Membrane-bound ATP-dependent energy systems and the development of the gastric mucosal damage in rats produced by 0.2 M NaOH, 25% NaCl, 0.6 M HCI and 96% ethanol.

Damage to the gastric fundic mucosa was produced in rats by intragastric administration of 1 ml 0.2 M NaOH, 25% NaCl, 0.6 M HCl or 96% ethanol; a control group received 1 ml saline solution. The animals were killed 1 h later, and the number and severity of ulcers (lesions) noted. The gastric fundic mucosa were excised and frozen, and assayed enzymatically for adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP) and lactate, while the tissue level of cyclic adenosine monophosphate (cAMP) was estimated by radioimmunoassay. It was found that: (i) the number and severity of gastric lesions (ulcers) increased significantly in all the groups treated by the 4 necrotizing agents, (ii) the extent of ATP breakdown into ADP increased significantly, while the ATP transformation into cAMP by adenylate cyclase, and of cAMP into AMP by phosphodiesterase, decreased, (iii) the tissue level of lactate increased only in the 0.6 M HCl groups. It was concluded that: (i) the mucosal damage develops in consequence of a very active metabolic adaptation of the rat gastric fundic mucosa, notably the significantly increased ATP transformation into ADP, which is not the consequence of hypoxaemia, (ii) the feed-back mechanism system between the membrane-bound ATP-dependent energy systems is broken as the mucosal damage develops, the main changes being a significantly increased ATP transformation into ADP, a significantly decreased ATP transformation into cAMP, and significant alterations by neural, hormonal and pharmacological influences in the membrane-bound ATP-dependent energy systems.