| 17294162 |
Clark JM, Symington SB: Pyrethroid action on calcium channels: neurotoxicological implications. Invert Neurosci. 2007 Mar;7(1):3-16. Epub 2007 Feb 9.
Actions of cismethrin versus deltamethrin were compared using two functional attributes of rat brain synaptosomes. Both pyrethroids increased calcium influx but only deltamethrin increased Ca (2+)-dependent neurotransmitter release following K (+)-stimulated depolarization. The action of deltamethrin was stereospecific, concentration-dependent, and blocked by omega-conotoxin GVIA. These findings delineate a separate action for deltamethrin and implicate N-type rat brain Ca (v) 2.2 voltage-sensitive calcium channels (VSCC) as target sites that are consistent with the in vivo release of neurotransmitter caused by deltamethrin. Deltamethrin (10 (-7) M) reduced the peak current (approx. -47%) of heterologously expressed wild type Ca (v) 2.2 in a stereospecific manner. Mutation of threonine 422 to glutamic acid (T422E) in the alpha (1)-subunit results in a channel that functions as if it were permanently phosphorylated. Deltamethrin now increased peak current (approx. +49%) of T422E Ca (v) 2.2 in a stereospecific manner. Collectively, these results substantiate that Ca (v) 2.2 is directly modified by deltamethrin but the resulting perturbation is dependent upon the phosphorylation state of Ca (v) 2.2. Our findings may provide a partial explanation for the different toxic syndromes produced by these structurally-distinct pyrethroids. |
199(2,3,4,4) |