McLeay, Lance M.Jury, Denis R.2025-08-072025-08-071978https://hdl.handle.net/10289/17555Using a modification of the extraction procedure of Gregory and Tracy (1964), and a perfused rat stomach bioassay, gastrin-like activity has been located in the ovine rumen, reticulum, omasum, abomasal body, antrum, duodenum and caecum. The antrum showed the highest concentration of gastrin-like activity, but substantial concentrations were found in the rumen, reticulum, omasum and caecum and proximal duodenum declining progressively with distance from the pylorus. A lesser concentration occurred in the abomasal body. Consideration of the relative total content of gastrin-like activity showed that the amount of extra-antral activity was substantial. The active principle was unlikely to have been cholecystokinin as the extracts had isoelectric points of a more acidic nature than that of cholecystokinin. Similarly, bioassay using an isolated guinea-pig ileum showed histamine to be absent from the extracts. Extraction of rumenal, reticular, omasal, abomasal body and antral mucosa and muscle separately showed that the gastrin-like activity resided almost completely in the mucosa. An investigation of the gastrin-like activity of air dried and freeze dried extracts showed that the freeze dried extracts were approximately 50% more active than the air dried extracts. Bioassay of a freeze dried antral extract over a twenty four week period showed that the activity was maintained for the initial six weeks, and that 80% of the activity was then lost over the following eighteen weeks. Studies using columns of Sephadex have shown that extracts from all regions of the ovine gastro-intestinal tract investigated were similar and consisted of several components of differing molecular weight. By a comparison of their respective molecular weights, to those reported for components separated from extracts of non-ruminant origin, it seems likely that components corresponding to MG, HLG, BG, BBG and component I were present in varying amounts. The response to infusions of gastrin extract in fed and fasted sheep were different. In fasted sheep infusions of extract, after a relatively long latent period, caused a small, but prolonged increase in acid secretion. In contrast pentagastrin caused an immediate and pronounced response. In fed sheep the responses were variable. Experiments on a single dolphin (Delphinus delpis) have shown there to be gastrin-like activity present in the forestomach, mainstomach, pyloric stomach, duodenal ampulla and intestine of this mammal. The distribution of gastrin-like activity reported in the present work has been compared to previous reports concerning the distribution of gastrin activity in animals with a more simple stomach, and the possible function of gastrin in the ruminant has been discussed.enAll items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.Thesis