{"doi":"10.1177/108155899604400611","title":"Characterization of Intracellular Calcium Pools and Their Desensitization in Thermotolerant Human A-431 Cells","abstract":"\n Background\n \n This study characterizes the intracellular Ca\n 2+\n pools in nonthermotolerant and thermotolerant human A-431 cells and the reduced cytotoxicity using the inhibitors of Ca\n 2+\n mobilizations.\n \n \n \n Methods\n \n Nonthermotolerant and thermotolerant cells were treated with different Ca\n 2+\n mobilizers in the absence of external Ca\n 2+\n . The cytosolic Ca\n 2+\n concentration using fura-2 fluorescence probe was measured to identify the presence of intracellular Ca\n 2+\n pools. The cytotoxicity of the increase in [Ca\n 2+\n ]\n i\n was studied using the colony forming efficiency assay.\n \n \n \n Results\n \n The resting intracellular Ca\n 2+\n concentration ([Ca\n 2+\n ]\n i\n ) in the absence of extracellular Ca\n 2+\n was 42 ± 9 nm, determined by fura-2. Bradykinin (10 μmol/L), monensin (200 μmol/L), and ionomycin (1 μmol/L) sequentially treated to cells mobilized Ca\n 2+\n and increased [Ca\n 2+\n ]\n i\n by 64 ± 23, 40 ± 6, and 59 ± 21 nm, respectively. The bradykinin effect was blocked by 5 μmol/L U-73122 (an inhibitor of inositol trisphosphate production); the ionomycin effect was inhibited by increasing intracellular pH (pH\n i\n ) or treatment with 100 μmol/L ryanodine while the monensin effect was enhanced by increasing pH\n i\n , but was not inhibited by ryanodine. Cells that were made tolerant to lethal temperatures also responded to bradykinin, monensin, and ionomycin, but the magnitude of the response was diminished. Subsequent treatments with bradykinin, monensin, and ionomycin increased [Ca\n 2+\n ]; in thermotolerant cells to levels 68 ± 8, 44 ± 5, and 45±5%, respectively, of values found in nonthermotolerant cells. Higher concentrations of these agents did not further increase [Ca\n 2+\n ]\n i\n . The bradykinin-induced increase in inositol trisphosphates in thermotolerant cells was also reduced, which perhaps accounts for the attenuation in Ca\n 2+\n mobilization. Unlike nonthermotolerant cells, the monensin effect was not enhanced when pH\n i\n was increased. However, the ionomycin effect was still dependent on pH\n i\n and was blocked by ryanodine at a higher concentration.\n \n \n \n Conclusions\n \n These results show that there are bradykinin-, monensin-, and ryanodine-sensitive pools and that thermotolerance attenuates Ca\n 2+\n mobilization stimulated by these three agents. Ionomycin at 10 μmol/L or NaCN at 10 mM for 1 hour demonstrated cytotoxicity. Pretreatment with 100 μmol/L ryanodine and/or 5 μmol/L U-73122 reduced cytotoxicity produced by either NaCN or ionomycin. These results suggest that an attenuation of [Ca\n 2+\n ]\n i\n increases can diminish cytotoxicity\n \n ","journal":"Journal of Investigative Medicine","year":1996,"id":28920,"datarank":0.3453877639491069,"base_score":2.302585092994046,"endowment":2.302585092994046,"self_citation_contribution":0.3453877639491069,"citation_network_contribution":0.0,"self_endowment_contribution":0.3453877639491069,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":9,"citer_count":1,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":null,"is_data_producer":false,"deposit_databanks":null,"is_oa":false,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":null,"fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":160725,"name":"Michael L. Koenig","orcid":null,"position":1,"is_corresponding":false},{"id":160724,"name":"Juliann Gong Kiang","orcid":null,"position":0,"is_corresponding":false}],"reference_count":0,"raw_metadata":{"has_enrichment":true,"base_score":2.302585092994046,"endowment":2.302585092994046,"datacite_reuse_total":0,"file_count":0,"downloads":0,"views":0,"has_version_chain":false,"is_dataset":false,"is_oa":false,"pmid":"8795298","pmcid":null,"openalex_id":"https://openalex.org/W2416299159","authors":[],"funders":[],"total_grants":0,"fwci":1.3103,"citation_percentile":0.7824448,"influential_citations":0,"citation_trend":[],"oa_status":"closed","license":"https://journals.sagepub.com/page/policies/text-and-data-mining-license","oa_locations":[{"url":"https://journals.sagepub.com/doi/pdf/10.1177/108155899604400611","host_type":"publisher"},{"url":"https://journals.sagepub.com/doi/full-xml/10.1177/108155899604400611","host_type":"publisher"},{"url":"https://doi.org/10.1177/108155899604400611","host_type":"journal"},{"url":"https://pubmed.ncbi.nlm.nih.gov/8795298","host_type":"repository"}],"fields_of_study":["Ion Channels and Receptors","Protein Kinase Regulation and GTPase Signaling","Calpain Protease Function and Regulation","Chemistry","Medicine","Biology"],"mesh_terms":["Adaptation, Physiological","Calcium","Cytosol","Hot Temperature","Humans","Tumor Cells, Cultured"],"keywords":["Ionomycin","Intracellular","Monensin","Bradykinin","Extracellular","Fura-2","Ryanodine receptor","Inositol","Calcium","Calcium in biology","Internal medicine","Endocrinology","Chemistry","Biology","Cytosol","Biochemistry","Biophysics","Medicine","Enzyme","Receptor"],"sdg_mappings":[],"linked_datasets":[],"clinical_trials":[],"software_tools":[],"database_accessions":[],"source":"live","citation_network_status":"fetched"},"created_at":"2026-06-08T22:21:51.894891Z","pmid":null,"pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}