Expression and Distribution of Aquaporin-2, -3 and -4 in Developing Rat Kidney

Kim, Joon Yong; Shim, Bong Suk; Kim, Jin

Abstract

PURPOSE: The aquaporins (AQPs) are transmembrane water channel proteins. It is well known that AQP2, -3 and -4 contribute to the urinary concentration in collecting duct (CD) and also reported the presence of these three AQPs in the connecting tubule (CNT). Newborn rats are not capable of producing a concentrated urine. Rats develop the ability to concentrate urine after birth. The purpose of this study was to establish the time of the expression and the distribution of AQP2, -3 and -4 in the developing rat kidney.
MATERIALS AND METHODS
Sprague-Dawley rats were used in all experiments. Kidneys were obtained from 16, 18 and 20-day-old fetuses and 1, 4, 7, 14 and 21-day-old pups and preserved and processed for immunohistochemical studies using a preembedding immunoperoxidase procedure. AQP2, -3 and -4 immunoreactivity was detected using rabbit polyclonal antibody and donkey anti-rabbit IgG.
RESULTS
AQP2, -3 and -4 appeared first in 16-day-old fetuses in the CD and in 18-day-old fetuses in the CNT. Immunoreactivity for AQP2, -3 and -4 was markedly increased after birth and gradually increased during development. In CNT cells and principal cells, AQP2, -3 and -4 were not distinctly demonstrated on the apical, lateral and basal plasma membrane respectively until 21 days after birth. Distinct polarity of these AQPs both in CNTcells and principal cells were observed at 21 days after birth.
CONCLUSIONS
AQP2 -3, and -4 were expressed not only in CD but also in CNT before developing of urine concentrating ability during development and it is concluded that their expression and distribution in CNT may play a role in the development of urine concentration abilities in rat kidney.