Expression of the L-type calcium channel with two different beta subunits and its modulation by Ro 40-5967.
The smooth muscle alpha 1Cb subunit of the L-type calcium channel was expressed alone (CHO alpha 1 cell) or together with the skeletal beta 1 (CHO alpha 1 beta 1 cell) subunit or smooth muscle beta 3 (CHO alpha 1 beta 3 cell) subunit in Chinese hamster ovary (CHO) cells. The interaction of the expressed calcium channel with the non-dihydropyridine calcium channel blocker Ro 40-5967 was studied. Ro 40-5967 decreased isradipine binding by an apparent allosteric interaction and blocked the barium inward currents (IBa) in a voltage- and use-dependent manner in all cells. The steady-state inactivation curves were shifted to hyperpolarizing potentials in the presence of Ro 40-5967. The rate of channel inactivation was increased in CHO alpha 1 and CHO alpha 1 beta 3 cells. The shift in the steady-state inactivation curve and the increase in channel inactivation were less pronounced in CHO alpha 1 beta 1 cells than in the other cell lines. Low concentrations of Ro 40-5967 increased IBa by up to 198% in 33% of the CHO alpha 1 beta 1 cells. In addition, higher concentrations of Ro 40-5967 were required to inhibit IBa in 60% of the CHO alpha 1 beta 3 cells. These results suggest that the beta subunits modify the interaction of the non-dihydropyridine Ro 40-5967 with the expressed calcium channel alpha 1 subunit.
Welling
A
A
Institut für Pharmakologie und Toxikologie, Technische Universität München, Germany.
Lacinova
L
L
Donatin
K
K
Ludwig
A
A
Bosse
E
E
Flockerzi
V
V
Hofmann
F
F
D000818:Animals; D000911:Antibodies, Monoclonal; D001562:Benzimidazoles / Q000494:pharmacology*; D016466:CHO Cells; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D006224:Cricetinae; D004594:Electrophysiology; D017275:Isradipine / Q000494:pharmacology; D020748:Mibefradil; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D013237:Stereoisomerism; D013764:Tetrahydronaphthalenes / Q000494:pharmacology*; D014162:Transfection; D014700:Verapamil / Q000031:analogs & derivatives / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D001562:Benzimidazoles; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D013764:Tetrahydronaphthalenes; D020748:Mibefradil; D014700:Verapamil; C055885:devapamil; D017275:Isradipine