By use of an in vivo canine chambered stomach preparation in which the gastric mucosa was partitioned into two equal halves, the effect of topical 16,16-dimethyl PGE2 (DMPGE2) (1 microgram/ml of perfusate) and 8% and 40% ethanol on tissue levels of nonprotein sulfhydryl compounds was assessed. Both DMPGE2 and 8% ethanol significantly increased (P less than 0.005) mucosal levels of nonprotein sulfhydryls when compared with corresponding mucosa bathed with saline alone. In contrast, mucosa bathed with 40% ethanol showed significantly decreased levels. If mucosa was bathed with DMPGE2 or 8% ethanol prior to exposing the stomach to 40% ethanol, this depletion in sulfhydryl compounds was not observed. Since other experimental observations have shown that exogenously administered prostaglandins and mild irritants (such as low-dose alcohol) can prevent gastric mucosal damage by necrotizing agents (such as high-dose alcohol), our findings are consistent with the hypothesis that nonprotein sulfhydryls may play a role in mediating gastric mucosal protection.

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SUMMARY1. An isolated gastric mucosal preparation from the dog stomach which is capable of acid secretion is described. Average values for normal resting potential difference (p.d.) was 49 + 2 mV (mucosal side negative with respect to the serosal side), shortcircuit current (I8c) was 172 + 4 ,uA and resistance (R) was 285 + 6 Q. cm2. Low rates of spontaneous acid secretion (0-0.58,uequiv/cm2.hr) were present initially but following short-circuiting of the tissue these values decreased to low levels (less than 0.1 uequiv/cm2. hr) within an hour.2. Histamine in doses exceeding 10-6 M stimulated acid secretion, increased Ih, and decreased R. Concentrations ranging from 10-5 to 8 x 10-4 M produced maximal secretion. The maximal secretary rate achieved was 4-24 + 0 35 ,uequiv/cm2. hr.3. Pentagastrin (10-8 M) and acetylcholine (10-6-10-5 M) also stimulated acid secretion with a lower maximal secretion as compared to histamine stimulation. These concentrations of pentagastrin and acetylcholine did not alter histamine stimulated acid secretion. Higher concentrations of pentagastrin (10-6 M) and acetylcholine (10-4 M) reversibly inhibited acid secretion of histamine stimulated mucosa.4. These results demonstrate that there are many similarities between in vitro and in vivo findings on the dog stomach, indicating the great potential of the in vitro dog gastric mucosa for studies on the mechanism of action and interaction of gastric secretagogues.

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