RESTITUTION OF THE SURFACE EPITHELIUM OF THE INVITRO FROG GASTRIC-MUCOSA AFTER DAMAGE WITH HYPER-OSMOLAR SODIUM-CHLORIDE - MORPHOLOGIC AND PHYSIOLOGIC CHARACTERISTICS

Abstract

Frog fundic mucosas mounted in Ussing chambers between HCO3--buffered nutrient and unbuffered secretory solutions solutions were exposed to 1 M NaCl on the mucosal surface for 10 min. After washing and return to control solutions, transmucosal potential difference, short-circuit current and tissue electrical resistance decreased markedly, but within 6 h these measurements had gradually returned to almost control values. A net luminal alkalinization occurred during the 1st 4 h, changing into a net acid secretion of .apprx. 1.1 .mu.mol .cntdot. cm-2 .cntdot. h-1 at 6 h. Histamine increased H+ secretion in all tissues at 8 h. In 7 metiamide-treated tissues, an average alkaline flux of .apprx. 0.75 .mu.mol .cntdot. cm-2 .cntdot. h-1 was obtained during the 1st 4 h after damage, decreasing to .apprx. 0.40 .mu.mol .cntdot. cm-2 .cntdot. h-1 during the ensuing 4 h. With HCO3--free nutrient solution (n = 7) luminal alkalinization was decreased by .apprx. 80% 2-4 h after injury. After 1 M NaCl, the surface epithleium and gastric pit cells were destroyed and partially lifted from the gastric glands. The lamina propria between the remaining intact glands was open to the lumen or contiguous with the damaged mass of cells and mucus. During the 6 h after damage, there was a gradual process of restitution of epithelial integrity, beginning with squamous-shaped cells that appeared to be migrating from the glands and ultimately concluding with complete epithelialization by cuboidal and columnar cells. Typical junctional complexes were present between adjacent epithelial cells. The uniformity of the restoration process was such that it was possible to predict blindly in toluidine blue-stained semithin sections whether the recovery stage was short (30 min or less), intermediate (1-2 h) or advanced (4-6 h). There is a very intimate correlation between the restoration of epithelial continuity and the reestablishment of secretory and electrical activity of frog gastric mucosa damaged by hypertonic NaCl in Ussing chambers.