Boyer I J, DiStefano V
J Pharmacol Exp Ther. 1985 Sep;234(3):616-23.
Lead-induced crop dysfunction is probably due to a direct action on the smooth muscle or the neural elements in crop tissue. Strips of crop tissue relax when exposed to lead chloride in vitro. We found that tetrodotoxin and the neurotransmitter antagonists propranolol, sotalol and apamin failed to alter lead-induced relaxation, suggesting that the effect is not neurally mediated. Lead, manganese, cadmium and theophylline inhibited calcium-induced contractions in depolarized crop tissue. However, lead, like the phosphodiesterase inhibitor theophylline and unlike the calcium-influx blocker verapamil, did not inhibit bethanechol- or potassium-stimulated contractions and calcium influx into crop tissue. This suggests that lead does not act by blockade of calcium influx. Lead stimulated cyclic AMP production in cell-free crop membrane preparations. Lead also enhanced manganese stimulation of cyclic AMP production. The results suggest that lead-induced relaxation may be due to stimulation of adenylate cyclase activity resulting in increased intracellular cyclic AMP levels.
铅导致的嗉囊功能障碍可能是由于其对嗉囊组织中的平滑肌或神经成分的直接作用。在体外，当嗉囊组织条暴露于氯化铅时会松弛。我们发现，河豚毒素以及神经递质拮抗剂普萘洛尔、索他洛尔和蜂毒肽均未能改变铅诱导的松弛，这表明该效应并非由神经介导。铅、锰、镉和茶碱抑制去极化嗉囊组织中钙诱导的收缩。然而，与磷酸二酯酶抑制剂茶碱一样但与钙内流阻滞剂维拉帕米不同，铅并不抑制氨甲酰甲胆碱或钾刺激的收缩以及钙流入嗉囊组织。这表明铅并非通过阻断钙内流起作用。铅在无细胞的嗉囊膜制剂中刺激环磷酸腺苷（cAMP）的产生。铅还增强了锰对环磷酸腺苷产生的刺激作用。结果表明，铅诱导的松弛可能是由于腺苷酸环化酶活性受到刺激，导致细胞内环磷酸腺苷水平升高。
