Effect of Conditioned Ischemic Stresses on NF-kappaB Activation in Rat Skeletal Muscle

OBJECTIVE: To investigate the effect of conditioned ischemic stresses on NF-kappaB activities and the protective role of genistein in rat skeletal muscle. METHOD: Rectus femoris muscles of rats were divided into 4 groups according to conditioned ischemic stresses as followings: sham-operated control group; 2 hour ischemia group by clamping the proximal femoral vessel; ischemia-reperfusion group by 30 minutes of reperfusion following 2 hours of ischemia; ischemia-reperfusion-electrical nerve stimulation group in which current was applied at the femoral nerve during 30 min of reperfusion period to induce repetitive muscle contraction. Either genistein-5% dimethyl sulfoxide (DMSO) or DMSO was injected 2 hours before ischemic induction. NF-kappaB activities were analysed by electrophoretic mobility shift assay. RESULTS: NF-kappaB activities pretreated with DMSO were significantly increased in ischemia, ischemia-reperfusion and ischemia-reperfusion-electrical nerve stimulation group compared with those of control group and in ischemia-reperfusion-electrical nerve stimulation group compared with those of ischemia group. Muscle edema was increased in ischemia-reperfusion-electrical nerve stimulation group. But, NF-kappa activities and muscle edema pretreated with genistein were attenuated in ischemia-reperfusion-electrical nerve stimulation group compared with those pretreated with DMSO alone. CONCLUSION: NF-kappaB activities reflect the severity of ischemic stresses. Pretreatment with genistein can attenuate NF-kappa activities and muscle edema in ischemic stress of rat skeletal muscle.

Comparative effects of PKB- alpha and PKC- zeta on the phosphorylation of GLUT4-containing vesicles in rat adipocytes

Insulin stimulates glucose transport in muscle and fat cells by promoting the translocation of glucose transporter (GLUT4) to the cell surface. Phosphatidylinositide 3-kinase (PI3-kinase) has been implicated in this process. However, the involvement of protein kinase B (PKB)/Akt and PKC- zeta, those are known as the downstream target of PI3-kinase in regulation of GLUT4 translocation, is not known yet. An interesting possibility is that these protein kinases phosphorylate GLUT4 directly in this process. In the present study, PKB- alpha and PKC- zeta were added exogenously to GLUT4-containing vesicles purified from low density microsome (LDM) of the rat adipocytes by immunoadsorption and immunoprecipitation for direct phosphorylation of GLUT4. Interestingly GLUT4 was phosphorylated by PKC- zeta and its phosphorylation was increased in insulin stimulated state but GLUT4 was not phosphorylated by PKB- alpha. However, the GST-fusion proteins, GLUT4 C-terminal cytoplasmic domain (GLUT4C) and the entire major GLUT4 cytoplasmic domain corresponding to N-terminus, central loop and C-terminus in tandem (GLUT4NLC) were phosphorylated by both PKB- alpha and PKC- zeta. The immunoblots of PKC- zeta and PKB- alpha antibodies with GLUT4-containing vesicles preparation showed that PKC- zeta was co-localized with the vesicles but not PKB- alpha. From the above results, it is clear that PKC- zeta interacts with GLUT4-containing vesicles and it phosphorylates GLUT4 protein directly but PKB- alpha does not interact with GLUT4, suggesting that insulin-elicited signals that pass through PI3-kinase subsequently diverge into two independent pathways, an Akt pathway and a PKC- zeta pathway, and that later pathway contributes, at least in part, insulin stimulation of GLUT4 translocation in adipocytes via a direct GLUT4 phosphorylation.

GLUT phosphorylation may be required to GLUT translocation mechanism

In this work, GLUTs phosphorylations by a downstream effector of PI3-kinase, PKC- zeta, were studied, and GLUT4 phosphorylation was compared with GLUT2 phosphorylation in relation to the translocation mechanism. Prior to phosphorylation experiment, PKC- zeta kinase activity was determined as 20.76+/-4.09 pmoles Pi/min/25 ng enzymes. GLUT4 was phosphorylated by PKC- zeta and the phosphorylation was increased on the vesicles immunoadsorpted from LDM and on GLUT4 immunoprecipitated from GLUT4-contianing vesicles of adipocytes treated with insulin. However, GLUT2 in hepatocytes was neither phosphorylated by PKC- zeta nor changed in response to insulin treatment. It was confirmed by measuring the subcellular distribution of GLUT2 based on GLUT2 immunoblot density among the four membrane fractions before and after insulin treatment. Total GLUT2 distributions at PM, LYSO, HDM and LDM were 37.7+/-12.0%, 42.4+/-12.1%, 19.2+/-5.0% and 0.7+/-1.2% in the absence of insulin. Total GLUT2 distribution in the presence of insulin was almost same as that in the absence of insulin. Present data with previous findings suggest that GLUT4 translocation may be attributed to GLUT4 phosphorylation by PKC- zeta but GLUT2 does not translocate because GLUT2 is not phosphorylated by the kinase. Therefore, GLUT phosphorylation may be required in GLUT translocation mechanism.

Study on the action by PAF on IL-1 modulation in alveolar macrophages: Involvement of endogenous arachidonate metabolites and intracellular Ca++ mobilization

Platelet-activating factor (PAF) enhanced interleukin-1 (IL-1) activity by the interaction with a specific receptor in rat alveolar macrophages. In this study, we investigated the role of endogenous arachidonate metabolites and intracellular calcium mobilization in the PAF-induced IL-1 activity. Alveolar macrophages were preincubated with 5-lipoxygenase and cyclooxygenase inhibitors 30 min before the addition of PAF and lipopolysaccharide (LPS). After 24 h culture, IL-1 activity was measured in the supernate of sample using the thymocyte proliferation assay. Inhibition of 5-lipoxygenase by nordihydroguaiaretic acid and AA-861 completely blocked the PAF-induced enhancement of IL-1 activity with IC50 of 2 micrometer and 5 micrometer, respectively. In contrast, the inhibition of cyclooxygenase pathway by indomethacin and ibuprofen resulted in the potentiation in PAF-induced IL-1 activity with maximal effect at 1 micrometer and 5 micrometer, respectively. In addition, leukotriene B4 and prostaglandin E2 production were observed in PAF-stimulated alveolar macrophage culture. As could be expected, 5-lipoxygenase and cyclooxygenase inhibitors abolished PAFstimulated leukotriene B4 and prostaglandin E2 production, respectively. The effects of PAF on intracellular calcium mobilization in alveolar macrophages were evaluated using the calcium-sensitive dye fura-2 at the single cell level. PAF at any dose between 10-16 and 10-8M did not increase intracellular calcium. Furthermore, there was no effective change of intracellular calcium level when PAF was added to alveolar macrophages in the presence of LPS or LPS + LTB4, and 4, 24 and 48h after treatment of these stimulants. Together, the results indicate that IL-1 activity induced by PAF is differently regulated through subsequent induction of endogenous 5-lpoxygenase and cyclooxygenase pathways, but not dependent on calcium signalling pathway.

Effects of nifedipine and captopril on cisplatin induced nephrotoxity in rats / 대한신장학회잡지

No abstract available.

The Study on the Na(+), K(+)-ATPase Activities of the Spontaneously Hypertensive Rats

Although the mechanism of the development of hypertension has not been fully elucidated, abnormal ion transport across the cardiovascular musle membrance may play some role in this mechanism. The elevation of intraceular sodium by inhibition of the Na(+), K(+)-ATPase diminshes the sodium gradient for calcium extrusion and/or increase Na(+)/Ca(++) exchange across the cell membrance. In any event, contractility and vascular tone of cardiovascular system can be incresed as reslut of an increase of intracellular calcium. Recently it is reported that the defects of Na(+), K(+)-ATPase occur in spontaneously hypertensive rat(SHR) hearts, compared to control normotensive Spargue Dawley(SD) rat hearts. However, one missing, unresolved question arose in the previous reports in whether the reduced Na(+)-pump activity in the heart of SHR is associated with the development of hypertension itself in these animals or is a consequence of inhertied pathological features that later reslut in a reduced pump activity. In order to clearify this question it is attempted to measured to measure the change of the Na(+), K(+)-ATPase activities in cardiac sarcolemma purified from both the normotensive SD rats and SHR rats during growth ; Simultaneously the charge of cation concentration in both intracellular space(RBC) and extracelluar space(ECF) are measured to the erythrocyte test(Garay and Meyer) applied to the clinical investiation of hypertension. The results obtained are summarized as follows ; 1) The systolic blood pressure of 7 week old SHR was 120-130mmHg, which was not significantly different from that of the age-matched SD rats. However, the blood pressure was elevated to 160-170mmHg in 13-15 week old SHR, even elevated to 190mmHg in one of 19 week old SHR. On the other hand, SHR, in which hypertension was well established had pronounced cardiac hypertrophy. 2) The Na(+), K(+)-ATPase activities in cardiac sarcolemma of the SHR rats were decreased gradually as hypertension established.The decrease of Na(+), K(+)-ATPase was well associated with the increase of intracellular potassium concentration.By contrast, thr Na(+), K(+)-ATPase activities and cation transports og the normotensive SD rats were not significanlty chaged during growth. 3) The charges of Na(+), K(+)-ATPase activities in SHR were specific because the activities of Ca(++)-ATPase which is one of the membrance bound enzyme were not changed during growth appeared to be a major fator which generated hypertension in SHR rats. However, question on how the Na(+), K(+)-ATPase activities are decreased and which event is initiative between reduction of Na(+), K(+)-ATPase and development of hypertension are still remained unclear. Recent literature suggests the there might be a genetic factor, so-called Na(+)-pump inhibitor, involved in the meachanism.

Effect of Panax Ginseng Alcohol Extract on Cardiovascular System

The effects of the alcohol extract of Panax ginseng on the myocardial contractility particularly with respect to Bowditch and Woodworth phenomena and the norepinephrine induced contraction of the vascular smooth muscle were studied in vitro. 1) In the isolated muscle preparation of guinea pig left auricle, the administration of ginseng-alcohol extract at concentrations of 10~50mg% resulted in a significant reduction of both Bowditch and Woodworth effects. 2) In the isolated Ca++ depleted heart of rabbit ginseng-alcohol extract inhibited the Ca++ uptake and the restoration of contractile force during perfusion with a Ca++ containing solution. 3) In the isolated muscle strip of the rabbit aorta noradrenaline (5 X 10-8 g/ml) induced contraction was inhibited by the ginseng-alcohol extract at concentrations of 10~50mg%. From these results it is speculated that the hypotensive effect of ginseng is accounted for by 1) the direct inhibition of myocardial contractility which is resulted from the reduction of Ca++ influx into cardiac cell, and 2) the inhibition of the catecholamine induced contractility of vascular smooth muscles.

Further Studies on Effects of Some Local Anesthetics on Calcium Binding to Lipid-extracted RBC Membrane Fragments: Effect of Modification of Carboxyl Group with Carbodiimide

The interaction of calcium and local anesthetics was investigated with the lipid extracted human RBC membrane fragments treated with carbodiimide in order to titrate carboxyl groups. A water soluble carbodiimide [1-cyclohexyl-3-(2-morpholinoethyl) carbodiimide methotoluene-p-sulfonate], referred to as a carbodiimide reagent, and glycine methylester were used for this purpose. About 76% of carboxyl groups of the fragments were modified at a concentration of 0.05M carbodiimide reagent. The interaction of calcium and local anesthetics such as procaine and lidocaine with these fragments still showed typical competition. However, when the calcium binding was decreased to 8% at a higher concentration of carbodiimide reagent (0.08M), the local anesthetics still inhibited the calcium binding, but were not competitive in nature. In other words, if concentrations of the carbodiimide reagent were raised, the degree of inhibition by the local anesthetics was gradually decreased and was not competitive in nature. Finally, no inhibition was demonstrated when the concentration of the reagent was 0.1 to 0.4M. The above findings, seem to suggest that local anesthetics such as procaine and lidocaine interact with carboxyl groups, in addition to phosphodiester groups of phospholipids as previously reported, and inhibited competitively calcium binding to carboxyl groups of the membrane fragments.

Further Studies on Effects of Some Local Anesthetics on Calcium Binding to Lipid-extracted RBC Membrane Fragments: Effect of Modification of Carboxyl Group with Carbodiimide

The interaction of calcium and local anesthetics was investigated with the lipid extracted human RBC membrane fragments treated with carbodiimide in order to titrate carboxyl groups. A water soluble carbodiimide [1-cyclohexyl-3-(2-morpholinoethyl) carbodiimide methotoluene-p-sulfonate], referred to as a carbodiimide reagent, and glycine methylester were used for this purpose. About 76% of carboxyl groups of the fragments were modified at a concentration of 0.05M carbodiimide reagent. The interaction of calcium and local anesthetics such as procaine and lidocaine with these fragments still showed typical competition. However, when the calcium binding was decreased to 8% at a higher concentration of carbodiimide reagent (0.08M), the local anesthetics still inhibited the calcium binding, but were not competitive in nature. In other words, if concentrations of the carbodiimide reagent were raised, the degree of inhibition by the local anesthetics was gradually decreased and was not competitive in nature. Finally, no inhibition was demonstrated when the concentration of the reagent was 0.1 to 0.4M. The above findings, seem to suggest that local anesthetics such as procaine and lidocaine interact with carboxyl groups, in addition to phosphodiester groups of phospholipids as previously reported, and inhibited competitively calcium binding to carboxyl groups of the membrane fragments.

Effects of Some Local Anesthetics on Ca++ Binding to Lipid-Extracted RBC Membrane, Egg Albumin Film and Filter Paper

Local anesthetics at a concentration of 10 mM(procaine and lidocaine) were found to inhibit competitively Ca++ binding to lipidextracted RBC membrane, and also to egg albumin film fixed on cover glasses or impregnated into Whatman filter paper (No. 1). A competitive inhibition by local anesthetics was also found in Ca++ binding to Whatman filter paper which had been pretreated with organic solvents to extract possible contaminated lipids. Therefore, it is suggested that the local anesthetics inhibit Ca++ binding not only to phospholipids but to some macromolecules such as membrane proteins, egg albumin film and filter paper.