Groth L
Leo Pharmaceutical Products, Department of Dermatological Research, Ballerup, Denmark.
Acta Derm Venereol Suppl (Stockh). 1996;197:1-61.
This thesis describes the methodology and validation of cutaneous microdialysis for the study of skin penetration of various topically applied substances in experimental dermatological research. Microdialysis is a sampling technique which makes it possible to measure substances in the extracellular water space in human and animal skin in vivo. A microdialysis probe, i.e. a tubular semipermeable membrane connected to afferent and efferent tubings, is placed in the dermis and perfused. Substances from extracellular space may diffuse through the pores of the membrane and be collected in the dialysate for further analysis. Glucose, sodium fusidate, betamethasone 17,21-dipropionate and calcipotriol were chosen as model substances and were investigated by in vitro microdialysis. The perfusion rate, the length of the membrane, stirring rate and temperature influenced recovery of the substances. Lipophilic compounds tend to have low recoveries and differ in recovery and loss. Insertion of the microdialysis probe causes a trauma in the skin. Rat and human skin were studied in vivo. Increase in skin blood flow, erythema and skin thickness were demonstrated by laser Doppler perfusion imaging, Dermaspectrometer colorimetry, Minolta Chromameter colorimetry and ultrasound imaging of cross-sectional skin structure. In addition histamine was released in rat skin due to the needle insertion. An equilibration period of minimum 90 min in human skin and 30 min in rat skin after the insertion is necessary to allow the effects of trauma to diminish. To obtain measurable concentrations in the dialysate in rats treated topically with the lipophilic drug betamethasone 17-valerate, unrealistic high doses and penetration enhancement were required. The highly protein-bound drug fusidic acid was not measurable in the dialysate after topical application, probably due to very low concentrations of free diffusible drug. Measurable concentrations were only observed after high doses of oral administrations of fusidic acid. Calcipotriol could not be detected in the dialysate. The microdialysis technique is probably primarily useful for the study of hydrophilic substances and substances with low protein binding and low molecular weight. However, application of cutaneous microdialysis for the study of lipophilic substances need further methodologically development.
本论文描述了在实验性皮肤病学研究中，用于研究各种局部应用物质经皮渗透的皮肤微透析方法及其验证。微透析是一种采样技术，它能够在体内测量人和动物皮肤细胞外水空间中的物质。将一个微透析探头，即连接有传入和传出管道的管状半透膜，置于真皮中并进行灌注。细胞外空间中的物质可通过膜的孔隙扩散，并收集在透析液中进行进一步分析。选择葡萄糖、夫西地酸钠、倍他米松17,21 - 二丙酸酯和骨化三醇作为模型物质，并通过体外微透析进行研究。灌注速率、膜的长度、搅拌速率和温度会影响物质的回收率。亲脂性化合物往往回收率较低，且在回收率和损失方面存在差异。微透析探头的插入会对皮肤造成创伤。对大鼠和人类皮肤进行了体内研究。通过激光多普勒灌注成像、皮肤光谱仪比色法、美能达色差仪比色法以及皮肤横截面结构的超声成像，证实了皮肤血流量增加、红斑和皮肤厚度增加。此外，由于针刺插入，大鼠皮肤中释放了组胺。插入后，人体皮肤至少需要平衡90分钟，大鼠皮肤至少需要平衡30分钟，以使创伤的影响减弱。为了在局部用亲脂性药物倍他米松17 - 戊酸酯治疗的大鼠透析液中获得可测量的浓度，需要使用不切实际的高剂量药物并增强渗透。局部应用后，透析液中无法检测到与蛋白质高度结合的药物夫西地酸，这可能是由于游离可扩散药物的浓度非常低。仅在高剂量口服夫西地酸后才观察到可测量的浓度。透析液中未检测到骨化三醇。微透析技术可能主要适用于研究亲水性物质以及蛋白质结合率低和分子量低的物质。然而，将皮肤微透析应用于亲脂性物质的研究还需要进一步的方法学开发。
