RESUMEN
OBJECTIVE: To investigate red fluorescence found in the digestive tract of Wistar rats submitted to stress produced by a liquid diet of 5% glucose and maintenance in darkness. BACKGROUND DATA: Protoporphyrin IX (PpIX) is produced by the Harderian gland, located in the inner corner of the eyes of rats. Under stressful conditions this gland increases the production of PpIX, which can be detected in different regions of the body, in a manner reminiscent of a porphyria. MATERIAL AND METHODS: Sixty-five Wistar rats were used in this study. The fluorescence spectra were registered with optical resolution better than 1.7 nm. The rats were fed a 5% glucose diet, exclusively, up to 120 h. The animals were evaluated throughout the diet period, which included two sequential experiments: considering the red fluorescence of their intestinal tract and the fluorescence that appeared in some external parts of their bodies (paw, tail, nose, and scrotum). The normal diet was reintroduced and new spectra were obtained after 24 and 48 h. RESULTS: Experiment I showed a marked, time-dependent increase in the intestinal content of porphyrin in rats fed the glucose diet. The fluorescence spectrum of the material identified it as PpIX. The spectra collected in Experiment II showed an increase in fluorescence in the four external areas associated with the duration of the diet. This fluorescence disappeared after reintroduction of the regular diet. CONCLUSION: The feeding of a restricted diet (5% glucose) to Wistar rats resulted in reversible porphyria. Measurement of the fluorescence intensity may be a reliable method for monitoring the porphyrin content of tissues.