Activation of phospholipase C by different effectors in rat placental cells.

The present communication documents the accumulation of inositol phosphates in rat placental cells by fluoride as well as by vanadate. These findings suggest the existence of the phosphoinositide pathway and its modulation by a G-protein. A concomitant action of fluoride on phosphoinositide breakdown was also observed.

Comparison of inositol phosphates accumulation induced by different effectors in rat thyroid slices.

Rat thyroid slices were submitted to different effectors and hormones in order to investigate their action on the phosphatidylinositol metabolism. Fluoride and vanadate induced a clear increase of the inositol phosphates with half maximal stimulation at 7 mM and 8 mM respectively. The inositol bisphosphate (IP2) and inositol trisphosphate (IP3) accumulation induced by vanadate was relatively higher than that observed in the case of fluoride stimulation.

[Isolation of protein kinase C isoforms from human full-term placenta].

Protein kinase C isolated from human term placenta was resolved by hydroxyapatite column chromatography into two major fractions corresponding to type II (beta sequence) and type III (alpha sequence) PKC isolated from rat brain. Both subspecies were stimulated by Ca2+ with a different sensitivity. No effect of arachidonic acid on their activity was observed.

Isolation and characterization of protein kinase C from human placenta.

Protein kinase C (Ca2+ and phospholipid-dependent protein kinase) was detected in human placenta and was partially purified using DEAE cellulose chromatography and Ultrogel filtration. Diolein alone did not act on this enzyme but exerted a strong stimulatory action when associated with phosphatidylserine and Ca2+. Similar results were obtained with the phorbol myristate acetate.