Nitric oxide plays an important role in intercellular signaling, ensuring coordinated
functioning of the urinary bladder during filling and emptying cycles. Inflammation of
the urinary bladder disrupts intercellular signaling, leading to disturbances in the
micturition cycle. The location of endothelial nitric oxide synthase (eNOS) and its
regulation through caveolae in the urinary bladder remains poorly understood. In this
study, we examined the expression and distribution of eNOS and caveolin-1 in the walls
of both normal and inflamed mouse urinary bladders using multiple primary antibodies
on samples prepared through various methods. The normal urinary bladder had a fully
differentiated urothelium, and inducible nitric oxide synthase (iNOS) was not expressed.
Using an antibody that confirmed eNOS expression via Western blot, individual cells in
the lamina propria and endothelial cells were labeled. With one antibody, the reaction
was also positive in the cytoplasm of individual basal cells and beneath the plasma
membrane of intermediate urothelial cells. Caveolin-1 was present on the plasma
membrane of fibroblasts, interstitial and endothelial cells in lamina propria, and smooth
muscle cells of the detrusor. Reliable colocalization of eNOS and caveolin-1 was not
observed. On the first and third days following treatment with cyclophosphamide (150
mg/kg and 300 mg/kg), the urothelium was not fully differentiated, and the expression of
iNOS increased significantly, indicating the presence of inflammation. During
inflammation, eNOS was expressed in the basal cells of the urothelium, and caveolin-1
was present on the plasma membrane of cells, as in the normal urinary bladder but in
lesser amounts. Our results suggest that eNOS is primarily expressed in the endothelium
and individual cells in the lamina propria in both normal and inflamed urinary bladders.
Immunohistochemistry results for eNOS expression depend on the antibodies used and
sample preparation methods. Caveolin-1 is present in the lamina propria and detrusor but
not in the urothelium.
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