conclusion Our data show that the possible sites of action of PDE5 inhibition in the bladder are the urothelium, suburothelial interstitial cells and blood vessels, rather than the bladder nerve fibres.