title: Maintenance of bradykinin-induced intracellular calcium response of MDCK cells depends on extracellular calcium.
abstract: Bradykinin (BK) induces intracellular calcium ([Ca2+]i) release in Madin-Darby canine kidney (MDCK) cells. During long-term continuous BK exposure, cells become desensitized and fail to respond to a new BK stimulus. We used a protocol of repeated short-term BK addition and removal. MDCK cells were loaded with the Ca-indicator indo-1 and were exposed to BK (100 nmol/L) for 10 seconds, followed by BK removal. This cycle was repeated four to eight times while [Ca2+]i was continuously recorded. In a Ca-free bath, the cells gradually became completely desensitized to repeated BK stimuli. In the presence of 1 mmol/L or 10 mmol/L Cae, however, repeated addition of BK caused repeated [Ca2+]i transients with partial decrease of peak heights (327 and 436 nmol/L delta[Ca2+]i final) (partial desensitization). Repeated BK stimuli also led to partial desensitization (70% to 85%) to adenosine triphosphatase and carbachol (heterologous desensitization). BK also reduced peak thapsigargin response (70%), consistent with partial depletion of endoplasmic reticulum Ca pools. Our results show that MDCK cells maintain their sensitivity to BK during repeated short-term BK exposures. Available Ca3 plays a major role in modulating the degree of cellular responsiveness.
authors.affiliation: Renal Section, Veterans Affairs Medical Center, Kansas City, MO 64128, USA.
authors.forename: S
authors.initials: S
authors.lastname: Vamos
authors.forename: L W
authors.initials: LW
authors.lastname: Welling
authors.forename: T B
authors.initials: TB
authors.lastname: Wiegmann
mesh_terms: D000818:Animals; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004285:Dogs; D007668:Kidney / Q000187:drug effects / Q000378:metabolism; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin
chemical_list: D013729:Terpenes; D019284:Thapsigargin; D001920:Bradykinin; D002118:Calcium