INTRACELLULAR DIGESTION AND HYDROLYTIC ENZYMES IN THE PHAGOCYTES OF PLANARIANS

¹ Department of Pathology, Albert Einstein College of Medicine, New York 61, N. Y.

1. The presence of the three hydrolytic enzymes, acid phosphatase, aminopeptidase and -glucuronidase have been demonstrated in relation to digestion phenomena in Dugesia dorotocephala and D. tigrina.

2. None of these enzymes were detected in the gastrodermis of starved animals. Acid phosphatase activity appears 5 minutes after feeding commences and is closely identified with formation of the food vacuoles. Maximum phosphatase activity is present in all vacuoles 24 to 48 hours after feeding; a slight reaction occurs in the cytoplasm of all gastrodermal cells at this time. Three days after feeding, acid phosphatase activity declines until one week after feeding, no activity is evident.

3. Aminopeptidase activity is present in the mesenchyme of starved animals where it is probably associated with "self-digestion" phenomena related to the nutritional state of the animal. In general, aminopeptidase activity parallels that of acid phosphatase. While intracellular localization of -glucuronidase was not achieved, its activity in the digestive tract was observed to be similar to that of the other two enzymes studied.

4. The results obtained on a histochemical level are discussed in terms of current concepts of the mechanism of intracellular digestion.