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 1(ET-1) 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 streptozotocin (STZ). Two months later the penises were excised and stored at -70 degrees C. Longitudinal serial sections (6 mu m) 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.