PMID- 10392550
OWN - NLM
STAT- MEDLINE
DCOM- 19990810
LR  - 20190822
IS  - 0378-5955 (Print)
IS  - 0378-5955 (Linking)
VI  - 132
IP  - 1-2
DP  - 1999 Jun
TI  - Expression pattern of aquaporin water channels in the inner ear of the rat. The
      molecular basis for a water regulation system in the endolymphatic sac.
PG  - 76-84
AB  - Mammalian aquaporins constitute a family of so far 10 related water channel
      proteins which mediate osmotically driven water fluxes across the plasma
      membrane. Because regulation of the ionic composition and osmolality of inner ear
      fluids is of great functional significance, we investigated the expression
      patterns of aquaporins in five defined areas of the rat inner ear by RT-PCR. The 
      tissues used were stria vascularis, endolymphatic sac, Reissner's membrane,
      vestibulum and organ of Corti. Aquaporin 1 transcripts were detected in all
      tissues and are probably constitutive. Aquaporin 5 was only expressed in the
      organ of Corti and in Reissner's membrane. We show that aquaporin 2, so far
      considered to be specific to the principal cells of the renal collecting duct, is
      expressed in the endolymphatic sac. Aquaporin 2 expression was not detected in
      any other inner ear region. The postnatal appearance of aquaporin 2 transcripts
      in the endolymphatic sac resembled that in the kidney, i.e. it increased
      postnatally until day 4. The full-length DNA for aquaporin 2 was cloned from cDNA
      of the endolymphatic sac. It had an irrelevant Ile54Thr mutation because it could
      be functionally expressed in Xenopus oocytes. Also exclusively in the
      endolymphatic sac of the inner ear, we detected transcripts for aquaporin
      isoforms 3 and 4 which are known to be expressed in the renal principal cells. In
      the kidney, aquaporin 2 regulation involves vasopressin-stimulated,
      cAMP-dependent phosphorylation of Ser256 of aquaporin 2 which is stored in
      cytosolic vesicles. These storage vesicles also contain a serpentine
      calcium/polycation-sensing receptor. Vesicle shuffling to the plasma membrane
      involves proteins such as vesicle-associated membrane protein VAMP2, syntaxin-4
      and the small GTPase Rab3a. Using RT-PCR we were able to demonstrate the
      expression of all of these components. By analogy the data suggest that in the
      endolymphatic sac of the inner ear a system for cellular water permeability is in
      place which may share many similarities with that characterized in the principal 
      cells of the renal collecting duct. These findings may have a number of
      interesting pharmacological implications which need to be addressed in future
      studies.
FAU - Beitz, E
AU  - Beitz E
AD  - Faculty of Chemistry and Pharmacy, University of Tubingen, Germany.
FAU - Kumagami, H
AU  - Kumagami H
FAU - Krippeit-Drews, P
AU  - Krippeit-Drews P
FAU - Ruppersberg, J P
AU  - Ruppersberg JP
FAU - Schultz, J E
AU  - Schultz JE
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - Netherlands
TA  - Hear Res
JT  - Hearing research
JID - 7900445
RN  - 0 (Aqp2 protein, rat)
RN  - 0 (Aquaporin 2)
RN  - 0 (Aquaporin 6)
RN  - 0 (Aquaporins)
RN  - 0 (Protein Isoforms)
RN  - 0 (RNA, Messenger)
SB  - IM
MH  - Aging/metabolism
MH  - Amino Acid Sequence/genetics
MH  - Animals
MH  - Animals, Newborn/growth & development/metabolism
MH  - Aquaporin 2
MH  - Aquaporin 6
MH  - Aquaporins/genetics/*metabolism
MH  - Body Water/*metabolism
MH  - Ear, Inner/*metabolism
MH  - Endolymphatic Sac/*metabolism
MH  - Molecular Sequence Data
MH  - Protein Isoforms/metabolism
MH  - RNA, Messenger/metabolism
MH  - Rats
EDAT- 1999/07/07 00:00
MHDA- 1999/07/07 00:01
CRDT- 1999/07/07 00:00
PHST- 1999/07/07 00:00 [pubmed]
PHST- 1999/07/07 00:01 [medline]
PHST- 1999/07/07 00:00 [entrez]
AID - S0378-5955(99)00036-2 [pii]
AID - 10.1016/s0378-5955(99)00036-2 [doi]
PST - ppublish
SO  - Hear Res. 1999 Jun;132(1-2):76-84. doi: 10.1016/s0378-5955(99)00036-2.