GASTRIN CONTENT AND ACTIVITY IN SOME RUMINANTS AND SOME EQUINES

Abstract

Attempts were made to extract gastrin from the cardiac, fundic pyloric, duedenal osecal and colonic mucosa of goats, sheep, cattle, male and female donkeys, using a modification of the gastrin extraction method introduced by Blair et al (1961). The large animals used i.e. cattle and donkeys, gave higher yields of crude pyloric gastrin per animal than the smaller animals like the goat and sheep. In the ruminants, cattle gave the highest pyloric extract yield per gram mucosa followed by goat and sheep was the least. In the equines used, male donkey gave more crude pyloric gastin extract than the female donkey. In both the ruminant and equines, the duedenal mucosas gave less extract yield than the corresponding pyloric mucosas. Crude extracts of the fundic, cardiac, caesium and colonic mucosa were obtained in the first two used animals of each specie and when none of them contained gastrin activity, further extraction from these areas was discontinued. The gastrin activity of the crude extracts was determined by bioassay technique using a modification of Ghosh and Schild (1958) method. Male anaesthetized rats with their stomachs perfused with normal saline were employed. Gastrin extracts were dissolved in saline and known concentrations were injected intravenously into the rats, and the solid secretory responses were recorded by titrating the gastric affluents collected every 10 minutes, using both manual and automatic titrations. Synthetic human gastrin I was used as the reference standard. A 2+ 2 assay method was used and the index of precision of the assays was 0.186 or less thus it was very suitable for quantitative work (Loraine & Bell, 1966). Gastrin activity was found in both the duodenal and pyloric extracts. There were no significant differences in the gastrin activity of the pyloric extracts from the three ruminant species, though goat contained highest activity and cattle the least. Gastrin activity of the donkeys pyloric extracts was significantly lower than in the ruminants. There was no differences in gastrin activity between the pyloric extracts of the male and female donkeys. The duodenal extracts generally showed less gastrin activity than the corresponding pyloric extracts. Duodenal extracts of donkeys were relatively more potent than in the ruminants. Inert protein content was found to be higher in the donkeys pyloric gastrins than in the ruminants and also all the duodenal gastrins contained higher inert protein values than the pyloric extracts, thus it was established that the gastrin activity of the extract was inversely related to the quantity of inert protein contained. The hindrance contents of the pyloric and dudenal extracts were determined and the values obtained ranged between 34-37.5ng/mg crude extract, which was found to be too small to cause the obtained solid secretory response in the rat preparations. Serotonin and Acetylcholine were also proved to be absent or if present, the quantities were too small to affect the solid secretory response of the gastrin extracts. Partial purification of the crude extracts was done using the Sephadex gel-column. Similarity in the molecular sizes of the aqueous fractions of the macro-molecules to which the used crude pyloric gastrins could be attached and also similarity in the sizes of both the pyloric and duodenal gastrins were established. The kidneys of rats were shown to be important sites in gastrin metabolism. A 40 percent increase in acid secretory response was obtained when injected gastrins were not allowed to get into the kidneys.