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

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.