The release of histamine during gastric acid secretion in conscious rats.

1. Conscious gastric-cannulated rats were given [(3)H]histidine and aminoguanidine by dosage procedures intended to build up fast-turnover and slow-turnover pools of tissue [(3)H]histamine. Acid secretion was stimulated by I.V. infusion of pentagastrin, and the [(3)H]histamine content of gastric juice and excretion in urine were determined at 30 min intervals.2. The amount of [(3)H]histamine in gastric juice derived from either a slow-turnover or fast-turnover pool was very low in unstimulated animals, and was not altered during pentagastrin-stimulated acid secretion.3. From a slow-turnover pool pentagastrin caused increased urinary excretion of [(3)H]histamine. This was abolished by gastrectomy, so that the [(3)H]histamine liberated by pentagastrin from this pool appears to have been derived from the stomach. Evidence was not found for the existence of a slow-turnover histamine pool in the glandular mucosa of the stomach, and the source within the stomach of this pentagastrin-liberated histamine is thus uncertain.4. From a fast-turnover pool pentagastrin did not cause an increased urinary excretion of [(3)H]histamine. The amount of [(3)H]histamine excreted by gastrectomized rats was not different from that produced by gastric-cannulated animals. This suggests that a high proportion of urinary histamine derived from a fast-turnover pool was non-gastric in origin.5. Differences in the time scale of [(3)H]histamine release and acid secretion were not found. In some experiments the urinary output of [(3)H]histamine was prolonged beyond the end of pentagastrin administration and gastric acid secretion. However, the overall data do not suggest that urinary histamine output and gastric acid secretion take different time courses.