Pepsin secretion in anaesthetized cats stimulated by pentagastrin and gastrin II in the presence or absence of secretin.

1. In fasting anaesthetized cats pentagastrin and gastrin II, infused alone in doses which evoked a large acid response, did not stimulate the secretion of pepsin. However, peptic secretion increased significantly when either acid stimulant was infused simultaneously with a dose od Boots' secretin, in itself below the threshold for peptic stimulation. 2. The potentiation by pentagastrin and gastrin II of the peptic response to secretin was similar to the potentiation observed when caerulein, histamine and N-methyl histamine are given with secretin, an effect we have attributed to a non-specific increase of gastric mucosal blood flow which accompanies the infusion of these acid stimulants and effectively increases the concentration of secretin delivered at the site of the chief cell in the gastric mucous membrane.