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Regulation of L‐type Ca 2+ channels in rabbit portal vein by G protein α s and βγ subunits
Author(s) -
Zhong Juming,
Dessauer Carmen W.,
Keef Kathleen D.,
Hume Joseph R.
Publication year - 1999
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.1469-7793.1999.0109z.x
Subject(s) - portal vein , rabbit (cipher) , chemistry , protein subunit , biophysics , microbiology and biotechnology , anatomy , biology , medicine , biochemistry , mathematics , gene , statistics
1 The effect of purified G protein subunits α s and βγ on L‐type Ca 2+ channels in vascular smooth muscle and the possible pathways involved were investigated using freshly isolated smooth muscle cells from rabbit portal vein and the whole‐cell patch clamp technique. 2 Cells dialysed with either Gα s or Gβγ exhibited significant increases in peak Ba 2+ current ( I Ba ) density (148 % and 131 %, respectively) compared with control cells. The combination of Gα s and Gβγ further increased peak I Ba density (181 %). Inactive Gα s and Gβγ did not have any effect on Ca 2+ channels. 3 The stimulatory effect of Gα s on peak I Ba was entirely abolished by the protein kinase A inhibitor Rp‐8‐Br‐cAMPS, or the adenylyl cyclase inhibitor SQ 22536. On the other hand, the stimulatory response of Ca 2+ channels to Gβγ was not affected by the protein kinase A inhibitors Rp‐8‐Br‐cAMPS and KT 5720, or by the Ca 2+ ‐dependent protein kinase C inhibitor bisindolylmaleimide 1, but was completely blocked by the protein kinase C inhibitor calphostin C. Pretreatment of cells with phorbol 12‐myristate 13‐acetate for over 18 h prevented the stimulatory effect of Gβγ on peak I Ba . In addition, acute application of phorbol 12,13‐dibutyrate enhanced peak I Ba density in control cells, which could be entirely blocked by calphostin C. 4 These data indicate that enhancement of Ba 2+ currents by Gα s and Gβγ can be attributed to increased activity of protein kinase A and protein kinase C, respectively. No direct membrane‐delimited pathway for Ca 2+ channel regulation by activated G s proteins could be detected in vascular smooth muscle cells.