Lindane-Induced Elimination of Gap Junctional Communication in Rat Uterine Myocytes Is Mediated by an Arachidonic Acid-Sensitive cAMP-Independent Mechanism

Abstract

Previous studies by this laboratory showed that the pesticide lindane rapidly and potently inhibits gap junctional communication in myometrial smooth muscle cells. This study examined the possible role of cAMP or arachidonic acid in lindane′s elimination of myometrial gap junctional communication. Lindane produced concentration-dependent increases in cAMP of 1.21, 2.94, 6.06, and 8.69 pmol/mg protein with 0.1, 1, 30, and 100 μM lindane, respectively, compared to solvent-treated controls (1.27 pmol/mg protein). Lindane also increased release of tritiated arachidonic acid to 342, 509, 852, 1236, 1639, and 4454 dpm/μg protein with 0.01, 0.1, 1, 10, and 100 μM lindane, respectively, compared to solvent controls (342 dpm/mu g protein). Transfer of Lucifer Yellow dye was used as a measure of gap junctional communication. Both 8-br-cAMP (98, 97, 54, and 4% transfer seen with 0, 1, 10, and 100 μM cAMP) and arachidonic acid (98, 73, 54, 31, and 0% dye transfer for 0.1, 1, 10, 100, and 1000 nM arachidonic acid) depressed dye transfer in cultured myocytes. Although the adenylate cyclase inhibitor 2′,3′-dideoxyadenosine completely reversed forskolin-induced depression of dye transfer (1 μM forskolin, 22% transfer), it had no effect with lindane, indicating that lindane′s depression of dye transfer was independent of adenylate cyclase activation. Lindane′s inhibition of dye transfer was effectively reversed by growing myometrial cells under arachidonic acid-free conditions in the presence of eicosapentaenoic acid, a fatty acid that competes with arachidonic acid for the sn-1,2 position of membrane phospholipids: 0, 15, 40, and 88% dye transfer occurred in the presence of 0.01, 0.1, 1, and 10 μM eicosapentaenoic acid with 30 μM lindane. This implies that arachidonic acid release may be a critical event associated with lindane′s inhibition of gap junctional communication in uterine myocytes.