Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cyclophosphamide (CYC) is a metabolically activated, DNA-alkylating, antitumor agent that causes pulmonary fibrosis. BALB/cN (B) mice are sensitive and C57Bl/6N (C) mice are resistant to CYC-induced fibrosis. Pulmonary bioactivation may contribute to strain sensitivity. Therefore, we tested the intrinsic susceptibility of murine lung slices to cell injury by direct exposure to CYC for 2-8 hr. Injury was measured by release of lactate dehydrogenase (LDH). DNA damage activates the nuclear enzyme poly(ADP-ribose) polymerase (PAP, EC 2.4.2.30), causing depletion of its substrate, NAD. NAD can also be decreased by phosphorylation to NADP, as seen with oxidative stress. Depletion of NAD can lead to loss of ATP. Thus, we measured LDH release, PAP activation, NAD, NADP and ATP in slices incubated with or without the PAP-inhibitor, 3-aminobenzamide (3-AB). CYC (0.1 to 1.0 mg/mL for 4-8 hr) caused LDH release in slices from both murine strains, but LDH release was significantly greater in B lung slices than in C slices. After an 8-hr incubation 63.9 +/- 3.7% (mean +/- SEM) of total LDH was released from B lung slices with 1.0 mg CYC/mL, whereas only 45.8 +/- 2.6% was released from C lung slices (P < 0.05). 3-AB reduced LDH release to 44.7 +/- 2.4% in B slices and 28.1 +/- 2.0% in C slices (P < 0.05 vs CYC only). PAP activity in nuclei isolated from CYC-treated B lung slices was increased 2- to 4-fold after 2 hr of incubation with 0.5 and 1.0 mg CYC/mL. PAP activation was delayed and reduced with incubation in 3-AB. PAP was activated 2-fold in nuclei from C slices treated with 0.5 mg CYC/mL for 2 hr. NAD was decreased at 2 and 4 hr in B slices treated with 0.5 and 1.0 mg CYC/mL, and at 4 hr with 0.1 mg CYC/mL. NAD depletion occurred only at 4 hr in the resistant C slices treated with 1.0 mg CYC/mL. CYC increased NADP by a similar extent in B and C lung slices. In B slices, NAD losses were approximately 4 times the increases in NADP. CYC did not decrease ATP in B slices and ATP dropped 25% only after 4 hr in the resistant C slices. We conclude that CYC is directly toxic to lung tissue and observe that strain sensitivity in vitro mirrors the sensitivity to fibrosis in vivo. PAP activation and oxidative stress may contribute to this toxicity.
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PMID:Acute pneumocyte injury, poly(ADP-ribose) polymerase activity, and pyridine nucleotide levels after in vitro exposure of murine lung slices to cyclophosphamide. 798 Jun 45

On maintenance in supplemented Williams E medium, human hair follicles grow at the normal rate, and retain their normal anagen morphology, for up to 10 days. This permits us to study their metabolism under near-physiological conditions. The ATP content of freshly isolated follicles was 124.4 +/- 10.6 pmol/follicle (mean +/- SEM; n = 50). The energy charge was 0.81 +/- 0.08 and the glycogen content 2.3 +/- 0.3 nmol/follicle. These did not alter significantly during any metabolic studies, which were performed for up to 6 h in supplemented Williams E medium. We found that the major fuel was glucose, which at physiological concentrations yields 5.47 +/- 0.77 nmol ATP/follicle/h, but 90% of the glucose was metabolised to lactate, and only 10% oxidised. Glutamine was also an important fuel, generating 2.16 +/- 0.33 nmol ATP/follicle/h, but this too was largely metabolised to lactate rather than oxidised. Lipid fuels such as palmitate or beta-hydroxybutyrate only yielded 0.72 +/- 0.15 and 0.72 +/- 0.14 nmol ATP/follicle/h, respectively, and their oxidation did not inhibit glucose utilisation. No glucose-fatty acid cycle operates in the hair follicle, therefore, but a glucose-glutamine cycle does, since the presence of glutamine will inhibit glucose utilisation.
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PMID:The human hair follicle engages in glutaminolysis and aerobic glycolysis: implications for skin, splanchnic and neoplastic metabolism. 800 21

We have previously demonstrated (M. Stubbs, Z. M. Bhujwalla, G. M. Tozer, L. M. Rodrigues, R. J. Maxwell, R. Morgan, F. A. Howe, and J. R. Griffiths, NMR Biomed., 5: 351, 1992) that the intracellular pH (pHi) of several rat tumors is higher (> pH 7.0) than that of the tumor extracellular fluid (pHe), in contrast to normal tissues (e.g., liver) in which pHi is lower than pHe. In this paper we confirm a pHe of 6.8 +/- 0.07 (SEM) in Morris hepatoma 9618a by an independent method and report the tissue content of other ions by both 31P magnetic resonance spectroscopy and by conventional analysis in hepatomas and livers in rats. Compared with liver, tissue Na+ was 2-fold higher and tissue K+ was lower. Tissue Ca2+ was 8-fold higher (7.4 +/- 4.3 mumol/g wet weight) and tissue Pi was 2-fold higher (8.5 +/- 1.3 mumol/g wet weight) suggesting the presence of insoluble calcium phosphate. Cl- was unchanged (approximately 40 mumol/g wet weight), whereas HCO3- was lower in the hepatoma (12.4 +/- 0.83 compared to 15.5 +/- 0.76 mumol/g wet weight). Total tissue Mg2+ was similar in both tissues, but free [Mg2+] (calculated by two different methods) was approximately 5-fold lower in the hepatoma. The ATP values were 3.5-fold and [NAD]/[NADH] 9-fold lower in the hepatoma. The results are compatible with the hypothesis that the chronic partial hypoxia of tumor tissue involves changes in the linked equilibria of many ions and metabolites and may help explain such pathologies as calcification.
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PMID:Metabolic consequences of a reversed pH gradient in rat tumors. 803 32

The mechanisms by which ischemic preconditioning (IPC) protects against reperfusion (RP) injury are unknown. The purpose of this study was to relate IPC to postischemic mechanical function, vascular reactivity, and bioenergetics. Isolated perfused rat hearts were randomized to two groups. Control (CTRL) hearts underwent 25 min of global, 37 degrees C ischemia and 40 min RP. IPC hearts underwent 2.5 min ischemia and 10 min RP followed by 25 min ischemia and 40 min RP (RP40). Left ventricular developed pressure (DP) and coronary flow were continuously measured. 31P NMR spectra determined phosphocreatine and ATP concentrations in parallel hearts every 5 min. Results are means +/- SEM; n = 6/group. Significance was assumed for P < 0.05 by paired (within groups) and unpaired (between groups) t test. CTRL heart DP recovered to 35 +/- 4% of preischemic (PI) DP by RP40 (P < 0.001), while IPC heart DP reached 99 +/- 4% (P = NS vs PI; P < 0.001 vs CTRL). CTRL coronary flow recovered to only 75 +/- 3% of PI (P < 0.001) by RP40. IPC coronary flow exceeded baseline during RP (RP40 = 118 +/- 3%, P < 0.001 vs CTRL; P < 0.05 vs PI). After 25 min ischemia, CTRL heart ATP fell to 40 +/- 4% of PI (P < 0.001) while the IPC group fell to only 60 +/- 4% (P < 0.05 IPC vs CTRL; P < 0.001 vs PI). IPC preserves more end-ischemic ATP compared to CTRL hearts with a resultant improvement in mechanical function during reperfusion. Only preconditioned hearts preserve the adaptive mechanism(s) responsible for postischemic vasodilatation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Ischemic preconditioning preserves end-ischemic ATP, enhancing functional recovery and coronary flow during reperfusion. 804 Nov 35

The multidrug-resistant P-glycoprotein (Pgp), a M(r) 170,000 plasma membrane protein encoded by the mammalian multidrug resistance gene (MDR1), appears to function as an energy-dependent efflux pump. Many of the drugs that interact with Pgp are lipophilic and cationic at physiological pH. We tested the hypothesis that the synthetic gamma-emitting organotechnetium complex, hexakis(2-methoxyisobutylisonitrile)technetium(I) ([99mTc]SESTAMIBI), a lipophilic cationic radiopharmaceutical, could be a suitable Pgp transport substrate capable of functional imaging of the MDR phenotype. The cellular pharmacological profile of [99mTc]SESTAMIBI transport was examined in Chinese hamster V79 lung fibroblasts and the 77A and LZ derivative cell lines which express modestly low, intermediate, and very high levels of Pgp, respectively. Steady-state contents of [99mTc]SESTAMIBI in V79, 77A, and LZ cells were 10.0 +/- 0.5 (SEM) (n = 9), 3.6 +/- 0.5 (n = 8), and 0.4 +/- 0.02 (n = 9) fmol.(mg protein)-1 (nMo)-1, respectively, consistent with enhanced extrusion of the imaging agent by Pgp-enriched cells. Maximal doses (> 100 microM) of the multidrug-resistant reversal agents verapamil and cyclosporin A enhanced [99mTc]SESTAMIBI accumulation in V79, 77A, and LZ cells by approximately 10-, 25-, and 200-fold, respectively. The median effective concentration values for tracer accumulation in the presence of verapamil in V79, 77A, and LZ cells were 4, 100, and 200 microM, and those for cyclosporin A were 0.9, 3, and > 25 microM, respectively. Pgp-mediated [99mTc]SESTAMIBI transport occurred against its electrochemical gradient and was found to be ATP dependent displaying an apparent Km of 50 microM. Carrier-added [99Tc]SESTAMIBI was 11- to 13-fold less toxic in multidrug-resistant cells, and inhibited photolabeling of Pgp by [125I]iodoaryl azidoprazosin in a concentration-dependent manner; half-maximal displacement was observed at approximately 100- to 1000-fold molar excess [99Tc]SESTAMIBI. Exploiting the favorable gamma emission properties of 99mTc, functional expression of Pgp was successfully imaged in human tumor xenographs in nude mice with pharmacologically inert tracer quantities of [99mTc]SESTAMIBI. Functional imaging with these organotechnetium complexes may provide a novel mechanism to rapidly characterize Pgp expression in human tumors in vivo, target reversal agents in vivo, and ultimately provide a means to direct patients to specific cancer therapies.
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PMID:Functional imaging of multidrug-resistant P-glycoprotein with an organotechnetium complex. 809 97

Immediately after birth, glycolysis and lactate oxidation are the major source of ATP production in the rabbit heart. Although the ability of heart to oxidize fatty acid increases within days, glucose oxidation rates remain low in the first week after birth. To further examine the changes in energy substrate use in the newborn period, we developed a right and left ventricular isolated working heart model, in which 2-wk-old rabbit hearts were perfused with buffer containing 11 mM glucose, 0.8 mM palmitate, 0.5 mM lactate, and 100 microU/mL insulin. Hearts were perfused at a 7.5 mm Hg left atrial preload, a 4.5 mm Hg superior vena cava preload, a 30 mm Hg aortic afterload, and a 4.5 mm Hg pulmonary artery afterload. Glycolytic rates [measured as 3H2O production from (5-3H)-glucose] were 791 +/- 108 nmol/g dry weight.min-1 (mean +/- SEM). Oxidation rates of glucose, lactate, and palmitate (measured as 14CO2 production from 14C substrates) were 94 +/- 15, 126 +/- 13, and 60 +/- 8 nmol/g dry weight.min-1, respectively. In these hearts, the majority of ATP production derived from exogenous sources was obtained from fatty acid oxidation (52%), whereas 11, 23, and 15% of ATP requirements were derived from glycolysis, glucose oxidation, and lactate oxidation, respectively. These studies demonstrate that by 2 wks of age in rabbits, fatty acids are the major source of energy in the heart. However, although the contribution of glucose oxidation to ATP production has increased compared with 1- or 7-d-old rabbit hearts, glucose oxidation rates are still low compared with adult hearts.
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PMID:The contribution of glycolysis, glucose oxidation, lactate oxidation, and fatty acid oxidation to ATP production in isolated biventricular working hearts from 2-week-old rabbits. 810 85

Effects on isometric tension generation and maximum velocity of unloaded shortening after exposure to cAMP-dependent protein kinase (PKA) were investigated in rat enzymatically isolated, tritonized ventricular myocytes. Exposure of myocytes to PKA in the presence of [32P]ATP resulted in phosphorylation of troponin I and C protein. Ca2+ sensitivity of isometric tension was assessed as pCa50, ie, the [Ca2+] at which tension was 50% of maximum, and was lower after PKA treatment (pCa50 5.58) than before PKA treatment (pCa50 5.74). This suggests beta-adrenergic stimulation of the heart and subsequent increases in PKA activity and phosphorylation of troponin I and C protein lead to a significant decrease in tension-generating ability at a given submaximum [Ca2+]. Unloaded shortening velocity was determined by measuring the time required to take up various amounts of slack imposed at one end of the cardiac myocyte preparation. Unloaded shortening velocity during maximum activation was 2.88 +/- 0.11 muscle lengths per second (mean +/- SEM) before PKA exposure and 2.86 +/- 0.13 muscle lengths per second after PKA exposure. Unloaded shortening velocity during 40% of maximum activation was 1.91 +/- 0.25 muscle lengths per second before PKA exposure and 2.17 +/- 0.15 muscle lengths per second after PKA exposure. The absence of an effect of PKA on unloaded shortening velocity in skinned ventricular myocytes suggests that beta-adrenergic stimulation of myocardium either does not affect myofilament velocity of shortening or alters velocity of shortening by a non-PKA-dependent process.
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PMID:Effects of phosphorylation of troponin I and C protein on isometric tension and velocity of unloaded shortening in skinned single cardiac myocytes from rats. 813 7

We tested the hypothesis that dilatation of cerebral arterioles during hypoxia is mediated by activation of ATP-sensitive K+ channels. The diameter of pial arterioles was measured through a closed cranial window in anesthetized rabbits. Topical application of aprikalim (10(-6) mol/L), a direct activator of ATP-sensitive K+ channels, dilated pial arterioles by 18 +/- 3% (mean +/- SEM). Glibenclamide (10(-6) mol/L), an inhibitor of ATP-sensitive K+ channels, virtually abolished aprikalim-induced vasodilatation. When arterial PO2 was reduced from 129 +/- 3 to 25 +/- 1 mm Hg, the diameter of cerebral arterioles increased by 66 +/- 9% (P < .05). Glibenclamide inhibited dilatation of pial arterioles during hypoxia by 46 +/- 5% (P < .05). In contrast, vasodilatation in response to sodium nitroprusside was not altered by glibenclamide. Topical application of adenosine (10(-4) mol/L) increased arteriolar diameter by 21 +/- 4%. Glibenclamide did not affect adenosine-induced vasodilatation. These findings suggest that dilatation of cerebral arterioles in response to hypoxia is mediated, in part, by activation of ATP-sensitive K+ channels.
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PMID:ATP-sensitive K+ channels mediate dilatation of cerebral arterioles during hypoxia. 815 23

Differences in purine metabolism produced by three preservation solutions were studied by determining the adenine nucleotide (ATP, ADP, AMP, and IMP) and nucleoside (adenosine, inosine, and hypoxanthine) levels in human kidney cortical biopsies. Forty kidney allografts were studied using University of Wisconsin (UW) solution (n = 20), Euro-Collins (EC) solution (n = 12), and modified EC solution with mannitol (M; n = 8). No significant differences were found between the three solutions studied with regard to ATP, ADP, or AMP changes. The mean ATP level (nmol/mg prot +/- SEM) at the end of preservation in the UW group was 2.7 +/- 0.3 nmol/mg, in the EC group 3.8 +/- 0.7 nmol/mg, and in the M group 2.3 +/- 0.4 nmol/mg. ATP 30 min after reperfusion in the UW, EC, and M groups was 5.7 +/- 0.8 nmol/mg, 6.4 +/- 1.0 nmol/mg, and 4.6 +/- 0.5 nmol/mg, respectively. However, an important difference appeared in the catabolic products determined. Kidneys perfused with UW solution had a significantly higher level of adenosine (2.6 +/- 0.6 nmol/mg), inosine (11.8 +/- 2.2 nmol/mg), and hypoxanthine (18.1 +/- 2.1 nmol/mg) at the end of cold storage than those perfused with EC (0.4 +/- 0.1 nmol/mg, 2.0 +/- 0.8 nmol/mg, and 7.1 +/- 1.4 nmol/mg) and M solutions (0.2 +/- 0.05 nmol/mg, 0.5 +/- 0.1 nmol/mg, and 5.2 +/- 0.6 nmol/mg; P < 0.05). These levels returned to initial values 30 min postreperfusion and there were no differences with the EC or M solution groups at that time.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of different preservation solutions on adenine nucleotide content and metabolism in human kidney transplantation. 817 10

We examined the hypothesis that dilatation of the basilar artery in response to activation of ATP-sensitive potassium channels is impaired in stroke-prone spontaneously hypertensive rats (SHRSP). Changes in basilar artery diameter in response to aprikalim, a direct activator of ATP-sensitive potassium channels, were measured in anesthetized SHRSP and normotensive Wistar-Kyoto (WKY) rats through a cranial window. Topical application of aprikalim increased basilar artery diameter in WKY rats. Glibenclamide, a selective inhibitor of ATP-sensitive potassium channels, abolished aprikalim-induced vasodilatation. Thus, ATP-sensitive potassium channels are functional in the basilar artery of WKY rats in vivo. Aprikalim (10(-6) mol/L) dilated the basilar artery by 31 +/- 5% (mean +/- SEM) in WKY rats but only 5 +/- 1% in SHRSP. The concentration-response curve to aprikalim in SHRSP was significantly shifted to the right, but the response to the highest concentration of aprikalim (10(-5.5) mol/L) was similar in SHRSP and WKY rats. Vasodilatation in response to norepinephrine was also impaired in SHRSP. Dilator responses of the basilar artery to forskolin, a direct activator of adenylate cyclase, and nitroprusside, a direct activator of guanylate cyclase, were normal in SHRSP. The findings suggest that dilatation of the basilar artery in response to direct activation of ATP-sensitive potassium channels is impaired in SHRSP compared with WKY rats in vivo.
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PMID:ATP-sensitive potassium channels in the basilar artery during chronic hypertension. 822 27


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