Microsomes muscle

Under anaerobic conditions, p,p -DDT is converted to p,p -DDD by reductive dechlorination, a biotransfonnation that occurs postmortem in vertebrate tissues such as liver and muscle and in certain anaerobic microorganisms (Walker and Jefferies 1978). Reductive dechlorination is carried out by reduced iron porphyrins. It is carried out by cytochrome P450 of vertebrate liver microsomes when supplied with NADPH in the absence of oxygen (Walker 1969 Walker and Jefferies 1978). Reductive dechlorination by hepatic microsomal cytochrome P450 can account for the relatively rapid conversion of p,p -DDT to p,p -DDD in avian liver immediately after death, and mirrors the reductive dechlorination of other organochlorine substrates (e.g., CCI4 and halothane) under anaerobic conditions. It is uncertain to what extent, if at all, the reductive dechlorination of DDT occurs in vivo in vertebrates (Walker 1974). 

Fingerlings were injected ip with 14C-labeled PCB mixture at 0.3,1,3,10, and 30 mg PCB/kg BW tissues sampled up to 70 days postinjection At 3 days postinjection high doses of 10 and 30 mg PCB/kg BW caused elevation of liver microsomal monooxygenase activity when maximum tissue concentrations, in mg total PCB/kg FW, were 55 in bile, 12 in blood, 8 in muscle, and 8 in liver. Elevated hepatic microsomal monooxygenase activity with muscle and liver PCB concentrations of >0.3 mg/kg FW, but not 0.25 mg/kg FW 6... 

Sediments and biota collected from the Hersey River, Michigan, in 1978, were heavily contaminated with phenanthrene, benz[a]anthracene, and benzo[a]pyrene when compared to a control site. Elevated PAH concentrations were recorded in sediments, whole insect larvae, crayfish muscle, and flesh of lampreys (family Petromyzontidae), brown trout (Salmo trutta), and white suckers (Catostomus commersoni), in that general order (Black et al. 1981). The polluted collection locale was the former site of a creosote wood preservation facility between 1902 and 1949, and, at the time of the study, received Reed City wastewater treatment plant effluent, described as an oily material with a naphthalene-like odor (Black et al. 1981). In San Francisco Bay, elevated PAH concentrations in fish livers reflected elevated sediment PAH concentrations (Stehr et al. 1997). In Chesapeake Bay, spot (Leiostomus xanthurus) collected from a PAH-contaminated tributary (up to 96 mg PAHs/kg DW sediment) had elevated cytochrome P-450 and EROD activity in liver and intestine microsomes (Van Veld et al. 1990). Intestinal P-450 activity was 80 to 100 times higher in fish from highly contaminated sites than in conspecifics from reference sites intestinal EROD activity had a similar trend. Liver P-450 and EROD activity was about 8 times higher in spot from the contaminated sites when compared to the reference sites. Liver P-450 activity correlated positively with sediment PAH, but intestinal P-450 activity seemed to reflect dietary exposure (Van Veld et al. 1990). The poor correlation between hepatic concentrations of PAHs and P-4501A is attributed to the rapid metabolism of these compounds (van der Weiden et al. 1994). 

Most work on the SR and diseased smooth muscle has concerned vascular smooth muscle in hypertensive animals, and bladders from animal models of outflow obstruction. The tools used to study SR function are mainly indirect, and include recording tension or intracellular [Ca2+] with fluorescent probes, measuring Ca2+ fluxes with 45Ca, and investigating the effects of drugs known to block SERCA or activate store release. More directly, some measurement of the activity of SERCA in microsomal preparations has been undertaken (e.g. Zderic et al 1996). 

Cytochrome P-450 systems are also present in both smooth muscle [54, 5 5] and endothelial [56] cells. In studies of hepatic [57] and aortic [58] microsomes, Bennett and colleagues showed that bioconversion of GTN to GDN was NADPH dependent and was inhibited by the cytochrome P-450 inhibitor, SKF 525A. In hepatic microsomes, moreover, conversion of GTN led to activation of sGC [59]. 

Chung, S-J., Chong, S., Seth, P., Jung, C. Y., Fung, H-L., Conversion of nitroglycerin to nitric oxide in microsomes of the bovine coronary artery smooth muscle is not primarily mediated by glutathione S-transferases. J. Pharmacol.Exp. 

Biochemical studies with mussel tissue homogenates and microsomal fractions have been conducted using viscera (whole mussel minus adductor muscles), green gland, gill, and mantle. Using aerobic conditions and an NADPH-generating system, the metabolism of aldrin and p-nitroanisole have been observed. 

Membrane alanyl aminopeptidase (microsomal aminopeptidase, amino-peptidase M, EC 3.4.11.2) and peptidyl-dipeptidase A (angiotensin I converting enzyme, EC 3.4.15.1) located in the vascular endothelium and smooth muscle cell surface modulate the levels of vasoactive peptides [23], One of the roles of membrane-bound enzymes is to switch off the action of peptides in the vicinity of the target or to prevent them from gaining access to a region containing receptors that are activated only by locally released peptides. 

C8. Coltart, J., Howard, M., and Chamberlain, D., Myocardial and skeletal muscle concentrations of digoxin on long-term therapy. Brit. Med. J. 11, 318-319 (1972). C9. Conney, A. H., Pharmacological implications of microsomal enzyme induction. Pharmacol. Rev. 19, 317-366 (1967). 

Inositol triphosphate is water soluble and therefore diffuses into the cytoplasm, where it mobilizes calcium from its stores in microsomes or the endoplasmic reticulum. The Ca ions then activate Ca-dependent kinases (like troponin C in muscle) directly or bind to the ubiquitous Ca-binding protein calmodulin, which activates calmodulin-dependent kinases. These kinases, in turn, phosphorylate cell-specific enzymes. 

Protection of vascular endothelial cells from oxygen free radical damages Enhancement of SOD, catalase and peroxidase in the cytosol of kidney Protection of pulmonary endothelium against free radicals in rabbits Protection of lipid peroxidation in liver and cardiac muscle in rats Inhibition of lipid peroxidation of rat liver and brain microsomes Inhibition of lipid peroxidation in serum and liver in rats Protective effect of ginsenosides on reperfusion injuries... 

A variety of other calcium transport systems are associated with Ca21-activated ATPases. The extraembryonic structure, the chorioallantoic membrane, of the chick embryo is responsible for the translocation of over 120 mg of eggshell calcium into (he embryo during development. The enzyme responsible for this is a (Ca2+, Mg2+)-ATPase with Km values for Ca2+ of 30 p,mol dm-3 and 0.3 mmol dm-3, and a molecular weight of 170 000. The enzyme can be crossiinked and co-isolated with a calcium-binding protein.158 Transport of Ca2+ is also associated with (Ca2+, Mg2+)-ATPases in neutrophil plasma membranes,159 transverse tubule membranes from rabbit skeletal muscle,160 rabbit myocardial membrane,161 endoplasmic reticulum,162 sar-colemma,163 brain microsomes,164 the Golgi apparatus165 and rat liver plasma membranes.166... 

Most muscle relaxants are absorbed fairly easily from the gastrointestinal tract, and the oral route is the most frequent method of drug administration. In cases of severe spasms, certain drugs such as methocarbamol and orphenadrine can be injected intramuscularly or intravenously to permit a more rapid effect. Likewise, diazepam and dantrolene can be injected to treat spasticity if the situation warrants a faster onset. As discussed earlier, continuous intrathecal baclofen administration may be used in certain patients with severe spasticity, and local injection of botulinum toxin is a possible strategy for treating focal dystonias and spasticity. Metabolism of muscle relaxants is usually accomplished by hepatic microsomal enzymes and the metabolite or intact drug is excreted through the kidneys. 

Intermediate-duration studies have also been conducted with radioactively labeled OCDD. OCDD had similar patterns of distribution and similar half-lives as 2,3,7,8-TCDD in Sprague-Dawley (Norback et al. 1975) and Fischer 344 rats (Bimbaum and Couture 1988 Bimbaum et al. 1989a). Most of the absorbed amount (50-97%) was found in the liver and was associated with the microsomal fractions. Skin- and adipose-tissue levels were much lower. Radioactivity was also detected in the kidneys, heart, testes, skeletal muscle, and serum. 

One of the functions of insulin is to stimulate the movement of glucose into cells. Only a limited number of tissues are sensitive to insulin, however, including the heart, skeletal muscle, and adipose tissue. Liver, kidneys, and brain are not sensitive to insulin, although they contain glucose transporters. Glucose transporters of insulin-sensitive tissues are normally stored in the microsomes... 

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