title: Delta-aminolevulinic acid in superficial basal cell carcinomas and normal skin-a microdialysis and perfusion study.
abstract: Delta-aminolevulinic acid (ALA) is used for photodynamic therapy of basal cell carcinoma (BCC) as it is converted to protoporphyrin IX in tumour tissue. During illumination with 635 nm light a photochemical reaction takes place, singlet oxygen is generated and the tumour destroyed. In this study we used the microdialysis technique to quantify the concentration of ALA at a certain depth in tumour and healthy skin. The penetration ability of ALA was investigated as a function of time in BCCs (n = 14) and in normal skin (n = 4) after topical application. The microdialysis catheters were inserted intracutaneously and the depth position recorded by means of ultrasound. Microdialysate sample concentrations of amino acids and ALA were determined by high performance ion-exchange chromatography. A laser Doppler perfusion imager measured perfusion in the BCCs. The data show that the average depth of the microdialysis catheters was 0.5 mm. The interstitial ALA concentration in the BCCs increased from 0 to 3.1 mmol/L 15 min after application of ALA, whereas no measurable amounts of ALA were found in healthy skin. The blood perfusion was 2.5-fold increased in the BCCs. The interstitial levels of amino acids were not significantly changed during the ALA treatment. In summary, we found that ALA rapidly penetrates tumour skin. We conclude that microdialysis seems to be well suited for pharmacodynamic studies of ALA in skin.
authors.affiliation: Departments of Dermatology, Internal Medicine, Laboratory Medicine and Clinical Neurophysiology, Sahlgrenska University Hospital, Göteborg, Sweden. ann-marie.wennberg@sahlgrenska.se
authors.forename: A M
authors.initials: AM
authors.lastname: Wennberg
authors.forename: O
authors.initials: O
authors.lastname: Larkö
authors.forename: P
authors.initials: P
authors.lastname: Lönnroth
authors.forename: G
authors.initials: G
authors.lastname: Larson
authors.forename: A L
authors.initials: AL
authors.lastname: Krogstad
mesh_terms: D000368:Aged; D000622:Aminolevulinic Acid / Q000493:pharmacokinetics* / Q000627:therapeutic use; D002280:Basal Cell Carcinoma / Q000098:blood supply / Q000188:drug therapy* / Q000378:metabolism; D002852:Chromatography, Ion Exchange; D005260:Female; D006801:Humans; D008297:Male; D017551:Microdialysis; D008875:Middle Aged; D010477:Perfusion; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000493:pharmacokinetics* / Q000627:therapeutic use; D012867:Skin / Q000378:metabolism; D012878:Skin Neoplasms / Q000098:blood supply / Q000188:drug therapy* / Q000378:metabolism; D013997:Time Factors
chemical_list: D017319:Photosensitizing Agents; D000622:Aminolevulinic Acid