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Tamoxifen and ATP synergistically activate Cl − release by cultured bovine pigmented ciliary epithelial cells
Author(s) -
Mitchell Claire H.,
PetersonYantorno Kim,
CocaPrados Miguel,
Civan Mortimer M.
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.00183.x
Subject(s) - tamoxifen , chemistry , carbachol , calphostin c , secretion , adenosine triphosphate , medicine , endocrinology , adenosine , microbiology and biotechnology , protein kinase c , biology , receptor , kinase , biochemistry , cancer , breast cancer
1 Purines alter aqueous humour secretion by the bilayered ciliary epithelium. Adenosine but not ATP shrinks non‐pigmented ciliary epithelial (NPE) cells by activating Cl − channels. We now report effects of ATP on pigmented ciliary epithelial (PE) cells. 2 Cultured bovine PE cells were studied volumetrically by electronic cell sorting. ATP and tamoxifen acted synergistically to shrink PE cells. Neither ATP nor tamoxifen alone had a consistent effect on cell volume. 3 The tamoxifen, ATP‐activated shrinkage required Cl − release since the response was blocked by removing Cl − and was inhibited by the Cl − channel blockers 5‐nitro‐2‐(3‐phenylpropylamino)‐benzoate and 4,4′‐diisothiocyano‐2,2′‐disulfonic acid. 4 The modulating effect of tamoxifen could have reflected many actions of tamoxifen. Our data do not support the suggestion that tamoxifen inhibits protein kinase C (PKC) or calcium‐calmodulin, or that it acts on histamine or carbachol receptors. 5 The shrinkage produced by ATP and tamoxifen was blocked by 17β‐oestradiol, but not 17α‐oestradiol. 6 The cooperative interaction between tamoxifen and ATP was not mediated by an enhanced rise in [Ca 2+ ] i . 7 The results indicate that tamoxifen interacts synergistically with ATP to activate Cl − release by the PE cells.