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Dual effects of G‐protein activation on Ca‐dependent exocytosis in bovine lactotrophs
Author(s) -
Sikdar S.K.,
Zorec R.,
Brown D.,
Mason W.T.
Publication year - 1989
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(89)80936-6
Subject(s) - exocytosis , chemistry , granule (geology) , gtp' , g protein , intracellular , microbiology and biotechnology , endocytosis , biophysics , secretion , biochemistry , biology , cell , receptor , enzyme , paleontology
The whole‐cell patch‐clamp technique was used to measure cell membrane capacitance ( C m ) to monitor exocytosis in single‐cultured bovine prolactin‐secreting cells (lactotrophs) of the anterior pituitary. The cells were dialyzed with solutions containing different concentrations of ionised Ca and non‐hydrolyzable GTP analogues (GTP‐γ‐S and GMP‐PNP) to activate G‐proteins. We have identified two distinct effects of G‐protein activation on Ca‐induced exocytosis: (i) the maximum C m increase due to intracellular Ca‐dependent exocytosis was diminished, suggesting an inhibitory role of G‐proteins close to the site of granule fusion, while (ii) the rate of C m increase (Δ C m /Δ t ) was facilitated, revealing conversely a stimulatory role of G‐proteins in the translocation of secretory granules to the fusion sites.