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ATP a potent regulator of inositol phospholipids-phospholipase C and lipid mediators in brain cortex

100%

Strosznajder J. , Strosznajder R. P.

Acta Neurobiologiae Experimentalis

1996

tom 56

nr 2

527-534

Adenosine-5'triphosphate (ATP) is stored and co-released with various neurotransmitters but it may also act as a fast excitatory neurotransmitter trough the activation of purinoreceptor(s).In this study the effcet of ATP on phospholipase C (PLC) degrading labelled PtdIns(4,5)P2 and PtdIns in brain cortex slices, brain homogente and subcellular fractions was investigated.It was found the ATP added into brain slices activated significantly and specifically PtdIns(4,5)P2 degradation and this process was inhibited by theophylline.Moreover, ATP maintained a higher level of inositol(1,4,5,)P3 radioactivity in total water-soluble inositol metabolites.However, ATP added directly for the assay of PLC into brain homogenate of subcellular fractions inhibits phosphoinositide degradation in a eceptor-independend manner and suppresses conversion of Ins(1,4,5)P3 into Ins(1,4)P2.Our results indicate that ATP acting extracellularly through a purinergic receptor(s) activates PtdIns(4,5)P2 degradation and release of Ins(1,4,5)P3.ATP acting directly on PLC inhibits in a receptor-independent manner phosphoinositide degradation, and protect against liberation of lipid-derived second messengers.

Light activation of phospholipase A2 in the photoreceptor of the crayfish (Procambarus clarkii)

88%

Kashiwagi T. , Meyer-Rochow V. B. , Nishimura K. , Eguchi E.

Acta Neurobiologiae Experimentalis

2000

tom 60

nr 1

9-16

Retinal lipids of crayfish, kept at 4oC under continuous darkness for 3 weeks, consisted mainly of phosphatidylcholine (PC) and phosphatidylethanolamine (PE); sphingomyelin (SM), phosphatidylinositol (PI) and phosphatidylserine (PS) were minor contributors. PI, involved in the phototransduction cascade, never reached greater concentrations than 7% of the total. High concentrations of polyunsaturated fatty acids (PUFA) such as 20:4n-6, 20:5n-3 and 22:6n-3 (DHA, docosahexaenoic acid) were present in PC, PE and PS, but scarce in SM and PI. In retinae of crayfish kept at 4oC in darkness for 3 weeks and then exposed to white light (6 h; ca. 4,500 lx), SM and PS remained seemingly unaffected. PC, however, significantly decreased within 10 min to 65% of the initial value and 50% at 180 min. To study the reduction of PC, lipids of retinae suspended in physiological solution with/without phospholipase C (PLC) and phospholipase A2 (PLA2) inhibitors such as DMDA (=DEDA), manoalide, ET-18-OCH3, and U-73122 were measured. Only free fatty acids (FFA) of retinae with inhibitors of PLA2 like DMDA and manoalide decreased. Retinae irradiated by white light for 3 h displayed a significant reduction of PC, compared with those that had remained in continuous darkness. However, the PC of retinae with PLA2-inhibitors was not decreased by light. Our results provide evidence that not only photoreceptor cell PLC, but also PLA2 is activated by light.