Maintenance of bradykinin-induced intracellular calcium response of MDCK cells depends on extracellular calcium
Vamos, S.; Welling, L.W.; Wiegmann, T.B.
Journal of Laboratory and Clinical Medicine 125(4): 470-478
1995
ISSN/ISBN: 0022-2143 PMID: 7706902 Document Number: 440507
Bradykinin (BK) induces intracellular calcium ((Ca-2+)-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 expressed to BK (100 nmol/L) for 10 seconds, followed by BK removal. This cycle was repeated four to eight times while (Ca-2+)-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 Ca-e, however, repeated addition of BK caused repeated (Ca-2+)-i transients with partial decrease of peak heights (327 and 436 nmol/L DELTA(Ca-2+)-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 Ca-3 plays a major role in modulating the degree of cellular responsiveness.