Alkaline secretion by frog gastric glands measured with pH microelectrodesin the gland lumen

1. In the present work we have measured the pH of the secreted fluid within the gland lumen of isolated but intact gastric mucosa of Rana esculenta. T issues were mounted in a double chamber allowing continuous perfusion of th e mucosal and serosal compartment, and the measurements were made with doub le-barrelled pH glass microelectrodes inserted into the glands from the ser osal surface under microscopic inspection. 2. During inhibition of H+ secretion by cimetidine (100 mu m) the luminal g land pH (pH(g1)) averaged 7.60 +/- 0.05 pH units (mean +/- S.E.M.; n = 35), a value significantly higher than bath solution pH (7.45 +/- 0.02; P< 0.00 1) and also higher than intracellular pH of oxyntopeptic cells (pH(1)), whi ch averaged 7.53 +/- 0.06 (n = 18). 3. Stimulation of acid secretion with histamine (500 mu M) reversibly decre ased pH(g1) to values which could be as low as 2.5. Together with electroph ysiological criteria this response was routinely used to verify the proper location of the microelectrode tip within the gland lumen. 4. Stimulation with carbachol (100 mu M) or pentagastrin (50 mu M) in the p resence of cimetidine rapidly and reversibly increased pH(g1) by 0.10 +/- 0 .01. pH units (n = 24; P < 0.001) and 0.09 +/- 0.02 pH units (n = 6; P < 0. 05), respectively. 5. The observation that gastric gland fluid is more alkaline than the bath solutions and that carbachol or pentagastrin further alkalinize it strongly suggests that oxyntopeptic cells participate in gastric alkaline secretion at least under cholinergic stimulation.