title: The effect of lead on cells cultivated in vitro. II. Chronic exposure and development of resistance.
abstract: In a previous communication the acute effects of anorganic lead salts on L-A mouse fibroblasts cells cultured in vitro have been described. This report presents the results of long-term tests with L-A cells. Under continuous exposure lead tolerance developed, even to concentrations exceeding the LD50. The kinetics of the acquirement of resistance are demonstrated. The resistant cells adjusted more quickly to higher doses of the heavy metal than the controls. Low-resistance strains retained the growth characteristics of the parent cells, but with increasing levels of lead tolerance multiplication rates decreased significantly. After approximately 60 generations in lead-free environment the cells had to a major degree lost their resistance indicating that the induced lead tolerance is caused by adaptation rather than by mutation and selection. Lead resistance appears not to depend on lead exclusion, for the lead content of resistant cells and lead-exposed controls was found to be of a comparable order of magnitude.
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D002452:Cell Count; D002455:Cell Division / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D007739:L Cells / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D007854:Lead / Q000378:metabolism / Q000494:pharmacology*; D007928:Lethal Dose 50; D051379:Mice; D013997:Time Factors
chemical_list: D007854:Lead