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Effects of methylmercury on human neuronal L-type calcium channels transiently expressed in human embryonic kidney cells (HEK-293).
J Pharmacol Exp Ther. 2002 Aug; 302(2):424-32.JP

Abstract

Methylmercury (MeHg) disrupts the function of native, high voltage-activated neuronal Ca(2+) channels in several types of cells. However, the effects of MeHg on isolated Ca(2+) channel phenotypes have not been examined. The aim of the present study was to examine the action of MeHg on recombinant, neuronal L-type voltage-sensitive Ca(2+) channels. Human embryonic kidney cells (HEK-293) were transfected with human neuronal cDNA clones of the alpha(1C-1) subunit in combination with alpha(2b) and beta(3a) Ca(2+) channel subunits and the reporter jellyfish green fluorescent protein for transient expression. Current from expressed channels (I(Ba)) and their response to MeHg applied acutely were measured using whole-cell voltage-clamp recording techniques and Ba(2+) (5 mM) as charge carrier. Amplitude of I(Ba) in these cells was reduced by the dihydropyridine (DHP), nimodipine, and enhanced by Bay K8644 [S-(-)-1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-[trifluoromethyl]phenyl)-3 pyridine carboxylic acid methyl ester]. MeHg (0.125-5.0 microM) caused a time- and concentration-dependent reduction in amplitude of the peak and sustained current through these channels. However, even at the highest concentration of MeHg tested, reduction of current amplitude by MeHg was incomplete. Washing with MeHg-free solution could not reverse its effects. The steady-state inactivation curve was unaltered by MeHg. Increasing the stimulation frequency or the extracellular Ba(2+) concentration each attenuated slightly the reduction in amplitude of I(Ba) by MeHg. In the presence of MeHg (5.0 microM), Bay K8644 still increased the remaining current, and nimodipine (10 microM) reduced residual current that was resistant to MeHg. Thus, although MeHg reduces the amplitude of recombinant, heterologously expressed L-type channel current, a portion of current is resistant to reduction by MeHg. Furthermore, DHP agonists and antagonists retain their ability to affect L-type Ca(2+) channel current even in the presence of MeHg.

Authors+Show Affiliations

Department of Pharmacology and Toxicology, Institute of Environmental Toxicology, Michigan State University, B331 Life Sciences Building, East Lansing, MI 48824-1317, USA.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

12130699

Citation

Peng, Shuangqing, et al. "Effects of Methylmercury On Human Neuronal L-type Calcium Channels Transiently Expressed in Human Embryonic Kidney Cells (HEK-293)." The Journal of Pharmacology and Experimental Therapeutics, vol. 302, no. 2, 2002, pp. 424-32.
Peng S, Hajela RK, Atchison WD. Effects of methylmercury on human neuronal L-type calcium channels transiently expressed in human embryonic kidney cells (HEK-293). J Pharmacol Exp Ther. 2002;302(2):424-32.
Peng, S., Hajela, R. K., & Atchison, W. D. (2002). Effects of methylmercury on human neuronal L-type calcium channels transiently expressed in human embryonic kidney cells (HEK-293). The Journal of Pharmacology and Experimental Therapeutics, 302(2), 424-32.
Peng S, Hajela RK, Atchison WD. Effects of Methylmercury On Human Neuronal L-type Calcium Channels Transiently Expressed in Human Embryonic Kidney Cells (HEK-293). J Pharmacol Exp Ther. 2002;302(2):424-32. PubMed PMID: 12130699.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effects of methylmercury on human neuronal L-type calcium channels transiently expressed in human embryonic kidney cells (HEK-293). AU - Peng,Shuangqing, AU - Hajela,Ravindra K, AU - Atchison,William D, PY - 2002/7/20/pubmed PY - 2002/8/30/medline PY - 2002/7/20/entrez SP - 424 EP - 32 JF - The Journal of pharmacology and experimental therapeutics JO - J Pharmacol Exp Ther VL - 302 IS - 2 N2 - Methylmercury (MeHg) disrupts the function of native, high voltage-activated neuronal Ca(2+) channels in several types of cells. However, the effects of MeHg on isolated Ca(2+) channel phenotypes have not been examined. The aim of the present study was to examine the action of MeHg on recombinant, neuronal L-type voltage-sensitive Ca(2+) channels. Human embryonic kidney cells (HEK-293) were transfected with human neuronal cDNA clones of the alpha(1C-1) subunit in combination with alpha(2b) and beta(3a) Ca(2+) channel subunits and the reporter jellyfish green fluorescent protein for transient expression. Current from expressed channels (I(Ba)) and their response to MeHg applied acutely were measured using whole-cell voltage-clamp recording techniques and Ba(2+) (5 mM) as charge carrier. Amplitude of I(Ba) in these cells was reduced by the dihydropyridine (DHP), nimodipine, and enhanced by Bay K8644 [S-(-)-1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-[trifluoromethyl]phenyl)-3 pyridine carboxylic acid methyl ester]. MeHg (0.125-5.0 microM) caused a time- and concentration-dependent reduction in amplitude of the peak and sustained current through these channels. However, even at the highest concentration of MeHg tested, reduction of current amplitude by MeHg was incomplete. Washing with MeHg-free solution could not reverse its effects. The steady-state inactivation curve was unaltered by MeHg. Increasing the stimulation frequency or the extracellular Ba(2+) concentration each attenuated slightly the reduction in amplitude of I(Ba) by MeHg. In the presence of MeHg (5.0 microM), Bay K8644 still increased the remaining current, and nimodipine (10 microM) reduced residual current that was resistant to MeHg. Thus, although MeHg reduces the amplitude of recombinant, heterologously expressed L-type channel current, a portion of current is resistant to reduction by MeHg. Furthermore, DHP agonists and antagonists retain their ability to affect L-type Ca(2+) channel current even in the presence of MeHg. SN - 0022-3565 UR - https://www.unboundmedicine.com/medline/citation/12130699/Effects_of_methylmercury_on_human_neuronal_L_type_calcium_channels_transiently_expressed_in_human_embryonic_kidney_cells__HEK_293__ L2 - https://jpet.aspetjournals.org/cgi/pmidlookup?view=long&pmid=12130699 DB - PRIME DP - Unbound Medicine ER -