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Abstract
The family of voltage-gated calcium-ion (Ca2+) channels is critical in the role of transmembrane signaling of excitable cells throughout
the body. Within the cardiovascular system, two types of Ca2+ channels have been identified: the L-type channel and the T-type channel. These two
types of Ca2+ channels have distinct electrophysiologic identities, and although the roles of the
T-type Ca2+ channels have not been firmly established, there are many reasons for believing that
the roles of the T-type and L-type Ca2+ channels are distinct. T-type Ca2+ channels have the appropriate characteristics to generate pacemaker activity in the
sinoatrial node. In vascular smooth muscle, they appear to be involved in maintenance
of coronary and peripheral vasomotor tone and control of vascular growth and remodeling.
Characterization of the T-type Ca2+ channels will be facilitated by the availability of mibefradil, a novel calcium antagonist
that selectively blocks T-type Ca2+ channels. Mibefradil is associated with a reduction in heart rate but not with negative
inotropic effects or neurohormonal stimulation. It is thought that the unique pharmacologic
effects of mibefradil are related to blockade of T-type Ca2+ channels, and it is hypothesized that this action will have a positive impact on
cardiovascular morbidity and mortality via cardioprotective and renoprotective effects.
However, much work needs to be done to fully test this hypothesis.
Keywords
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© 1997 Published by Elsevier Inc.
