The density and distribution of endothelin 1 and endothelin receptor subtypes in normal and diabetic rat corpus cavernosum

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Abstract
Objective To investigate the density and distribution of endothelin l(ET‐l) and endothelin receptor subtypes in rat cavernosal tissue, and to assess any changes brought about by the onset of diabetes mellitus (DM).Materials and methods Hyperglycaemic non‐ketotic diabetes mellitus was induced in five rats using streptozo‐tocin (STZ). Two months later the penises were excised and stored at—70°C. Longitudinal serial sections (6 μm) were cut using a cryostat and thaw‐mounted onto gelatinized microscope slides. Low and high resolution autoradiographs were taken using radioligands for ET‐1 and endothelin A (ETA) and endothelin B (ETB) receptors and the autoradiographs analysed densitometrically. These results were compared with those from five age‐matched control rats.Results ET‐1 and ETA receptor binding was primarily localized to the endothelium lining the cavernosal lacunar spaces; trabecular corporeal smooth muscle was much less intensely stained. No ETB receptor binding could be demonstrated, but increased binding of ET‐1 and ETA receptors was seen in the diabetic cavernosal tissue.Conclusion ET‐1 and ETA receptor binding is increased in diabetic rat cavernosal tissue. A reduction in receptor linked nitric oxide (NO) release has previously been reported in diabetic rats. This finding may provide an explanation for the upregulation of ET‐1 and ETA receptor binding in the diabetic rat.