Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

EGF has been reported to promote oocyte maturation in several species, although the mechanism of action is not yet known. The present study is designed to determine the pathway used by EGF to enhance porcine oocyte maturation. Oocytes were aspirated from 2-5 mm follicles and cultured with various treatments in Medium-199 at 37 degrees C, 100% relative humidity, and 5% CO2 for 48 hr for the maturation study and 3 hr for intracellular cAMP measurement. Although treatment with 100 IU/ml hCG stimulated both intracellular cAMP formation and oocyte maturation, 10 ng/ml EGF stimulated oocyte maturation only. Dibutyryl cAMP (dbcAMP) inhibited oocyte maturation at 10(-5), 10(-4), and 10(-3) M concentration s in the control medium. However, in the presence of 10 ng/ml EGF, dbcAMP inhibited oocyte maturation only at a concentration of 10(-3) M. Increasing concentrations of EGF (i.e., 25 and 50 ng/ml) were ineffective in overcoming the inhibitory effect of dbcAMP at 10(-3) M. In contrast, EGF reversed the decreased maturation rate caused by transforming growth factor-beta. Phorbol myristate acetate (PMA), a tumor-promoting phorbol ester, enhanced the spontaneous maturation rate; 4 alpha-phorbol dideconoate, an inactive phorbol ester, did not show this effect. PMA- and EGF-stimulated porcine oocyte maturation is reversed by calphostin-C, a PKC inhibitor. In conclusion, EGF's promotional activity on porcine oocyte maturation is independent of the cAMP pathway and probably mediated by the PKC pathway.
 ...
PMID:Mechanism of action of epidermal growth factor-induced porcine oocyte maturation. 857 45

A correlation of the levels of epidermal protein kinase C (PKC) isozymes, steady state levels of ornithine decarboxylase (ODC) mRNA, and ODC antizyme with the induction of ornithine decarboxylase (ODC) activity by a second repeat 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment to mouse skin was determined. A single application of TPA to female CD-1 mouse skin leads to a dramatic induction of ODC activity (approximately 3 nmol CO2/60 min/mg protein) which peaks at about 5 h after treatment. However, a superinduction of ODC activity (approximately 13 CO2/60 min/mg protein) is observed upon the second TPA application at 48 or 72 h after the first TPA treatment. Prior application of a tumor initiating dose of 7,12-dimethylbenz[a]anthracine to mouse skin did not influence the degree of induction of ODC by a repeat TPA treatment. Western Blot analyses using antibodies specific to PKC alpha, beta, gamma, delta and epsilon indicate detectable levels of PKC alpha, beta, delta and epsilon in mouse epidermal extracts. A time course of the effects of a single topical application of 20 nmol of TPA to the mouse skin indicate that none of PKC isozymes (alpha, beta, gamma, delta and epsilon) were completely downregulated at times (72 h) when ODC was overinduced by TPA. TPA-induced steady state levels of ODC mRNA did not correlate with the degree of superinduction of ODC activity by TPA. The second TPA treatment, 72 h after the first TPA treatment, which leads to superinduction of ODC activity did not decrease the levels of the ODC-antizyme. The results indicate that superinduction of mouse epidermal ODC activity is regulated in part post-transcriptionally and may not be the result of either a loss of PKC isoform(s) or a decrease in the levels of ODC antizyme.
 ...
PMID:Superinduction of mouse epidermal ornithine decarboxylase activity by repeated 12-o-tetradecanoylphorbol-13-acetate treatments. 870 Jan 59

This study was designed to determine the effects of concanavalin A (ConA) (a T-cell mitogen) and phorbol myristate acetate (PMA) (an activator of protein kinase C) plus ionomycin (Iono) on glutamine metabolism and proliferation of porcine intestinal intraepithelial lymphocytes (IEL). IEL were prepared from jejunum of 29-day-old pigs weaned at 21 days of age. Cells were cultured at 37 degrees C for 48 hr in RPMI-1640 medium containing 10 mM D-glucose, 0 to 4 mM L-glutamine, 0 to 5 micrograms/ml ConA, or 20 ng/ml PMA + 375 ng/ml Iono. The medium was also supplemented with 0 or 0.1 mM adenosine, guanosine, inosine, uridine or cytosine to study the effect of nucleosides or bases on IEL proliferation. IEL proliferation was assessed by pulsing with 3H-thymidine for 18 hr. Glutamine metabolism was studied in incubated IEL in the presence of Krebs-Henseleit bicarbonate buffer containing 5 mM D-glucose and 1 mM L-[U-14C]glutamine. PMA+Iono markedly stimulated 3H-thymidine incorporation and glutamine metabolism to ammonia, glutamate, aspartate and CO2. When stimulated by PMA+Iono, rates of 3H-thymidine incorporation and glutamine metabolism were much lower in IEL than in mesenteric lymph node lymphocytes. Glutamine was required for IEL proliferation, and it could not be replaced by adenosine, guanosine, inosine, uridine or cytosine, suggesting that porcine IEL cannot interconvert purine and pyrimidine nucleotides. Porcine IEL poorly or not at all responded to ConA stimulation, in contrast to lymph node lymphocytes, in terms of both [3H]thymidine uptake and glutamine metabolism.
 ...
PMID:Effects of concanavalin A and phorbol myristate acetate on glutamine metabolism and proliferation of porcine intestinal intraepithelial lymphocytes. 875 85

1. Brief exposure of cultured rat glomerular mesangial cells (GMC) to H2O2 in nominally bicarbonate-free solution induced a rapid dose dependent, dantrolene-inhibitable increase in intracellular free Ca2+ from 65 +/- 6 to 203 +/- 14 nmol/L and a prolonged release of [14C]-arachidonic acid [14C]-AA which preceded the onset of cell membrane damage assessed by trypan-blue uptake. 2. Ca2+ responses were potentiated in HCO3-/CO2 containing buffers and reached values of 1145 +/- 100 nmol/L at 1 mmol/L H2O2. In HCO3-/CO2 solutions, but not HEPES buffer, H2O2-induced Ca2+ increases were markedly attenuated by verapamil (100 mumol/L) or removal of extracellular calcium. 3. Enhanced release of [14C]-AA was partially attenuated by inhibitors of key intracellular signalling mechanisms including the phospholipase-A2 (PLA2) inhibitor mepacrine (100 mumol/L), the NADPH oxidase inhibitor diphenyliodonium (10 mumol/L), the mitochondrial calcium-cycling inhibitor ruthenium red (10 mumol/L) and the iron chelator dipyridyl (100 mumol/L). Release was unaffected by protein kinase C inhibition with H7 (100 mumol/L), inositol triphosphate antagonism with neomycin (1 mmol/L) or overnight treatment with the G-protein antagonist pertussis toxin (5 micrograms/mL). 4. Several structurally diverse lipoxygenase inhibitors, including esculetin, baicalein and phenidone, over the dose range 1-100 mumol/L, also prevented [14C]-AA release and markedly protected against cell membrane damage. No drug directly scavenged H2O2 assessed by UV absorption. 5. These results indicate that H2O2 activates in GMC a complex series of interrelated pathological mechanisms which in turn contribute to a prolongation of oxidative damage beyond the time of the initial exposure. These include an increase in intracellular calcium which, depending upon conditions, appears to be mediated by release from intracellular stores as well as Ca2+ entry from the extracellular space. In turn there is a sustained release of arachidonic acid, which may partly depend on prolonged activation of PLA2 but not phospholipase C. 6. Release of [14C]-AA could be attenuated by inhibitors of NADPH oxidase, mitochondrial calcium-cycling, iron chelators and a structurally diverse range of lipoxygenase inhibitors in association with protection from H2O2-mediated cell membrane damage.
 ...
PMID:Role of intracellular signalling pathways in hydrogen peroxide-induced injury to rat glomerular mesangial cells. 884 14

We determined the vascular and airway effects of PGF2 alpha and its mechanism of action on isolated-perfused lungs of rats were isolated and perfused at 50 ml/kg/min with Krebs-Henseleit bicarbonate buffer solution containing 3% bovine serum albumin. The lungs were ventilated with 21% O2 and 5% CO2 at a tidal volume of 2 ml. frequency of 60 per minute and positive end expiratory pressure of 3 cmH2O. Following injection of 50 micrograms PGF2 alpha into the afferent pulmonary catheter, there was a marked rise in pulmonary arterial pressure (Ppa) and in resistance to airflow across the lung (RL) and a fall in dynamic lung compliance (Cdyn). Double vascular occlusion technique revealed that 29% of the rise in Ppa was due to an increase in upstream and 71% to downstream resistance. N omega-nitro-L-arginine, 100 microns, a NO synthase inhibitor potentiated the Ppa response two-fold with significant change in airway mechanics. Rat atrial natriuretic factor (r-ANF), 40 micrograms quickly reversed the changes in Ppa, RL and Cdyn. Infusion of r-ANF prior to PGF2 alpha attenuated the Ppa response by 38%, RL by 44% and Cdyn by 12%. SQ 29548, a thromboxane receptor blocker and Cl, a protein kinase C (PKC) inhibitor, fully blocked both the vascular and airway responses to PGF2 alpha. PGF2 alpha is a constrictor of pulmonary vessels and airways in rat lungs via thromboxane SQ 29548 receptors, thansduced by intracellular PKC.
 ...
PMID:PGF2 alpha causes bronchoconstriction and pulmonary vasoconstriction via thromboxane receptors in rat lung. 888 79

The purpose of the present study was to assess the effects of hypoxia/reoxygenation (H/R) on vasoconstrictor effectiveness, in vitro. Aortic rings were obtained from rats and placed on isometric force transducers in oxygenated Krebs buffer (95% O2/5% CO2, PO2 > 500 torr). Cumulative concentration/effect relationships to norepinephrine, G-protein activation by AlICl3/NaF, depolarization by KCl or BayK-8644, mobilization of intracellular calcium by caffeine, and protein kinase C activation by l-indolactam were evaluated. Hypoxia (PO2 < 5 torr) was induced by rapidly bubbling the Krebs buffer with 95% N2/5% CO2 for 15 min. Vessel rings were reoxygenated for 30 min and concentration/effect relationships reevaluated. The dissociation constant (KA) for norepinephrine was also determined. The pD2 for maximal norepinephrine responsiveness decreased from 7.7 to 7.3 following H/R. Maximal tension generation was significantly decreased following H/R. Endothelium denudation or nitric oxide synthesis inhibition did not prevent the right shift in norepinephrine concentration/effect relationship caused by H/R. The combination of superoxide dismutase and catalase prevented the dextral shift in the concentration/effect curve. The dissociation constant for norepinephrine increased from 0.16 to 0.32 microM following H/R, suggesting decreased affinity of adrenergic receptor. H/R did not alter AlCl3/NaF, KCl, BayK-8644 or l-indolactam-induced vasoconstriction. Caffeine-induced vasoconstriction was significantly impaired following H/R, suggesting that release of calcium from the sarcoplasmic reticulum is compromised. These results suggest that H/R leads to an endothelium independent, oxidant-mediated decrease in vascular norepinephrine responsiveness that may be related to defects in the mobilization of intracellular calcium from the sarcoplasmic reticulum pool.
 ...
PMID:Effects of hypoxia/reoxygenation on aortic vasoconstrictor responsiveness. 889 62

The distribution of pH-regulating transporters in surface and transverse (T) tubular membrane (TTM) domains of frog skeletal muscle was studied. 2',7'-Bis(carboxyethyl)-5(6)- carboxyfluorescein-loaded giant sarcolemmal vesicles, containing surface membrane, exhibited reversible Na+/H+ exchange. A microsomal vesicle fraction was shown to be enriched in TTM on the basis of high Na(+)-K(+)-ATPase and Mg(2+)-ATPase activity, high ouabain and nitrendipine binding, and low Ca(2+)-ATPase activity. TTM vesicles were well sealed and oriented inside out. Vesicles were loaded with the pH-sensitive dye pyranine. In response to an inwardly directed Na+ gradient, vesicles displayed virtually no alkalinization unless monensin was present. No pH response to an imposed Na+ gradient was seen regardless of the direction of the pH gradient across the vesicles, after phosphorylation of the vesicles with protein kinase C, or when exposed to guanosine 5'-O-(3-thiotriphosphate). In the presence of CO2, addition of Na+ or Cl- had no effect on vesicle pH. These data indicate that the TTM lacks functional pH-regulating transporters [Na+/H+ and (Na+ + HCO3-)/Cl- exchangers], suggesting that pH-regulating transporters are localized only to the surface membrane domain in frog muscle.
 ...
PMID:Membrane domain localization of pH-regulating transporters in frog skeletal muscle membrane vesicles. 889 44

Glutamate-induced neurotoxicity was examined in cultured rat cortical cells. Primary cultures were obtained from the cerebral cortex of fetal rats (17-19 days of gestation). Single cells dissociated from the cerebral cortex were plated on plastic coverslips placed in 35- or 60-mm culture dishes. Cultures were incubated in Eagle's minimal essential medium supplemented with 10% fetal calf serum or 10% horse serum at 37 degrees C in a humidified 5% CO2 atmosphere for 10-14 days. The neurotoxicity induced by glutamate was quantified by trypan blue exclusion. The viability of cultures was markedly reduced by a 10-min exposure to glutamate followed by incubation with glutamate-free medium for 1-24 hr. Glutamate neurotoxicity was prevented by the N-methyl-D-aspartate (NMDA) receptor antagonists, MK-801, 3-[(+/-)-2-carboxypiperazin-4-yl] propyl-1-phosphoric acid (CPP), ifenprodil and 7-Cl-kinurenate. Glutamate neurotoxicity was augmented by phorbol dibutyrate, that activates protein kinase C (PKC), but reduced by H-7, that inhibits PKC. These results suggest that PKC plays an important role in NMDA receptor-mediated glutamate neurotoxicity in the cerebral cortex.
 ...
PMID:[Experimental techniques for developing new drugs acting on dementia (11)--Experimental methods on glutamate neurotoxicity]. 890 96

The signal transduction pathway of hypoxic pulmonary arterial contraction has not been elucidated. Phosphorylation of the 20-kDa myosin light chain (MLC20) is thought to be essential for vascular muscle contraction. However, there are reports that smooth muscle will contract in response to nonphysiological stimuli such as phorbol esters without the involvement of MLC20 phosphorylation. The purpose of this study was to determine if hypoxia-induced pulmonary arterial contraction is dependent on MLC20 phosphorylation. Isolated rat pulmonary and carotid (for comparative purposes) arterial strips were contracted with 80 mM KCl to establish maximum active tension in response to membrane depolarization. The strips were then stimulated with one of the following: 30 mM KCl, 1 microM phenylephrine, 0.01 microM angiotensin II, 1 microM phorbol 12-myristate 13-acetate (PMA), or hypoxia (95% N2-5% CO2). In some experiments ML-9, a myosin light chain kinase inhibitor, or calphostin C, a protein kinase C (PKC) inhibitor, was introduced into the bath before hypoxia. Isometric tension was recorded as a function of time. Muscle strips were freeze-clamped (liquid N2) at various time points during the course of responses to the various stimuli. MLC20 phosphorylation levels were measured by ureaglycerol gel electrophoresis followed by Western blot procedure. Results show that increased MLC20 phosphorylation correlates with initiation of pulmonary arterial smooth muscle contraction in response to all agonists with the exception of PMA, a known activator of PKC. The MLC20 phosphorylation levels correlate with tension development in response to hypoxia, and ML-9 abolished the hypoxic contractions. In contrast, hypoxia relaxed carotid arterial muscle, and there was a corresponding decrease in the MLC20 phosphorylation level. In conclusion, hypoxia appears to result in MLC20 phosphorylation-mediated contraction in conduit pulmonary arterial muscle and in MLC20 dephosphorylation-mediated relaxation in systemic arterial muscle.
 ...
PMID:Hypoxia-induced pulmonary arterial contraction appears to be dependent on myosin light chain phosphorylation. 894 20

Roles of Ca2+ and protein kinase C (PKC) in the regulation of acid/base transport in isolated rabbit proximal tubules were investigated by measuring cytosolic Ca2+ concentrations ([Ca2+]i) and cell pH (pHi) with fluorescent probes. Ionomycin (0.2 microM) increased [Ca2+]i by approximately 200 nM but did not affect the basolateral Na(+)-HCO3- cotransporter. However, the apical Na+/H+ exchanger was inhibited by 50% by ionomycin, and this inhibition was abolished either by 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, an intracellular Ca2+ chelator, or by KN-62, an inhibitor of calcium-calmodulin-dependent protein kinase II (CaM kinase II). On the other hand, phorbol 12-myristate 13-acetate (PMA, 0.5 microM) did not affect the apical Na+/H+ exchanger but did stimulate the basolateral Na(+)-HCO3- cotransporter by 60-80%, and this stimulation was prevented by calphostin C, an inhibitor of PKC. Consistent with the cotransporter stimulation, PMA decreased steady-state pHi in the presence of CO2/ HCO3-. These results indicate that 1) the acute increase in [Ca2+]i within physiological ranges inhibits the apical Na+/H+ exchanger, probably through mediation of CaM kinase II; and 2) the short-term PKC activation stimulates the basolateral Na(+)-HCO3- cotransporter.
 ...
PMID:Roles of Ca2+ and PKC in regulation of acid/base transport in isolated proximal tubules. 894 2


<< Previous 1 2 3 4 5 6 7 Next >>