Mucosal blood flow changes in the human stomach measured by the 99mTc-4-methylaminophenazone clearance technique

The effect of gastric secretory inhibitors, vasoactive agents and gastrointestinal peptide hormones were investigated on gastric mucosal blood flow (MBF) and HCl secretion in 197 subjects. Changes in MBF were estimated by a new clearance substance, 99mTc-4-methyl-aminophenazone originally described by the authors. The procedure seemed to be suitable for characterizing changes in MBF without any toxic side effect or considerable radioactive loading of the patient or its surroundings. The studies were performed after a secretory steady state had been achieved by continuous pentagastrin infusion. Some experiments were done in the fasting stomach instilled with 0.160 N HCl. Secretory inhibition following atropine, pirenzepine, ranitidine and somatostatin was a primary effect of these substances, the observed MBF decrease being a secondary one. In contrast, vasopressin caused a fall in mucosal blood supply through vasoconstriction, the concomitant secretory inhibition being a secondary phenomenon. Certain doses of dopamine and terbutaline increased MBF without influencing HCl secretion. Glucagon in the dose used did not influence either mucosal blood flow or acid secretion. Synthetic secretin in the fasting stomach increased MBF without affecting HCl production; during pentagastrin stimulation it inhibited acid production while MBF remained unchanged. Cholecystokinin-octapeptide proved to be a direct vasodilating agent with a slight acid output increasing effect. Divergent effects of some drugs on mucosal blood flow and HCl production may be important in the pathology of hypoxic ulcerative damage and in the reparative processes of gastric ulceration. The 99mTc-4-methyl-aminophenazone clearance technique proved to be a reliable method for screening of drugs possessing vasoactive or secretion influencing properties.