ENZYMIC HISTOCHEMISTRY OF GRANULAR COMPONENTS IN DIGESTIVE GLAND CELLS OF THE ROMAN SNAIL, HELIX POMATIA

Abstract

1. Cytochemical visualization methods for activity of acid phosphatase, β-glucuronidase, aminopeptidase and non-specific and E-600-resistant esterases were applied to digestive gland tissue from starved and feeding Helix pomatia. Other cytochemical methods used included Baker's acid hematein for phospholipid and the periodic acid Schiff method. 2. Calcareous cells stained only for acid phosphatase activity, by both lead-salt and an azo dye method. Calcium granules within these cells did not stain with the azo dye method while false-positive reactions in the granules were always obtained with the lead-salt method. Some increase in enzymic activity was detected in the cytoplasm of feeding animals. Secretory-resorption (SR) cells showed little activity for acid phosphatase. 3. The yellow granules in SR cells stained for β-glucuronidase activity in both starved and feeding animals. After feeding, SR cells showed an increase in enzymic activity, both in granules and more diffusely in the cytoplasm. Although some aminopeptidase activity was present, insignificant differences in location and intensity of the enzyme were detected. 4. SR cells stained intensely for non-specific esterase activity. Cytoplasmic staining for this class of enzymes was intense in feeding animals. Treatment with the inhibitor E-600 resulted in loss of cytoplasmic staining; activity persisted in yellow granules in both starved and feeding animals. Some activity was detected in small, colorless granules. 5. Phospholipid was detected in peripheral regions of the SR cells from starved and feeding animals. The reaction was diffuse in starved animals but concentrated at the luminal border of the SR cells in fed animals. Yellow granules of SR cells were periodic acid Schiff-positive. Especially in fed animals, periodic acid Schiff granules appeared at the luminal border of SR cells. Starved animals fed on lettuce leaves impregnated with horse-radish peroxidase showed accumulation of enzyme in vacuoles closely associated with the yellow granules. 6. The observations extend the concepts, advanced by earlier workers, that granular components of the secretory-resorption cells play a significant role in digestion in the snail. The location of activity of the several hydrolases studied, and the alterations in response to feeding, suggest that these classes of enzymes and the granules form a functioning unit in the physiology of intracellular digestion in Helix.