This study was conducted to investigate the effects of extremely low frequency electromagnetic fields (EMF) on signal pathway in plasma membrane of cultured cells (RAW 264.7 cells and RBL 2H3 cells), by measuring the activity of phospholipase A2 (PLA2), phospholipase C (PLC) and phospholipase D (PLD). The cells were exposed to the EMF (60 Hz, 0.1 or 1 mT) for 4 or 16 h. The basal and 0.5 microM melittin-induced arachidonic acid release was not affected by EMF in both cells. In cell-free PLA2 assay, we failed to observe the change of cPLA2 and sPLA2 activity. Also both PLC and PLD activities did not show any change in the two cell lines exposed to EMF. This study suggests that the exposure condition of EMF (60 Hz, 0.1 or 1 mT) which is 2.4 fold higher than the limit of occupational exposure does not induce phospholipases-associated signal pathway in RAW 264.7 cells and RBL 2H3 cells.
Arachidonic Acid ; Cell Line ; Cell Membrane ; Cells, Cultured ; Electromagnetic Fields ; Magnets ; Occupational Exposure ; Phospholipase D ; Phospholipases ; Phospholipases A2 ; Pyridoxal ; Signal Transduction ; Type C Phospholipases

No abstract available.
Phosphatidylcholines* ; Phospholipases A2* ; Phospholipases*

Animals ; Cardiovascular System ; chemistry ; Female ; Group II Phospholipases A2 ; blood ; Group IV Phospholipases A2 ; blood ; Group V Phospholipases A2 ; blood ; Group X Phospholipases A2 ; blood ; Male ; RNA, Messenger ; genetics ; Rats ; Rats, Wistar

No abstract available.
Animals ; Inositol* ; Kidney* ; Liver* ; Phospholipases* ; Rats* ; Type C Phospholipases*

Contraction of smooth muscle is initiated by an increase in cytosolic Ca2+ leading to activation of Ca2+/calmodulin-dependnet myosin light chain (MLC) kinase and phosphorylation of MLC. The types of contraction and signaling mechanisms mediating contraction differ depending on the region. The involvement of these different mechanisms varies depending on the source of Ca2+ and the kinetic of Ca2+ mobilization. Ca2+ mobilizing agonists stimulate different phospholipases (PLC-beta, PLD and PLA2) to generate one or more Ca2+ mobilizing messengers (IP3 and AA), and diacylglycerol (DAG), an activator of protein kinase C (PKC). The relative contributions of PLC-beta, PLA2 and PLD to generate second messengers vary greatly between cells and types of contraction. In smooth muscle cell derived form the circular muscle layer of the intestine, preferential hydrolysis of PIP2 and generation of IP3 and IP3-dependent Ca2+ release initiate the contraction. In smooth muscle cells derived from longitudinal muscle layer of the intestine, preferential hydrolysis of PC by PLA2, generation of AA and AA-mediated Ca2+ influx, cADP ribose formation and Ca2+/-induced Ca2+ release initiate the contraction. Sustained contraction, however, in both cell types is mediated by Ca2+/-independent mechanism involving activation of PKC- epsilon by DAG derived form PLD. A functional linkage between G13, RhoA, ROCK, PKC- epsilon, CPI-17 and MLC phosphorylation in sustained contraction has been implicated. Contraction of normal esophageal circular muscle (ESO) in response to acetylcholine (ACh) is linked to M2 muscarinic receptors activating at least three intracellular phospholipases, i.e. phosphatidylcholine-specific phospholipase C (PC-PLC), phospholipase D (PLD) and the high molecular weight (85 kDa) cytosolic phospholipase A2 (cPLA2) to induce phosphatidylcholine (PC) metabolism, production of diacylglycerol (DAG) and arachidonic acid (AA), resulting in activation of a protein kinase C (PKC)-dependent pathway. In contrast, lower esophageal sphincter (LES) contraction induced by maximally effective doses of ACh is mediated by muscarinic M3 receptors, linked to pertussis toxin-insensitive GTP-binding proteins of the Gq/11 type. They activate phospholipase C, which hydrolyzes phosphatidylinositol bisphosphate (PIP2), producing inositol 1, 4, 5-trisphosphate (IP3) and DAG. IP3 causes release of intracellular Ca2+ and formation of a Ca2+/-calmodulin complex, resulting in activation of myosin light chain kinase and contraction through a calmodulin-dependent pathway.
Acetylcholine ; Arachidonic Acid ; Cyclic ADP-Ribose ; Cytosol ; Esophageal Sphincter, Lower ; GTP-Binding Proteins ; Hydrolysis ; Inositol ; Intestines ; Metabolism ; Molecular Weight ; Muscle, Smooth* ; Myocytes, Smooth Muscle ; Myosin Light Chains ; Myosin-Light-Chain Kinase ; Negotiating ; Phosphatidylcholines ; Phosphatidylinositols ; Phospholipase D ; Phospholipases ; Phospholipases A2 ; Phosphorylation ; Phosphotransferases ; Protein Kinase C ; Receptor, Muscarinic M3 ; Receptors, Muscarinic ; Second Messenger Systems ; Type C Phospholipases ; Whooping Cough

BACKGROUND: Diabetic patients develop hypoaldosteronism which frequently caused hyperkalemia and metabolic acidosis and diabetic hypoaldosteronism is associated with selective unresponsiveness of aldosterone to angiotensin A-II, but mechanism of defect in A-II stimulated aldosterone response still remain unclear. METHODS: To elucidate the mechanism of defect in A-II stimulated aldosterone response, author evaluated the responses of aldosterone production to A-II, K+, and ACTH in adrenal glomerulosa cells prepared from streptozotocin induced diabetic rats, Inositol triphosphate (IP3) generated by activation of phospholipase C (PLC) and arachidonic acid and lysophospholipids generated by activation of phospholipase A2 (PLA2) were measured in A-II stimulated glomerulosa cells. Radiocalcium efflux and aldosterone response to second messenger of A-II such as PLC, IP3, PLA, AA and protein kinase C activator, 12-o-tetradecanoylphorbol 13 acetate (TPA). RESULTS: 1. Plasma renin activity and aldosterone levels were not different among control rats, untreated and insulin treated diabetic rats. 2. Basal, ACTH and K+ -stimulated aldosterone production were similar in cells from the three groups (p<0.05), but A-II stimulated aldosterone production was significantly decreased in cells from untreated diabetic rats compared with control and insulin treated diabetic rats (p<C0.05). 3. A-II induced IP3, AA and lysophospholipids generation and 45Ca efflux were similar among the three groups (p>0.05). 4. Aldosterone responses to PLC, IP3, AA and TPA were significantly decreased in glomerulosa cells from diabetic rats compared with control and insulin treated diabetic rats (p<0.05), but aldosterone response to PLA2 was similar among the three groups (p>0.05). 45Ca efflux to PLC, IP3 PLA2 and AA were similar among the three groups (p>0.05). CONCLUSION: These results suggested that decreased A-II-stimulated aldosterone response was present in glomerulosa cells from streptozotocin induced diabetic rats and reversed by insulin treatments. The main defect of altered A-II response of zona glomerulosa might be located in the step after activation of phospholipase and increase of intracellular calcium, and activation of PKC, or distal to that could be one of the causative mechanism.
Acidosis ; Adrenocorticotropic Hormone ; Aldosterone* ; Angiotensin II ; Angiotensins* ; Animals ; Arachidonic Acid ; Calcium* ; Diabetes Mellitus ; Humans ; Hyperkalemia ; Hypoaldosteronism ; Inositol ; Insulin ; Lysophospholipids ; Phospholipases A2 ; Phospholipases* ; Plasma ; Protein Kinase C ; Rats* ; Renin ; Second Messenger Systems ; Streptozocin ; Type C Phospholipases ; Zona Glomerulosa*

Cromakalim (BRL 34915), known as an airway smooth muscle relaxant, inhibited the releases of mediators in the antigen-induced mast cell activation. It has been suggested that cromakalim, in part, inhibited mediator releases by inhibiting the initial increase of 1,2-diacylglycerol (DAG) produced by the activation of the other phospholipase system which is different from phosphatidylcholine-phospholipase D pathway. The aim of this study is to further examine the inhibitory mechanism of cromakalim on the mediator release in the mast cell activation. Guinea pig lung mast cells were purified by using enzyme digestion and percoll density gradient. In purified mast cells prelabeled with (3H)PIP2, phospholipase C (PLC) activity was assessed by the production of (3H)insitol phosphates. Protein kinase C (PKC) activity was assessed by measuring the protein phosphorylated from mast cells prelabeled with (gamma-32P)ATP, and Phospholipase A2 (PLA2) activity by measuring the lyso-phosphatidylcholine produced from mast cell prelabeled with 1-palmitoyl-2-arachidonyl phosphatidyl-(14C)choline. Histamine was assayed by fluorometric analyzer, and leukotrienes by radioimmunoassay. The PLC activity was increased by activation of the passively sensitized mast cells. This increased PLC activity was decreased by cromakalim pretreatment. The PKC activity increased by the activation of the passively sensitized mast cells was decreased by calphostin C, staurosporine and cromakalim, respectively. The PLA2 activity was increased in the activated mast cells. The pretreatment of cromakalim did not significantly decrease PLA2 activity. These data show that cromakalim inhibits histamine release by continuously inhibiting signal transduction processes which is mediated via PLC pathway during mast cell activation, but that cromakalim does not affect PLA2 activity related to leukotriene release.
Animals ; Antigen-Antibody Reactions* ; Cromakalim* ; Digestion ; Guinea Pigs* ; Guinea* ; Histamine ; Histamine Release ; Leukotrienes ; Lung* ; Mast Cells* ; Membranes* ; Muscle, Smooth ; Phosphates ; Phospholipases ; Phospholipases A2 ; Protein Kinase C ; Radioimmunoassay ; Signal Transduction ; Staurosporine ; Type C Phospholipases

No abstract available.
Phospholipases* ; Protein Kinase C* ; Protein Kinases* ; Psychotropic Drugs* ; Type C Phospholipases*

No abstract available.
Macrophages* ; Phospholipases A2* ; Phospholipases* ; Tumor Necrosis Factor-alpha*

No abstract available.
Animals ; Glucose* ; Mesangial Cells* ; Phospholipases A2* ; Phospholipases* ; Rats*