PHOTOSENSITIZATION OF ALBINO-RATS FED ON LUCERNE-PROTEIN CONCENTRATE

1. The photosensitizing effect of leaf-protein concentrate (LPC) prepared from lucerne (Medicago sativa) was demonstrated when it was included in the diet of albino rats at concentrations between 40 and 480 g/kg diet. 2. Skin lesions of varying severity up to the sloughing of ears and tails occurred when such rats were illuminated with natural daylight through window-glass or with simulated daylight from a bank of lamps having emission maxima at 410, 437 and 660 nm and with approximately 4% of the energy of summer sunlight. 3. Protein concentrates prepared from ryegrass (Lolium multiforum) and a crude chlorophyll extract of spinach (Spinacea oleracea) did not cause these effects. 4. Extracts from blood plasma and livers of rats given lucerne LPC contained pheophorbide-a and two other unidentified green pigments, but no detectable phylloerythrin or chlorophyll. Extracts from the blood of rats given ryegrass LPC had no detectable pheophorbide or other chlorophyll-derived pigments. 5. The lucerne LPC given to the rats contained relatively large amounts of pheophorbide-a among a variety of pigments. The ryegrass LPC and the spinach extracts had only small amounts of this pigment relative to the other chlorophyll-type pigments. 6. These findings indicate that pheophorbide-a and related pigments are the agents responsible for the photosensitization of the rats. Possible explanations of their presence in lucerne LPC are discussed. © 1974, The Nutrition Society. All rights reserved.