Michaelis-menten absorption kinetics in drugs: ? Examples and implications

Wood, John H.; Thakker, Kamlesh M.

doi:10.1007/bf00545976

Cited by 22 publications

(15 citation statements)

References 26 publications

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“…5). When (21), including modification of monoamine turnover (42)(43)(44), and might trigger control mechanisms regulating enkephalin release (8,9). YGG does not arise from YGGFM selectively, since both the substrate specificity of enkephalinase (30)(31)(32)(33) and release experiments from brain slices (52) for about half the total YGGFM degradation (15).…”

Section: Resultsmentioning

confidence: 99%

Steady-state level and turnover rate of the tripeptide Tyr-Gly-Gly as indexes of striatal enkephalin release in vivo and their reduction during pentobarbital anesthesia.

Llorens-Cortes¹,

Gros²,

Schwartz³

1986

Proc. Natl. Acad. Sci. U.S.A.

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Communicated by E. Costa, April 7, 1986 ABSTRACT Tyr-Gly-Gly (YGG) was recently shown to be an extraneuronal metabolite of opioid peptides derived from proenkephalin A, formed in brain by the action of "enkephalinase" (membrane metalloendopeptidase, EC 3.4.24.11) and degraded by aminopeptidases. The dynamic state of YGG in mouse striatum was studied by evaluating the changes in its level elicited by inhibitors of these peptidases. Inhibition of YGG synthesis by Thiorphan or acetorphan reduced YGG levels with a til2 (mean ± SEM) of 12 ± 2 min, indicating an apparent turnover rate (mean ± SEM) of 18 ± 2 pmol/mg of protein per hr. An apparent turnover rate of 18 ± 2 pmol/mg of protein per hr was derived from the rate of YGG accumulation elicited by the aminopeptidase inhibitor bestatin. In addition, accumulation of Tyr-Gly-Gly-Phe-Met (YGGFM) in an extrasynaptosomal fraction after blockade ofits degradation by Thiorphan and bestatin occurred at a rate of 18 ± 3 pmol/mg of protein per hr, which is likely to reflect the rate of enkephalin release in vivo. Hence, the three series of data suggest that striatal enkephalins rapidly turn over-e.g., with

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Section: Resultsmentioning

confidence: 99%

Steady-state level and turnover rate of the tripeptide Tyr-Gly-Gly as indexes of striatal enkephalin release in vivo and their reduction during pentobarbital anesthesia.

Llorens-Cortes¹,

Gros²,

Schwartz³

1986

Proc. Natl. Acad. Sci. U.S.A.

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“…28 The absorption of chlorothiazide has been shown to be interpretable in terms of Michaeles-Menten-type kinetics, but this does not describe the underlying mechanisms involved. 29 Although limited absorption of chlorothiazide is generally interpreted in terms of absorption site specificity, and a possible absorption ~i n d o w , '~. '~, '~ it may also be explained in terms of limited aqueous solubility.…”

Section: Absorptionmentioning

confidence: 99%

Pharmacokinetics of the thiazide diuretics

Welling¹

1986

Biopharm & Drug Disp

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“…Analyses of dose-response curves were performed using SigmaPlot 11.0 with the Enzyme Kinetics Module to fit data according to the Michaelis-Menten equation (Wood and Thakker, 1982). For this study, this is described as…”

Section: Dose-response and Adsorption Assaysmentioning

confidence: 99%

“…The intrinsic clearance (CL int ) is the ratio of V max /K m that relates the rate of metabolism to the unbound concentration at the enzyme site. For the purposes of this study, the ratio of B max /K relates the adsorption of an adsorbate to the unbound adsorbate in solution, known as the intrinsic adsorption (Ad int ; Wood and Thakker, 1982). Kinetic parameters were compared by ANOVA using SAS (SAS Institute, Cary, NC, USA).…”

Section: Dose-response and Adsorption Assaysmentioning

confidence: 99%

In vitro assessment of the effectiveness of non-nutritive sorbent materials as binding agents for boar taint compounds

Jen

Squires

2011

Animal

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Boar taint, an off-odor and an off-flavor in the meat from some uncastrated male pigs, is due to high levels of the testicular steroid hormone, androstenone, and the indole, skatole. Thus far, there are no known methods for controlling both androstenone and skatole through dietary means. We tested the adsorbent agents, cholestyramine (CH), activated carbon (AC), tween-60 (Tween), bentonite (BNT) and polyvinylpolypyrrolidone (PVPP) for binding androstenone, estrone (E 1 ), estrone sulfate (E 1 S) and skatole from buffer solutions in an in vitro system. The goal was to determine the potential utility of these binding agents as feed additives to control boar taint. Michaelis-Menten analysis was utilized to determine the effectiveness of the adsorbents. At pH 7.4, E 1 S was bound to AC and CH with the highest B max (maximum binding), whereas Tween and AC had the greatest B max for E 1 . The B max for skatole at pH 7.4 was highest for AC, CH and PVPP. AC had a higher B max for androstenone than CH and Tween. The B max values at pH 3.0 with E 1 S for AC and CH were essentially 100%, whereas the binding of Tween to E 1 S at pH 3.0 decreased by 49.5% from binding at pH 7.4 (P , 0.05). The Ad int values, which represent efficiency of binding, illustrated that AC bound E 1 , androstenone and skatole with greater efficiency than the other binding agents at pH 7.4, whereas AC bound E 1 S as efficiently as CH. We conclude that AC was the most effective adsorbent agent for binding E 1 , E 1 S, androstenone and skatole in vitro, followed by CH, Tween, PVPP and lastly BNT. These adsorbent agents may be useful for binding boar taint compounds in in vivo studies to decrease the risk of boar taint.

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Michaelis-menten absorption kinetics in drugs: ? Examples and implications

Cited by 22 publications

References 26 publications

Steady-state level and turnover rate of the tripeptide Tyr-Gly-Gly as indexes of striatal enkephalin release in vivo and their reduction during pentobarbital anesthesia.

Steady-state level and turnover rate of the tripeptide Tyr-Gly-Gly as indexes of striatal enkephalin release in vivo and their reduction during pentobarbital anesthesia.

Pharmacokinetics of the thiazide diuretics

In vitro assessment of the effectiveness of non-nutritive sorbent materials as binding agents for boar taint compounds

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