Active secretion

The thia2ides are actively secreted into the proximal tubules, where they exert their action on the luminal side of the tubules. The diuretic effect occurs within 1 h after oral adininistration, and the duration of action varies from 4 to 24 h depending on which thia2ide-type diuretic is used. The diuretic effects of the thia2ides are not influenced by acid—base conditions of the blood or urine. Probenecid, which also is secreted into the proximal tubules, may block the diuretic effects of the thia2ides. 

The synthesis of dextromethorphan is an outgrowth of early efforts to synthesize the morphine skeleton. /V-Methy1morphinan(40) was synthesized in 1946 (58,59). The 3-hydroxyl and the 3-methoxy analogues were prepared by the same method. Whereas the natural alkaloids of opium are optically active, ie, only one optical isomer can be isolated, synthetic routes to the morphine skeleton provide racemic mixtures, ie, both optical isomers, which can be separated, tested, and compared pharmacologically. In the case of 3-methoxy-/V-methylmorphinan, the levorotatory isomer levorphanol [77-07-6] (levorphan) was found to possess both analgesic and antitussive activity whereas the dextrorotatory isomer, dextromethorphan (39), possessed only antitussive activity. Dextromethorphan, unlike most narcotics, does not depress ciUary activity, secretion of respiratory tract fluid, or respiration. 

Total pectinase, cellulase and lipase activities secreted by colonies were detected on BSM plates containing respectively 1% of citrus pectin, 2% Walseth cellulose and 1% olive oil + rhodamine. After few days at 30°C, pectin plates were covered by 1% CTAB for Ihour, positive colonies became surrounded by a clear halo walseth plates are not stained the halo is visible directly on positive clones lipase activity is revealed under UV on oil-rhodamine plates. 

These agents have broad-spectrum activity against both gram-negative and gram-positive bacteria. They provide high urine and tissue concentrations and are actively secreted in reduced renal function. Switch to oral when possible due to excellent bioavailability. 

J Wacher, L Salphati, LZ Benet. Active secretion and enterocyte drug metabolism barriers to drug absorption. Adv Drug Del Rev 20 99-112, 1996. 

Several studies in rats have shown that certain acidic and basic compounds can be actively secreted into the bile. Thus, one might expect to see saturation of the biliary excretion process, although data in humans describing this phenomenon have not, as yet, been reported for orally dosed drugs. 

The CSF flows through the ventricles, downward through the central canal of the spinal cord, and then upward toward the brain through the subarachnoid space that completely surrounds the brain and spinal cord. As the CSF flows over the superior surface of the brain, it leaves the subarachnoid space and is absorbed into the venous system. Although CSF is actively secreted at a rate of 500 ml/day, the volume of this fluid in the system is approximately 140 ml. Therefore, the entire volume of CSF is turned over three to four times per day. 

Intravenous administration 7 d Nontoxic Renal clearance No active secretion [124]... 

X. Liu, and L. Z. Benet. Contributions of saturable active secretion, passive transcellular, and paracellular diffusion to the overall transport of furosemide across adenocarcinoma (Caco-2) cells,/. Pharm. Sci. 2002,... 

The drawback of this approach is that it is essentially empirical, and does not allow for differences in metabolic clearance between the species, i.e., it assumes that clearance is proportional to blood flow. This works well for compounds that are highly extracted in the liver, and/or where passive renal clearance is the major pathway [5, 68]. An approach for compounds that are actively secreted into the urine has also been proposed [69], although the precise values of some of the physiological scaling factors have been questioned [70]. 

Terao, T., Hisanaga, E., Sai, Y., Tamai, I., Tsuji, A., Active secretion of drugs from the small intestinal epithelium in rats by P-glycoprotein functioning as an absorption barrier,... 

Martin, T. F. J. and Walent, J. H. A new method for cell per-meabilization reveals a cytosolic protein requirement for Ca2+-activated secretion in GH3 pituitary cells. /. Biol. Chem. 264 10299-10308,1989. 

Hay, J. C. and Martin, T. F. I. Phosphatidylinositol transfer protein required for ATP-dependent priming of Ca2+-activated secretion. Nature 366 572-575,1993. 

Patients should be instructed to take oral PPIs in the morning 15 to 30 minutes before breakfast to maximize efficacy, because these agents inhibit only actively secreting proton pumps. If dosed twice daily, the second dose should be taken approximately 10 to 12 hours after the morning dose and prior to a meal or snack. 

The relatively slow phosphorylation of the 78 kDa band in response to either peptide stimulation or to the addition of DSCG suggests that this particular protein band may be involved in the termination of non-immunologically activated secretion [211-214],... 

Free energy (G) is used to perform useful biological work such as active secretion, muscle contraction, powering biosyntheses. 

Zakelj S, Sturm K, Kristi A (2006) Ciprofloxacin permeability and its active secretion through rat small intestine in vitro. Int J Pharm 313 175-180. 

Release from bacteria During cell fission (small amounts) during bacterial cell death (large amounts), which includes lysis during antibiotic treatment Active secretion by growing bacteria... 

Absorption of water and Na+ from the lumen, concentrating the fecal content, and secretion of and HCOs [5]. The active secretion of K+ is stimulated by mineralo-corticoids. 

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