Influence of probes for calcium-calmodulin and protein kinase C signalling on the plasma membrane Ca2+-ATPase activity of rat synaptosomes and leukocyte membranes.
The influence of selected inhibitors of calcium signalling on the plasma membrane Ca2+-ATPase activity of rat synaptosomes and peritoneal leukocyte membranes was studied. The calmodulin inhibitor calmidazolium was an efficient inhibitor (50%) of the synaptosomal Ca2+-ATPase activity in a manner competitive with phosphatidylserine. The inhibition by CGS 9343B (30%) was not counteracted by phosphatidylserine. The intracellular calcium antagonist TMB-8 and the protein kinase inhibitor staurosporine and the derivatives CGP 41251 and CGP 42700 hardly affected the synaptosomal Ca2+-ATPase activity. The flavonoid quercetin was a more effective inhibitor of the ATPase activity of synaptosomal than of leukocyte membranes. Phloretin, at relatively high concentrations, caused only a modest inhibition of synaptosomes. The protein kinase C inhibitor sphingosine was a weak inhibitor of the synaptosomal but an effective inhibitor of the leukocyte membrane Ca2+-ATPase activity. The antineoplastic ether phospholipids BM 41.440 (ilmofosine) and ET-18-OCH3 (edelfosine) effectively inhibited the leukocyte membranes whereas the ATPase activity of synaptosomes was significantly increased by 20 microM and slightly inhibited by higher concentrations of these agents. The analogue hexadecylphosphocholine (miltefosine) did not affect the ATPase activity of the synaptosomes and only inhibited that of the leukocyte membranes at concentrations above 20 microM. These results show that several test substances of current interest affect the activity of the plasma membrane Ca2+-ATPase. The effects depend on the origin of the membranes. The investigation does not permit a distinction between direct effects on the enzyme and an interference with its membrane environment although the latter is indicated for the ether phospholipids.
Grosman
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Department of Pharmacology, The Panum Institute, University of Copenhagen, Denmark.
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000187:drug effects* / Q000378:metabolism; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007962:Leukocytes / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010742:Phospholipid Ethers / Q000494:pharmacology; D010767:Phosphorylcholine / Q000031:analogs & derivatives / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D011794:Quercetin / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013110:Sphingosine / Q000494:pharmacology; D019311:Staurosporine / Q000031:analogs & derivatives / Q000494:pharmacology; D013574:Synaptosomes / Q000187:drug effects / Q000201:enzymology*
D002121:Calcium Channel Blockers; D002147:Calmodulin; D004791:Enzyme Inhibitors; D007093:Imidazoles; D010726:Phosphodiesterase Inhibitors; D010742:Phospholipid Ethers; D010767:Phosphorylcholine; C073761:CGP 42700; C026659:edelfosine; C031938:calmidazolium; C039128:miltefosine; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; C043297:ilmofosine; D005707:Gallic Acid; D011794:Quercetin; D011493:Protein Kinase C; D000252:Calcium-Transporting ATPases; D019311:Staurosporine; C059539:midostaurin; D013110:Sphingosine; D002118:Calcium