SU-MMARY 1. The gastric mucosal blood flow has been measured by the amidopyrine clearance technique in anaesthetized cats. The total gastric blood flow has been (a) measured directly and (b) calculated by the Fick principle from the amidopyrine concentrations in gastric arterial and venous blood and the gastric output of amidopyrine.2. Observations on the recovery of added amidopyrine from arterial and venous blood and plasma, and on the rate of transfer of amidopyrine from corpuscles to plasma, support the underlying assumptions of the amidopyrine method of measuring mucosal blood flow.3. If acid solutions are instilled into the stomach the mucosal blood flow of the non-secreting stomach may be measured by the amidopyrine technique.4. Total gastric and mucosal blood flow increased linearly with increase in H+ secretion, stimulated by histamine or gastrin. The increase in total flow was entirely due to the increase in mucosal flow.5. The relationship between mucosal blood flow and H+ secretion was the same for histamine and gastrin responses, and was unaffected by maintaining the total flow at a constant level, or by reduction of the circulating blood volume. Increase in blood volume altered the relationship so that there was a greater increment in mucosal blood flow for any increase in H+ secretion.6. It is concluded that valid observations may be made on secretion and blood flow relationships in acute anaesthetized preparations.

SUMMARY1. Pancreotone is a polypeptide material obtained from ileal and colonic mucosa by extraction with alcohol and subsequent precipitation by bile salts.2. In anaesthetized cats it inhibits the actions of secretin on the pancreas, and of pancreozymin on the pancreas and gall-bladder.3. Pancreotone has a less powerful inhibitory action on pentagastrin-stimulated gastric secretion.4. The actions of pancreotone resemble the inhibitory effects on the pancreas and stomach of intraileal and intracolonic infusions of oleic acid and other substances in cats with the vagal and splanchnic nerves cut. Pancreotone may be the humoral mediator of these inhibitory effects.5. A possible relationship between the actions of pancreotone and somatostatin on the stomach, and of pancreotone and pancreatic polypeptide on the pancreas, is discussed.

SUMMARY1. Gastric mucosal blood flow (MBF) and gastric acid secretion have been compared and related during the infusion of a wide dose range of gastrin extracts, pentapeptide (Peptavlon, I.C.I. 50123) and histamine.2. Constancy of increase in mucosal blood flow relative to H+ secretion was obtained with gastrin stimulation, whereas histamine stimulation produced higher ratios of mucosal blood flow to H+ secretion, and these ratios declined as each experiment continued.3. The importance of considering only the increase in mucosal blood flow in relation to acid secreted is demonstrated.4. It is concluded that the differences shown in the AMBF/AH+ with histamine and gastrin stimulation provide further evidence that the amidopyrine clearance technique measures gastric mucosal blood flow.

SUMMARY1. Gastric acid and mucosal blood flow responses to sustained gastrin stimulation were studied in anaesthetized cats.2. Acid and mucosal blood flow showed identical rates of tachyphylaxis to both large (maximal) and small doses of gastrin.3. Isopropylnoradrenaline infused either intravenously or close arterially to the stomach produced increases in blood flow unrelated to time following the peak response to large doses of gastrin, whereas increases in acid secretion appeared to be a part removal of the acid tachyphylaxis.4. During stimulation by small doses of gastrin, isopropylnoradrenaline increased both blood flow and acid secretion above the peak responses to gastrin alone.5. Increases in gastrin stimulated acid and mucosal blood flow were also produced by expansion of the blood volume by dextran-saline infusions.6. The physiological significance of these findings is discussed. 7. It is concluded that tachyphylaxis of gastric acid secretion to gastrin may be a function of the primary tachyphylaxis of mucosal blood flow.

SUMMARY1. Somatostatin, 10 jug kg-1 hr-1, inhibited gastric acid and pepsin secretion stimulated by pentagastrin, 8 ,g kg-1 hr-1, in conscious and anaesthetized cats with chronically implanted gastric fistulae. In the acutely surgically prepared anaesthetized cat, Somatostatin inhibited pepsin secretion but produced little inhibition of gastric acid secretion or mucosal blood flow.2. Secretin stimulated pancreatic juice volume was not significantly reduced in acutely prepared anaesthetized cats, but there was a limited reduction of cholecystokinin-pancreozymin stimulated pancreatic amylase secretion and gall bladder contraction.3. Somatostatin had neither stimulatory nor inhibitory effects on electrolyte and amylase secretion in the isolated saline-perfused cat pancreas.4. The results suggest that some of the effects of Somatostatin may depend on the interaction on the target cell of other factors, nervous or humoral which may vary in different experimental preparations.t Present address: