The enzymes of the pyloric caeca of Pisaster ochraceus Brandt : an histochemical study.
Date
1973
Authors
Thompson, Kathleen Anne Woolley
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
1. An histochemical study of the enzymes of the pyloric caeca of the starfish Pisaster ochraceus was carried out using frozen tissue sections. The enzymes were demonstrated with simultaneous capture (coupling) reactions using azo dye methods. The effects of nutritional state on enzyme patterns were investigated in starfish which had been deprived of food for up to 10 weeks, or allowed to feed normally.
2. An histological investigation was concomitantly carried out on tissue samples from the same animals utilizing paraffin sections. The cellular details were observed during the various nutritional conditions outlined above.
3. The four enzymes tested for (acid phosphatase, alkaline phosphatase, leucine aminopeptidase, and esterase) were all demonstrated within the digestive epithelium. The enzymes appear to be affected more by the nutritional state of the asteroid than by the season.
4. Season of the year has little effect on the cellular inclusions of the caecal tissue, but the nutritional condition of the starfish does have a marked effect.
5. During starvation the zymogen granules are few, and the zymogen vacuoles are small and scarce. However, these inclusions never disappear entirely and are present after 10 weeks of starvation. Immediately after feeding, however, the zymogen granules increase markedly in number and the associated vacuoles increase in size as well as number.
6. The lipid deposits are not diminished significantly by starvation. Following feeding the lipid deposits and storage granules become very abundant within the tissue.
7. The possible activities of the enzymes are considered in relation to the functions of the pyloric caeca. The phosphatases, especially alkaline phosphatase, seem to perform an important role in nutrient transport. Acid phosphatase and, perhaps to some extent, leucine aminopeptidase may be important in intracellular (lysosomal) digestion, especially in starved animals. Leucine aminopeptidase also functions in extracellular digestion, whereas the esterases probably function primarily in the hydrolysis of the storage products of the pyloric caeca as well as in lipid absorption and metabolism.
8. The isozyme concept is discussed in relation to its bearing upon enzyme localization and function. The localization and level of activity of the enzymes (in particular, alkaline phosphatase) are seen to be influenced by their function(s). Different localization sites possibly indicate different isozymes and reflect different metabolic needs at those sites.