Characterization and localization of nitric oxide synthase isoforms in the BB/WOR diabetic rat

Erectile dysfunction is a common pathological development in individuals with diabetes mellitus. Nitric oxide synthase (NOS) is essential for regulation of normal penile erection and NOS protein activity has been shown to be altered with diabetes. Several different isoforms and subtypes of NOS exist. However, little is known about how the distribution and abundance of these isoforms are altered with diabetes. We characterized the distribution and abundance of NOS isoforms and explored how they are altered with diabetes and result in erectile failure.

In situ hybridization and quantitative reverse transcriptase-polymerase chain reaction were done to measure the abundance and distribution of NOS-Ia, NOS-Ib, NOS-Ic, NOS-II and NOS-III in control and diabetic (BB/WOR) rats. Protein was localized by immunohistochemical analysis and alterations in protein abundance with diabetes were examined by Western blot analysis.

NOS-I, NOS-II and NOS-III were observed in the endothelium lining the cavernous spaces and in the epithelium of the urethra. NOS-I protein was also present in the nerves of control and diabetic penes. We observed an increase in NOS-II expression around the dorsal nerves of diabetic penes, a decrease in NOS-III expression in diabetic pelvic ganglia and a decrease in NOS-Ib expression in the diabetic penis. NOS-I protein abundance was significantly decreased in diabetic pelvic ganglia.

To our knowledge this is the first report of regional differences in the distribution of NOS-III in the urethra and altered NOS-Ib gene expression with diabetes.