English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The regulation of phosphatidylcholine (PtdCho) hydrolysis by Ca2+ and protein kinase C (PKC) was measured in [3H]palmitate-labelled cultured guinea-pig airway smooth-muscle cells as phosphatidylbutanol ([3H]PtdBut) and phosphatidate ([3H]PtdOH) formation in the presence of butanol. The former is a direct measure of phospholipase D (PLD) activity, whereas the latter, in airway smooth muscle, is indicative of net PtdCho-specific phospholipase C (PLC)-like/diacylglycerol (DG) kinase activity. Bradykinin-stimulated responses exhibited a requirement for extracellular Ca2+ influx, since they were inhibited in the presence of EGTA. This influx was independent of voltage-operated channels, since the L-type channel blocker nifedipine (up to 10 microM) was without effect on bradykinin-stimulated responses. In support of this, membrane depolarization with KCl (30 mM) failed to elicit either response. However, bradykinin-stimulated formation of both [3H]PtdBut and [3H]PtdOH was partially inhibited by 100 microM SKF96365. Ionomycin, a Ca2+ ionophore, induced PtdCho hydrolysis to a greater extent than bradykinin, also in an extracellular-Ca(2+)-dependent manner. Thapsigargin-induced emptying of intracellular Ca2+ pools elicited the formation of both [3H]PtdBut and [3H]PtdOH and displayed a requirement for extracellular Ca2+. Bradykinin-stimulated PtdCho-specific PLC-like/DG kinase pathway and PLD responses were unaffected by thapsigargin pretreatment, thereby questioning the role of Ins(1,4,5)P3/Ins(1,3,4,5)P4-dependent Ca2+ stores in the receptor stimulation of these activities in airway smooth-muscle cells. In this regard, we have previously demonstrated that the bradykinin-stimulated PtdCho-specific PLD and PLC-like activities can occur under conditions of apparent complete blockade of bradykinin-stimulated Ins(1,4,5)P3 formation by receptor antagonist in guinea-pig airway smooth muscle. The PKC inhibitor, Ro31-8220, selectively blocked both bradykinin- and ionomycin-stimulated PLD activity in a concentration-dependent manner (IC50 approx. 1 microM), but was without effect on bradykinin-stimulated PtdCho-PLC-like/DG kinase-derived PtdOH formation. In contrast, an inhibitor of PtdCho-PLC, D609, selectively blocked the formation of [3H]PtdOH in the presence of butanol (PtdCho-PLC-like/DG kinase activity), but not [3H]PtdBut formation. In conclusion, PtdCho hydrolysis appears to occur via two distinguishable routes which both require extracellular Ca2+, whereas only the PLD route is regulated by PKC.

Bradykinin-stimulated phosphatidylcholine hydrolysis in airway smooth muscle: the role of Ca2+ and protein kinase C