RT Journal Article
SR Electronic
T1 NNC 55-0396 [(1<em>S</em>,2<em>S</em>)-2-(2-(<em>N</em>-[(3-Benzimidazol-2-yl)propyl]-<em>N</em>-methylamino)ethyl)-6-fluoro-1,2,3,4-tetrahydro-1-isopropyl-2-naphtyl cyclopropanecarboxylate dihydrochloride]: A New Selective Inhibitor of T-Type Calcium Channels
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 193
OP 199
DO 10.1124/jpet.103.060814
VO 309
IS 1
A1 Huang, Luping
A1 Keyser, Brian M.
A1 Tagmose, Tina M.
A1 Hansen, J. Bondo
A1 Taylor, James T.
A1 Zhuang, Hean
A1 Zhang, Min
A1 Ragsdale, David S.
A1 Li, Ming
YR 2004
UL http://jpet.aspetjournals.org/content/309/1/193.abstract
AB Mibefradil is a Ca2+ channel antagonist that inhibits both T-type and high-voltage-activated Ca2+ channels. We previously showed that block of high-voltage-activated channels by mibefradil occurs through the production of an active metabolite by intracellular hydrolysis. In the present study, we modified the structure of mibefradil to develop a nonhydrolyzable analog, (1S, 2S)-2-(2-(N-[(3-benzimidazol-2-yl)propyl]-N-methylamino)ethyl)-6-fluoro-1,2,3,4-tetrahydro-1-isopropyl-2-naphtyl cyclopropanecarboxylate dihydrochloride (NNC 55-0396), that exerts a selective inhibitory effect on T-type channels. The acute IC50 of NNC 55-0396 to block recombinant α1G T-type channels in human embryonic kidney 293 cells was ∼7 μM, whereas 100 μM NNC 55-0396 had no detectable effect on high-voltage-activated channels in INS-1 cells. NNC 55-0396 did not affect the voltage-dependent activation of T-type Ca2+ currents but changed the slope of the steady-state inactivation curve. Block of T-type Ca2+ current was partially relieved by membrane hyperpolarization and enhanced at a high-stimulus frequency. Washing NNC 55-0396 out of the recording chamber did not reverse the T-type Ca2+ current activity, suggesting that the compound dissolves in or passes through the plasma membrane to exert its effect; however, intracellular perfusion of the compound did not block T-type Ca2+ currents, arguing against a cytoplasmic route of action. After incubating cells from an insulin-secreting cell line (INS-1) with NNC 55-0396 for 20 min, mass spectrometry did not detect the mibefradil metabolite that causes L-type Ca2+ channel inhibition. We conclude that NNC 55-0396, by virtue of its modified structure, does not produce the metabolite that causes inhibition of L-type Ca2+ channels, thus rendering it more selective to T-type Ca2+ channels. The American Society for Pharmacology and Experimental Therapeutics