Pharmacokinetics of 5-aminolevulinic-acid-induced porphyrins in tumour-bearing mice.

Photodynamic therapy and photodynamic diagnosis help to support efficient treatment of superficial and early-stage cancer. During the last few years, 5-aminolevulinic acid (5-ALA), a precursor of haemoglobin in the haem biosynthetic pathway, was used to stimulate endogenous porphyrin production. In the following the time dependence of 5-ALA-induced porphyrin concentration will be investigated on several tissues in an in-vivo tumour model. 5-ALA was administered intravenously at a concentration of 50 mg-1 body weight. According to a certain time schedule the animals were sacrificed and 12 different organs as well as the tumour were removed. During excitation with the violet light of a Kr+ laser, porphyrin fluorescence spectra in the range 550-750 nm could be detected on the tissue samples. The intensity of the emission spectra at lambda = 635 +/- 2 nm was taken as a measure of the porphyrin concentration. All tissues showed porphyrin fluorescence. Brightest fluorescence was found on the tumour. A maximum contrast of the fluorescence intensity between the tumour and the non-malignant organs of up to 30 was observed at 4-6 h post-injection. The kinetics of the porphyrin concentration depend on the organ. Simple mathematical models will be derived and discussed.

The effect of irradiated volume on the chronic radiation damage of the rat large bowel.

PURPOSE: The dependence of the structural and the functional chronic radiation damage in the large bowel of rats was investigated in order to develop criteria for optimising treatment plans. MATERIAL AND METHODS: Rats were locally irradiated to different volumes of their rectum. The resulting chronic damage was determined by clinical observation, by rectoscopy and by histopathology. RESULTS: The structural damage as well as the functional damage depend very much on the dose distribution in the large bowel, however, this influence is different for structural and for functional damage expression. Much less field size effect was seen for the structural damage of ulceration than for the functional damage of rectal obstruction when the length of whole circumference irradiation was reduced or when only half of the circumference was irradiated. CONCLUSIONS: Different criteria are likely to apply for different types of damage even in one particular organ. The volume or the proportion of an organ which receives the target dose is not always a useful criterium for optimizing treatment plans.

Penetration potency of topical applied delta-aminolevulinic acid for photodynamic therapy of basal cell carcinoma.

Penetration potency of delta-aminolevulinic acid (ALA) was studied by examining fluorescence of endogenous protoporphyrin IX in different histological types of basal cell carcinoma. Ten basal cell carcinomas were coated with an ointment containing 10% ALA prior to excision; five served as controls. Tumors were excised either 4 h or 12 h after application of ALA using a modified Mohs' micrographic surgical technique. Horizontal sections were cut from deep dermis to tumor surface and examined under a fluorescence microscope. After 4 h of application, only skin appendages demonstrated fluorescence typical of protoporphyrin IX. After 12 h, fluorescence was detectable in tumor cells in deep dermis. The five controls revealed no fluorescence at any site. These results may confirm the high penetration potential of topically applied ALA and its usefulness in photodynamic therapy. For tumors penetrating to deep dermis, an application time of more than 4 h seems necessary, at least when hydrophilic solvents for ALA are used.

The effect of dose fractionation on radiation injury in the rat stomach.

Localized 300 kV X-irradiation of the rat stomach with single and fractionated (two and five fractions given daily and in 4 weeks) doses was performed. In the second and third week after irradiation acute radiation gastritis developed which resulted in a dose-dependent drop in body weight. The alpha/beta value for a 10% drop in body weight was calculated to be 9.6 Gy (95% confidence interval 2.1-25.9 Gy). Between 4 and 40 weeks after irradiation subchronic radiation damage was observed which presented itself as atonic dilatation of the stomach. For this effect, the alpha/beta value is 4.8 Gy (graphical estimation) and 5.3 Gy (95% confidence interval 0.4-13.1 Gy; direct Poisson model). In the five-fraction (5F) experiment a significant increase in tolerance amounting to 0.8 Gy/day for the acute effect and 0.4 Gy/day for the subchronic effect was observed when intervals were increased from 1 day to 1 week. In a separate experiment animals were pre-irradiated with subtoxic and toxic radiation doses. One hundred days later acute tolerance to a second irradiation was completely restored. However, no recovery of subchronic damage was observed.

[Development of methods for measuring the emptying time of solid and liquid test meals in rat stomachs]. / Entwicklung von Methoden zur Messung der Entleerung fester und flüssiger Testmahlzeiten aus dem Rattenmagen.

Different methods for experimental measuring the gastric emptying time in the rat have been developed. For the invasive method of measuring the stomach emptying time of a solid test meal containing Amberlite pellets too many animals are necessary. On the other hand, for the non-invasive examination of the emptying of a radioactively marked liquid test meal by scintigraphy the resolution of the gamma-camera is too low. However we were able to develop a non-invasive fluoroscopic method for the simultaneous measurement of the gastric emptying of a solid (10 radiodense markers) and a liquid (0.5 ml diluted contrast medium) test meal. Using this method it was possible to examine the influence of stomach motility stimulating drugs, such as the parasympathomimeticum carbachol and the dopamine antagonist metoclopramide.

[Acute and chronic disorders in gastric emptying after the x-ray irradiation of the rat stomach and their therapeutic modification]. / Akute und chronische Störungen in der Magenentleerung nach Röntgenbestrahlung des Rattenmagens und deren therapeutische Beeinflussbarkeit.

After localized 300 kV X-irradiation of the rat stomach the stomach emptying time of a liquid and a solid test meal was examined with a non-invasive radiological method. In the acute period one to three weeks after irradiation with single doses between 10.7 and 21.3 Gy we observed a faster emptying of the liquid and a delayed emptying of the solid test meal. The faster emptying of the liquid test meal was treated successfully with atropine. In the chronic period we observed a delayed emptying of the liquid and of the solid test meal. These emptying disorders were treated partially successfully with the parasympathomimeticum carbachol and they were treated completely successfully with the dopamine antagonist metoclopramide.

[Effects of tetrachlorodecaoxide (TCDO) in chronic radiation lesions of the rat colon]. / Die Wirkung von Tetrachlordecaoxid (TCDO) auf den chronischen Strahlen-schaden am Rattenkolon.

The influence of tetrachlorodecaoxide (TCDO) on the chronic radiation damage after local irradiation of the rat colon was examined when given at different times and at different doses. A tetrachlorodecaoxide treatment before the acute period resulted in an extension of the latency period. When tetrachlorodecaoxide was given by the highest dose of 0.8 ml WF 10 at the onset of the chronic phase we observed an increase in the survival rate. Endoscopically and histologically we did find demonstrable signs of an improved healing of the mucosa.

Effect of X-irradiation on the stomach of the rat.

A model for localized 300 kV X-irradiation of the rat stomach was developed. After irradiation with single doses, three distinct gastric disorders were observed which occurred at different latency times. Acute death 2-3 weeks after irradiation was caused by an erosive and ulcerative gastritis and occurred in all animals given 28.5 Gy without diet, in 17% of the animals given 28.5 Gy plus diet, and in 13% of the animals given 23 Gy. Subacute to chronic fatal disorders 4 weeks to 7 months after irradiation were seen as stomach dilatation and gastroparesis, associated with the replacement of the normal gastric mucosa by a hyperkeratinized multilayered squamous epithelium. These disorders occurred in 40-100% of the animals after doses between 16 Gy and 28.5 Gy (+diet). An ED 50 value of 19.2 Gy (16.5-21.2 Gy, 95% confidence interval) was calculated for this gastroparesis. Late gastric obstruction exceeding 7 months after irradiation was seen in the rats because of profound changes in the gastric wall in 13-18% of the animals after doses between 23 Gy and 14 Gy. In animals surviving these three periods, an atrophic mucosa and intestinal metaplasia developed. From functional and morphohistological studies, it can be concluded that there are differences in the pathogenesis of the fatal radiation damage for each of these periods after irradiation.

[Endoscopic control of the course and its histological correlation in chronic radiation injury of the rat rectum]. / Die endoskopische Verlaufskontrolle und deren histologische Korrelation des chronischen Strahlenschadens am Enddarm der Ratte.

On the basis of endoscopic investigations, the reaction to X-radiation of the hindgut of the rat could be divided into four phases. Their courses after different radiation doses as well as after dietary influence are described. This enabled us-besides the acute (diarrhoea) and chronic (diarrhoea followed by intestinal occlusion) phases shown by clinical examination - to demonstrate the early vascular reaction (first week after irradiation) as well as the asymptomatic interval between the acute and chronic phases. The interval phase was found to be of importance for prognosis and therapy, because all animals who died later on of intestinal occlusion developed already during this phase circular ulcerations which could be demonstrated by endoscopy.