Cholesterol depletion alters coronary artery myocyte Ca(2+) signalling in a stimulus-specific manner.
Bottom Line: We found that cholesterol depletion caused a selective modification of ion channel function, with whole cell inward Ca(2+) current being unaltered, whereas outward K(+) current was increased, due to BK(Ca) channel activation.There was also a significant decrease in cell capacitance.These data are discussed in terms of the involvement of caveolae in receptor localisation, Ca(2+) entry pathways and SR Ca(2+) release, and the role of these in agonist signalling.
Affiliation: University of Liverpool, Merseyside, UK. firstname.lastname@example.orgShow MeSH
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Mentions: MCD has been reported to elevate basal intracellular Ca2+. Therefore, in order to determine whether this elevation of outward current in the presence of MCD is due to activation of Ca2+-dependent K+ currents, we examined the effects of 3 selective channel blockers: iberiotoxin (100 nM) to block large conductance (BKCa) channels, TRAM-34 (100 nM) to block intermediate conductance (IKCa) channels and apamin (100 nM) to block small conductance (SKCa) channels. The main protocol used to assess the inhibitory nature of these antagonists involved pre-treatment with the blocker and then a challenge with MCD. We also confirmed the result by using MCD first to increase outward current and then applying the blocker on top. Iberiotoxin pre-treatment significantly inhibited the increase in outward current observed with MCD (2.42 ± 0.28-fold, n = 11 versus 1.37 ± 0.16-fold, n = 5, P = 0.029). When cholesterol was depleted with MCD first, iberiotoxin entirely ablated the MCD-induced increase in outward current (Fig. 7A, n = 3). TRAM-34 failed to alter the increase in K+ current observed with MCD using either protocol (Fig. 7B, 2.42 ± 0.28-fold versus 1.97 ± 0.21-fold, n = 5, P = 0.32). Similarly, apamin failed to alter the increase in K+ current observed with MCD (Fig. 7B, 2.42 ± 0.28-fold versus 2.1 ± 0.23-fold, n = 5, P = 0.43). It was confirmed that the DMSO and apamin vehicle controls had no effect on outward current.
Affiliation: University of Liverpool, Merseyside, UK. email@example.com