Considering increasing water absorption along the epididymal duct , the bFGF level in the epididymal lumen would be increased from the initial segment to the cauda. However, in the present study the bFGF protein level appeared to remain unchanged in the lumen from the proximal epididymal region to the distal epididymal region (Fig. 10A). An explanation for this result is that the luminal bFGF-like protein could have been reabsorbed from the initial segment to the caput and from caput to cauda via a receptor-mediated endocytosis pathway. Evidence to support this includes the presence of a bFGF receptor in the initial segment (unpublished results) and the increasing level of the 43-kDa bFGF-like protein in the homogenate from the initial segment to the cauda (Fig. 10B). Another possibility is that the 43-kDa bFGF-like protein could be hydrolyzed and degraded by proteases within the epididymal duct, resulting in the decrease of this protein in the lumen from the initial segment to the cauda. asthma inhalers
As discussed earlier, the decreased GGT catalytic activity and GGT protein level (Figs. 1 and 2) could be due to the decreased expression of GGT mRNA-IV in the initial segment following EDL . Our results showed that testicular factors such as bFGF recovered the decreased GGT catalytic activity and GGT protein level (Figs. 3-6) and that bFGF-like proteins were present in the rRTF and luminal fluid from the initial segment (Figs. 9 and 10). It seems possible that bFGF is among the testicular factors involved in regulation of the expression of GGT mRNA-IV in the initial segment. A previous study in this laboratory has shown that like GGT mRNA-IV, an ets transcriptional factor, PEA3, is also highly expressed in the initial segment and is under the regulation of testicular factors.