The inhibition of receptor-mediated and voltage-dependent calcium entry by the antiproliferative L-651,582

• Published in: The Journal of biological chemistry Vol. 266; no. 16; pp. 10136 - 10142
• Main Authors: HUPE, D. J, BOLTZ, R, COHEN, C. J, FELIX, J, HAM, E, MILLER, D, SODERMAN, D, VAN SKIVER, D
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Biochemistry and Molecular Biology 05.06.1991
• Subjects: Aminoimidazole Carboxamide - analogs & derivatives; Aminoimidazole Carboxamide - pharmacology; Animals; Antibiotics. Antiinfectious agents. Antiparasitic agents; Antineoplastic Agents - pharmacology; Antiparasitic agents; Arachidonic Acids - metabolism; Biological and medical sciences; calcium; Calcium - antagonists & inhibitors; Calcium Channels - drug effects; Guinea Pigs; Heart Atria - cytology; Heart Atria - drug effects; Heart Atria - metabolism; Ion Channel Gating - drug effects; leukocytes (polymorphonuclear); Medical sciences; N-Formylmethionine Leucyl-Phenylalanine - metabolism; Neutrophils - metabolism; Pharmacology. Drug treatments; Rats; Triazoles; Cell proliferation; Cell culture; Calcium; Rat; Rodentia; Granulocyte; Ion transport; Ionic channel; Metabolism; Fatty acids; In vitro; Vertebrata; Membrane receptor; Mammalia; Neutrophile; Animal; Parasiticid; Mechanism of action; Tumor cell
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)99200-8

L-651,582, 5-amino-[4-(4-chlorobenzoyl)-3,5-dichlorobenzyl]-1,2,3-triazole-4- carboxamide, an antiproliferative and antiparasitic agent previously shown to affect 45Ca2+ uptake into mammalian cells, inhibits both receptor-mediated and voltage-dependent calcium entry in well characterized in vitro systems. Indo 1 fluorescence measurements of cytosolic calcium levels indicate that the drug has no effect on the initial transient release of internal stores of calcium stimulated by fMet-Leu-Phe in rat polymorphonuclear leukocytes. It does decrease the levels maintained subsequently, however, indicating blockage of calcium influx through receptor-operated channels. L-651,582 also blocks the stimulation of leukotriene B4 (LTB4) production by fMet-Leu-Phe with an IC50 = 0.5 micrograms/ml equal to that for calcium entry inhibition. The LTB4 inhibition is likely due to calcium entry inhibition since L-651,582 does not inhibit calmodulin or enzymes producing arachidonate metabolites. L-651,582 also inhibits potassium-stimulated 45Ca2+ influx into GH3 cells with an IC50 of 0.5 microgram/ml, indicating a block of voltage-gated L-type calcium channels. Patch voltage clamp measurements of current through L- and T-type calcium in guinea pig atrial cells also indicate that L-651,582 is a calcium antagonist. Block of L-type calcium channels is voltage-dependent, and the apparent dissociation constant for the high affinity state is 0.2 micrograms/ml. The IC50 for block of T-type calcium channels is 1.4 micrograms/ml. The inhibition of cellular proliferation and the production of arachidonate metabolites by L-651,582 may be the result of the nearly equipotent block of receptor-operated and voltage-gated calcium channels.