1. In continuation of work already reported (Menzies, 1949) further data are presented on the structure and cyto-chemistry of the granules in the oxyntic cells of the rat's stomach.
2. After multiple doses of pilocarpine or histamine, and after feeding, the phospholipine (as shown by acid haematein) is shed from some or all of the granules. The lipine first leaves the granules in cells situated in the basal part of the tubules, and finally those in the neck of the tubules, but a non-lipine lipoid remains in all the granules (as shown by sudan black).
3. The granules enlarge after prolonged starvation as they do after a single injection of pilocarpine; but after extraction of lipoids by hot pyridine and subsequent straining with iron haematoxylin, enlargement (i.e. of the non-lipoid moiety) is shown only after prolonged starvation.
4. A light, uncoloured central area is found in some of the largest granules after feeding and colouring with acid haematein.
5. An acid phosphatase appears in the oxyntic cells whose granules are about to lose their lipine component, and it disappears when they have done so. It is suggested that the acid phosphatase may cause hydrolysis of the phospholipine.
6. Only after prolonged starvation is there any apparent change in granule numbers, when they are decreased.
Insulin activates p21Ras and guanine nucleotide releasing factor in cells expressing wild type and mutant insulin receptors.
