Rapid breakdown of phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate in rat hepatocytes stimulated by vasopressin and other Ca2+-mobilizing hormones

Pharmacological studies suggest that each of the four stimuli acts at a different population of receptors

J A Creba; C P Downes; P T Hawkins; G Brewster; R H Michell; C J Kirk

2015

Key concepts

Scholarcy highlights

  • Pharmacological studies suggest that each of the four stimuli acts at a different population of receptors
  • Disappearance of labelled PtdIns4P and PtdIns(4,5)P2 is not observed when cells are incubated with the ionophore A23187
  • The hormone-stimulated polyphosphoinositide disappearance is reduced, but not abolished, in Ca2+-depleted cells. These hormonal effects are not modified by 8-bromo cyclic GMP, cycloheximide or delta-hexachlorocyclohexane
  • The absolute rate of polyphosphoinositide breakdown in stimulated cells is similar to the rate previously reported for the disappearance of phosphatidylinositol [Kirk, Michell & Hems Biochem
  • It seems likely that these changes in polyphosphoinositide labelling are caused by hormonal activation of the breakdown of PtdIns(4,5)P2 by the action of a polyphosphoinositide phosphodiesterase
  • We suggest that the initial response to hormones is breakdown of PtdIns(4,5)P2, and that the simultaneous disappearance of phosphatidylinositol might be a result of its consumption for the continuing synthesis of polyphosphoinositides

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