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L-dopa pharmacokinetics studied with microdialysis in patients with Parkinson's disease and a history of malignant melanoma
Linköping University, Department of Clinical and Experimental Medicine, Neurology . Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Geriatric . Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
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1999 (English)In: Acta neurologica Scandinavica, ISSN 0001-6314, Vol. 100, no 4, 231-237 p.Article in journal (Refereed) Published
Abstract [en]

OBJECTIVES: The pharmacokinetics of free L-dopa in blood and tissue of five parkinsonian patients with malignant melanoma was studied with microdialysis. In one case the effect of L-dopa treatment on 5-S-cysteinyldopa and the melanoma was studied. Gastric emptying and its effects on free L-dopa in blood were also investigated in one of the patients.

METHODS: Five patients were given 100 mg L-dopa with 25 mg benserazide. Blood and dialysates from the circulation and fatty tissue were collected for analysis. [13C]-Octanoic breath test was used for analyzing gastric half-emptying time.

RESULTS: Four of the patients had similar pharmacokinetic patterns for L-dopa and a significant (P < 0.05) increase of serum 5-S-cysteinyldopa occurring 30 min after L-dopa intake. Delayed L-dopa peaks and slow gastric half-emptying time were found in 1 patient. A dose-dependent increase of 5-S-cysteinyldopa occurred but no melanoma metastases were seen during long-term L-dopa therapy.

CONCLUSION: L-dopa therapy increases 5-S-cysteinyldopa levels but does not seem to cause progress of melanomas. Gastric emptying impacts L-dopa pharmacokinetics.

Place, publisher, year, edition, pages
1999. Vol. 100, no 4, 231-237 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-13529DOI: 10.1111/j.1600-0404.1999.tb00386.xOAI: oai:DiVA.org:liu-13529DiVA: diva2:20913
Available from: 1999-05-21 Created: 1999-05-21 Last updated: 2009-08-17
In thesis
1. Microdialysis as a Tool in Studies of L-Dopa and Metabolites in Malignant Melanoma and Parkinson’s Disease
Open this publication in new window or tab >>Microdialysis as a Tool in Studies of L-Dopa and Metabolites in Malignant Melanoma and Parkinson’s Disease
1999 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A model with human melanoma xenografts transplanted to athymic mice has been adopted for in vivo studies of 5-S-cysteinyldopa (an intermediate pigment metabolite), glutathione, and cysteine. L-Dopa is an intermediate metabolite in pigment formation and is also important in the treatment of Parkinson's disease, and therefore 1 have also studied the pharmacokinetics of this compound.

We were first to describe in vivo microdialysis in melanoma tissue and showed that dialysis membranes of cuprophane or polyamide are suitable for studies of interstitial 5-S-cysteinyldopa and selected thiols. Analytical procedures were also improved for quantitation of 5-S-cysteinyldopa, L-dopa, glutathione, cysteine, and N-acetylcysteine (NAC). In the melanoma xenografts the interstitial concentration of 5-S-cysteinyldopa reflected the high intracellular production of this intermediate metabolite. For in vivo manipulation of glutathione in the melanoma tissue we gave intraperitoneal injection of buthionine sulphoximine to the animals and thus reduced the glutathione concentrations substantially. We showed that restitution of glutathione in melanoma tissue occurs spontaneously and is not much improved by treatment with the cysteine deliverers NAC and L-2-oxothiazolidine-4-carboxylate (OTC). 5-S-Cysteinyldopa was not substantially affected by great variations in glutathione concentrations. Transport of NAC from intraperitoneal injection to melanoma tissue occurred rapidly and deacetylation to cysteine in vivo could be detected soon after NAC injection. In vivo formation of cysteine was slower from OTC than from NAC.

Pharmacokinetic studies of L-dopa in human subjects indicated a slight to moderate protein binding. Plasma free L-dopa had similar elimination T½ as interstitial L-dopa, but in some cases the elimination of total L-dopa was slower. Difficulties in intestinal absorption of L-dopa were revealed by microdialysis in blood and subcutaneous tissue. Studies showed that this was due to delayed emptying of the stomach. L-Dopa intake increased 5-S-cysteinyldopa concentrations in blood within 30 min in patients with Parkinson's disease and a history of melanoma. No melanoma activation occurred during long-term treatment with L-dopa.

Microdialysis is thus a safe and easily applied method for in vivo studies of both pigment metabolites from human melanoma tissue transplanted to nude mice and for pharmacokinetic studies of L-dopa.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 1999. 51 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 588
Keyword
Microdialysis, L-Dopa, Malignant Melanoma, Parkinson's Disease, in vivo
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-5009 (URN)91-7219-332-8 (ISBN)
Public defence
1999-04-09, Berzeliussalen, Hälsouniversitetet, Campus US, Linköpings universitet, Linköping, 13:00 (English)
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Note
On the day of the public defence the status of the articles IV, V and VI was: Submitted.Available from: 1999-05-21 Created: 1999-05-21 Last updated: 2012-01-24Bibliographically approved

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Dizdar (Segrell), NilGranerus, Ann-KathrineHannestad, UlfKullman, AnitaOlsson, Jan-EdvinKågedal, Bertil

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Dizdar (Segrell), NilGranerus, Ann-KathrineHannestad, UlfKullman, AnitaOlsson, Jan-EdvinKågedal, Bertil
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