both adult and in foetal ovaries (Figure 5a,b). The interstitial cells of the adult testicle were strongly positive for Tβ4 while, in the foetus, the same cells showed a mild immunoreactivi- ty for the peptide (Figure 6a,b). Moreover, a mild reactivity of Tβ4 was observed in the sper- matic ducts of the adult testicle (Figure 6b). Discussion This is the first comprehensive study that analyzes Tβ4 presence in the human genitouri- nary tract, and compares the presence of this peptide during development with its reactivity in the adult. We convincingly demonstrate that Tβ4 presence is particular for every organ and, inside each organ, it appears restricted to cer- tain structures or to particular cell types. Many studies in experimental animals and recently in humans suggest that Tβ4 could play a rele- vant role during development.9,23 Our data con- firms this hypothesis. In this study, we find that Tβ4 is present during intrauterine life even in the genitourinary tract, and reveal that immunoreactivity for this peptide may change during postnatal life with marked differences between foetal and adult organs. Our previous studies on Tβ4 protein presence in salivary glands9 and in the gastrointestinal tract23 first disclosed the uneven distribution of the pep- tide in different organs of the same system and within each organ in the different epithelial and mesenchymal structures and cells. Moreover, in recent years, Tβ4 presence has been reported to increase in different tumors,24-26 mainly in its infiltrative borders and in their metastastic stage (Nemolato et al, unpublished data). The uneven distribution of Tβ4 among different organs as well as among different cell types within each organ is con- firmed by this study also in the genitourinary tract. Tβ4 was clearly present in all organs examined in this study; it was more diffuse in kidney, adult bladder and in interstitial cells of the testis. Interestingly, we found differences in this study between foetal and mature organs. In general, we found direct associations between presence of Tβ4 and the degree of development in all the organs tested. The presence of a rela- tionship between Tβ4 presence and the devel- Original paper opmental status does not coincide with our previous data regarding the gastrointestinal tract.23 In previous studies, Tβ4 presence pat- terns were characterized by a higher presence in the foetus and by a marked decrease in the adult suggesting a major role of Tβ4 during embryogenesis. This hypothesis was con- firmed by our studies of Tβ4 content in human saliva,9 which clearly showed high Tβ4 levels during gestation followed by the disappear- ance of the peptide in the adult saliva. Our study reinforces our hypothesis that Tβ4 func- tions are not totally known and stresses the different function this peptide could play in different human organs, not only during devel- opment, but also even during adult life. Some peculiar features related to the patchy Tβ4 dis- tribution in different organs deserve to be noted in: i) kidney restriction of Tβ4 reactivity to ducts and tubules with completely spared glomeruli (Figure 1a,b); ii) a positivity in the oocytes of the ovary (Figure 5a,b); iii) immunoreactivity restricted to interstitial cells in the testis (Figure 6a,b). What is the rela- tionship between these very different types of cells? For the time being, we have no clear answer. The immunoreactivity of oocytes of Figure 4. Prostate. (a) Foetuses: no immu- noreactivity of Tβ4 is observed in the prostate glands and in the surrounding stroma. Scale bar: 50 μm. (b) Adults: no significant immuoreactivity of Tβ4 is detected in the prostate glands. The sur- rounding stroma shows a diffuse immunoreactivity for the peptide (arrow- head). Scale bar: 50 μm. Inset: at higher magnification, no significant immunoreac- tivity for Tβ4 is observed in the prostate gland. Scale bar: 25 μm. Figure 5. Ovary. (a) Foetuses: scattered Tβ4 reactive fine granules are present in the cytoplasm of the oocyte (arrow). A weak diffuse immunoreactivity of the sur- rounding stroma is detected. Scale bar: 25 μm. (b) Adults: a weak and homogeneous cytoplasmic immunoreactivity for Tβ4 is detected in the oocyte of the primary fol- licle (arrow). A weak diffuse immunopos- itivity in the surrounding stroma is observed. Scale bar: 25 μm. Figure 6. Testicle. (a) Foetuses: no immuno- reactivity for Tβ4 is observed in the imma- ture spermatic ducts (arrow). A mild cyto- plasmic immunoreactivity of the peptide is observed in isolated interstitial cells (arrow- head). Scale bar: 25 μm. (b) Adults: a granu- lar cytoplasmic immunoreactivity of Tβ4 is detected in the interstitial cells of the testicle (arrow). A weak immunoreactivity is obser - ved in the cells of the spermatic ducts (arrow- head). Scale bar: 50 μm Inset: cells of the spermatic ducts with a weak immunoreactiv- ity (arrows). Scale bar: 25 μm. [European Journal of Histochemistry 2010; 54:e43] [page 203]