Immunohistochemical Localization of the Water Channels AQP4 and AQP5 in the Rat Pituitary Gland

Toshiyuki Matsuzaki
Yuki Inahata
Nobuhiko Sawai
Chun-Ying Yang
Makito Kobayashi
Kuniaki Takata
Hitoshi Ozawa

The pituitary gland is composed of the adenohypophysis and neurohypophysis. The adenohypophysis contains endocrine cells
 folliculo-stellate (FS) cells
 and marginal layer cells
 whereas the neurohypophysis mainly comprises axons and pituicytes. To understand the molecular nature of water transfer in the pituitary gland
 we examined the immunohistochemical localization of the membrane water channels aquaporin-4 (AQP4) and AQP5 in rat tissue. Double immunofluorescence analysis of AQP4 and S100 protein
 a known marker for FS cells
 marginal layer cells
 and pituicytes
 clearly revealed that FS cells and marginal layer cells in the adenohypophysis and the pituicytes in pars nervosa are positive for AQP4. AQP5 was found to be localized at the apical membrane in some marginal layer cells surrounding the Rathke's residual pouch
 in which AQP4 was observed to be localized on the basolateral membranes. These results suggest the following possibilities: 1) FS cells especially require water for their functions and 2) transepithelial water transfer could occur between the lumen of Rathke's residual pouch and the interstitial fluid in the adenohypophysis through the AQP4 and AQP5 channels in the marginal layer cells.

ACTA HISTOCHEMICA ET CYTOCHEMICA

JAPAN SOC HISTOCHEMISTRY & CYTOCHEMISTRY

44

6

10.1267/ahc.11031

https://doi.org/10.1267/ahc.11031
https://www.ncbi.nlm.nih.gov/pubmed/22282586
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