No expression was detected in ureteric buds and other early developing structures, such as comma bodies, S shaped bodies, glomeruli, etc. It has previously been established that Bcl-2 and Bax are involved in the regulation of apoptosis, as well as in mitochondrial fusion and fission. Since the amount of mitochondria is similar in proximal and distal tubules, the difference in expression of Bcl-2 and Bax might be attributable to functional differences between proximal and distal tubule mitochondria. This view is supported by a recent study, which revealed functional differences between mitochondria from proximal and distal tubule cells. These differences were mainly observed in mitochondrial membrane potential, the expression ratio of ATPase and its inhibitor, the product of reactive oxygen species, and glutathione levels. Furthermore, mitochondrial glycolysis differs between proximal and distal tubule cells, and between proximal convoluted and straight tubule cells. This is supported by the findings of a series of in vitro studies, which show that the glycolysis in the S3 segment of the proximal tubule is less pronounced than in the distal tubules. All these functional differences between proximal and distal tubule mitochondria may explain why the proximal tubule is more vulnerable to ischemic, hypoxic, and toxic injury in adulthood than the distal tubule. Thus, damage to the distal tubule is only observed after severe renal ischemia reperfusion injury. It has previously been suggested that Bcl-2 and Bax plays a pivotal role in inducing mitochondria mediated Cefetamet pivoxil HCl apoptosis in glomerular diseases and ischemic and toxic kidney injury. Therefore, it is interesting that we found that Bcl-2 and Bax were mainly co-expressed in mature proximal convoluted tubules. If such an ischemia initiates an apoptotic response and if the tissue damage continues after the circulation has been reestablished, then it might be possible to reduce tissue damage by interacting with the Bcl-2 and Bax apoptosis regulating Imperatorin activity. However, at present it is too early to suggest the existence of such a treatment of acute renal failure.