Endothelin and endothelin receptors A and B in the human testis

Human testicular capillaries interconnect Leydig cells and seminiferous tub ules. Microcirculation and blood flow are therefore essential for the maint enance of spermatogenesis. The expression and the localisation of ET (endot helin) and its receptors in testicular tissue, in seminiferous tubules and in human testicular capillaries were studied. ET-1 mRNA was detected in who le testicular tissue and in seminiferous tubules whereas isolated testicula r capillaries were negative. Big ET-1 (Big endothelin 1) and ET peptides we re localised in Leydig and Sertoli cells whereas interstitial and intramura l capillaries (within the lamina propria) remained unstained. ET was also f ound in mature spermatids. ET-A (endothelin receptor A) mRNA was detected i n seminiferous tubules and whole testicular tissue whereas testicular blood vessels were negative. ET-A immunostaining was displayed in Leydig and Ser toli cells and in spermatids. ET-B (endothelin receptor B) mRNA was detecte d in whole testicular tissue, seminiferous tubules and in testicular capill aries. ET-B peptide was prominent in Leydig cells, peritubular cells, endot helial cells and pericytes of interstitial and intramural capillaries as we ll as in vascular endothelial and smooth muscle cells. From these results w e conclude that ET produced in Leydig and Sertoli cells can act in a paracr ine manner via ET-B on the human testicular microvasculature and the peritu bular cells. The presence of both ET-A and ET-B in Leydig cells and of ET-A in Sertoli cells leads to the assumption that ET could influence these cel ls as an autocrine factor.