Expression of the water-channel protein aquaporin 4 in the H-Tx rat: possible compensatory role in spontaneously arrested hydrocephalus.
OBJECTIVE
Aquaporin (AQP) water channels play an important role in water movement in the central nervous system. The authors used an animal model to examine the relationship between AQP4 expression and spontaneously arrested hydrocephalus.


METHODS
. Congenitally hydrocephalic H-Tx (hH-Tx) rats and nonhydrocephalic H-Tx (nH-Tx) rats were used in the study. Brain tissue sections were obtained from animals in both groups at 1 day, 1 week, 4 weeks, and 8 weeks of age. Sections were immunostained using AQP4 antibodies, and AQP4 expression was assessed. In the nH-Tx group, no AQP4 expression was seen in 1-day-old rats, and AQP4 expression was found in astrocytes around capillaries of the cerebral cortex and in ependymal cells lining the ventricles in 1-week-old rats. In the 4- and 8-week-old nH-Tx animals, AQP4 expression was seen in subpial zones of the cortex, on foot processes of pericapillary astrocytes, and in periventricular regions. A marked increase in cerebral cortical expression of AQP4 was observed at 8 weeks in the hH-Tx rats but not in the nH-Tx rats.


CONCLUSIONS
The authors hypothesize that the differences in cerebral AQP4 expression in the 1-day-old and 1-week-old nH-Tx rats compared with the 4- and 8-week-old nH-Tx rats may be related to the fact that the cerebrospinal fluid (CSF) circulation of newborns and infants differs from that of adults. It is also possible that the increased expression of AQP4 seen in the 8-week-old hH-Tx animals was related to the development of alternative pathways of CSF circulation, which also may occur in instances of spontaneously arrested hydrocephalus.
Shen
Xi Qing
XQ
Department of Neurosurgery and Research Institute for Diseases of Old Age, Juntendo University School of Medicine, Tokyo, Japan.
Miyajima
Masakazu
M
Ogino
Ikuko
I
Arai
Hajime
H
D000367:Age Factors; D000818:Animals; D051401:Aquaporin 4 / Q000235:genetics* / Q000378:metabolism*; D002555:Cerebrospinal Fluid / Q000378:metabolism*; D004195:Disease Models, Animal; D015870:Gene Expression / Q000502:physiology; D006849:Hydrocephalus / Q000378:metabolism* / Q000503:physiopathology*; D007150:Immunohistochemistry; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011922:Rats, Mutant Strains; D012075:Remission, Spontaneous; D014867:Water / Q000378:metabolism
C496032:Aqp4 protein, rat; D051401:Aquaporin 4; D012333:RNA, Messenger; D014867:Water