title: Lead induction of crop dysfunction in pigeons through a direct action on neural or smooth muscle components of crop tissue.
abstract: Lead acetate solutions administered p.o. to pigeons produce crop stasis. Crop dysfunction may be an indirect effect on crop activity by a direct interaction with the cerebellum or some other site associated with lead-induced ataxia. Alternatively, crop stasis may be due to the direct interaction of lead with sites on the smooth muscle or neural elements in crop tissue. A behavioral test for ataxia was performed on pigeons given lead by crop intubation or i.m. injection. Blood lead concentrations were also monitored. Lead-induced ataxia was separable from lead-induced crop dysfunction depending on the route of lead administration, suggesting that lead-induced crop stasis is not secondary to toxicity at a site associated with ataxia. Intramuscular treatment produced crop stasis more readily than did crop intubation. This probably reflects different mechanisms of absorption and metabolism. A Tris-succinate medium was devised which accommodated the solubility characteristics of lead, permitting studies of crop tissue in vitro. Lead chloride added to crop tissue in tris-succinate medium caused a concentration-related reversible relaxation. Crop circular muscle was more sensitive to Pb++ than was longitudinal muscle, in agreement with the effects of other agonists. The EC30 of crop circular smooth muscle in plasma was 1000 microM PbCl2 compared to 3 microM in Tris-succinate medium. The results suggest that lead induces crop dysfunction by acting either directly on crop smooth muscle or on neural elements in crop tissue.
authors.forename: I J
authors.initials: IJ
authors.lastname: Boyer
authors.forename: D A
authors.initials: DA
authors.lastname: Cory-Slechta
authors.forename: V
authors.initials: V
authors.lastname: DiStefano
mesh_terms: D000818:Animals; D001259:Ataxia / Q000139:chemically induced; D002531:Cerebellum / Q000187:drug effects; D010856:Columbidae; D003426:Crop, Avian / Q000187:drug effects* / Q000294:innervation; D003470:Culture Media; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D066298:In Vitro Techniques; D002479:Inclusion Bodies / Q000187:drug effects; D007854:Lead / Q000097:blood / Q000633:toxicity*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*
chemical_list: D003470:Culture Media; D007854:Lead