Distribution and regulation of epithelial cadherin messenger ribonucleic acid and immunocytochemical localization of epithelial cadherin in the rat epididymis.

The epithelium of the epididymis possesses an elaborate network of tight junctions between principal cells which is altered as a function of postnatal age. Cadherins are implicated in the formation of tight junctions. The objective of the present study was to determine whether RNA transcripts for cadherins were present in the epididymis, and if so, how they were hormonally regulated. Using specific cDNA probes for epithelial cadherin (E-Cad) and neural cadherin (N-Cad), Northern blot analysis was used to study steady state levels of cadherin mRNAs. A major E-Cad mRNA species of 4.7 kilobases and a weaker 4.3-kilobase species were observed in the epididymis. No signal for N-Cad was detected. Steady state mRNA levels for E-Cad were highest in the caput and corpus epididymidis and were almost 4 times higher than those in the initial segments and cauda epididymidis; no signal was detected in the vas deferens. Light microscopic immunocytochemical localization of E-Cad revealed a reaction over the principal cells of the entire epididymis. The relative intensities of the immunoreactivity suggested that the E-Cad protein concentration was highest in the corpus, followed by the caput, cauda, and initial segments of the epididymis. There was no reaction over the epithelial basal and clear cells or intraepithelial halo cells. Three days after bilateral orchidectomy, E-cad mRNA was decreased by 75% in the caput epididymidis. A dose-dependent maintenance of mRNA concentration for E-Cad was observed throughout the epididymis of orchidectomized rats after replacement with testosterone. Fourteen days after unilateral orchidectomy, no differences were observed in the concentrations of epididymal E-Cad mRNA between control and unilaterally orchidectomized rats. Together, these data demonstrate that mRNA for E-Cad is present and translated in the rat epididymis, is differentially distributed along this tissue, and can be regulated by circulating androgens.