Expression of aquaporin-4 water channels in rat cholangiocytes

Raúl A. Marinelli, Linh D. Pham, Pamela S. Tietz, Nicholas F La Russo

Research output: Contribution to journalArticle

49 Citations (Scopus)

Abstract

We recently reported that secretin induces the exocytic insertion of functional aquaporin-1 water channels (AQP1) into the apical membrane of cholangiocytes and proposed that this was a key process in ductal bile secretion. Because AQP1 is present on the basolateral cholangiocyte membrane in low amounts, we hypothesized that another AQP must be expressed at this domain to facilitate transbasolateral water movement. Thus, we investigated the expression, subcellular localization, possible regulation by secretin, and functional activity of AQP4, a mercury-insensitive water channel expressed in other fluid transporting epithelia. Using reverse transcription- polymerase chain reaction (RT-PCR) on RNA prepared from purified rat cholangiocytes, we amplified a product of 311 bp that was 100% homologous to the reported AQP4 sequence. RNase protection assay confirmed the presence of an appropriate size transcript for AQP4 in cholangiocytes. Immunoblotting detected a band of approximately 31 kd corresponding to AQP4 in basolateral but not apical membranes of cholangiocytes. Secretin did not alter the amount of plasma membrane AQP4 but, as expected, induced AQP1 redistribution from intracellular to apical plasma membranes. Functional studies showed that AQP4 accounts for about 15% of total cholangiocyte membrane water permeability. Our results indicate that: (1) cholangiocytes express AQP4 messenger RNA (mRNA) and protein and (2) in contrast to AQP1, which is targeted to the apical cholangiocyte membrane by secretin, AQP4 is constitutively expressed on the basolateral cholangiocyte membrane and is secretin unresponsive. The data suggest that AQP4 facilitates the basolateral transport of water in cholangiocytes, a process that could be relevant to ductal bile formation.

Original languageEnglish (US)
Pages (from-to)1313-1317
Number of pages5
JournalHepatology
Volume31
Issue number6
StatePublished - 2000

Fingerprint

Aquaporin 4
Aquaporins
Secretin
Membranes
Bile
Cell Membrane
Aquaporin 1
Water Movements
Water
Ribonucleases
Mercury
Immunoblotting
Reverse Transcription
Permeability
Epithelium
RNA
Polymerase Chain Reaction
Messenger RNA

ASJC Scopus subject areas

  • Hepatology

Cite this

Marinelli, R. A., Pham, L. D., Tietz, P. S., & La Russo, N. F. (2000). Expression of aquaporin-4 water channels in rat cholangiocytes. Hepatology, 31(6), 1313-1317.

Expression of aquaporin-4 water channels in rat cholangiocytes. / Marinelli, Raúl A.; Pham, Linh D.; Tietz, Pamela S.; La Russo, Nicholas F.

In: Hepatology, Vol. 31, No. 6, 2000, p. 1313-1317.

Research output: Contribution to journalArticle

Marinelli, RA, Pham, LD, Tietz, PS & La Russo, NF 2000, 'Expression of aquaporin-4 water channels in rat cholangiocytes', Hepatology, vol. 31, no. 6, pp. 1313-1317.
Marinelli RA, Pham LD, Tietz PS, La Russo NF. Expression of aquaporin-4 water channels in rat cholangiocytes. Hepatology. 2000;31(6):1313-1317.
Marinelli, Raúl A. ; Pham, Linh D. ; Tietz, Pamela S. ; La Russo, Nicholas F. / Expression of aquaporin-4 water channels in rat cholangiocytes. In: Hepatology. 2000 ; Vol. 31, No. 6. pp. 1313-1317.
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