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GABA uptake by antral mucosa
195
GABA UPTAKE BY ANTRAL MUCOSA P.ATHANASSOPOULOS, A. VARRO and G.J.DOCKRAY Physiological Laboratory, University of Liverpool, Liverpool, UK. Gastrin and somatostatin-containing endocrine cells of the antra] mucosa are reported to take up the neurotransmitter y-amino butyric acid (GABA). We h~ve examined whether uptake is influenced by physiological factors that are known to modulate antral endocrine cell function. Antra] mucosal segments from rats fed 7d libitum, fasted for 48hr, or treated with omeprazole (400 ~mol/kg, 24hr), were incubated at 37°C in modified Krebs-Ringer medium containing 1.67 ~Ci/m] [3H] GABA and gassed with 9 5 % 0 2 and 5% CO 2. After incubation, tissue samples wtre extracted in water, centrifuged and aliquots of supernatant counted and protein determined. There was linear uptake of [3H] GABA for up to 4hr by antral mucosa. Addition of unlabelled GABA, or of the GABA-transport inhibitor diamino butyric acid, produced graded inhibition of uptake. In fasted rats, GABA uptake was significantly increased compared with rats fed ad libitum (26.8 + 3.4 vs 48.7 + 6.1 epm x 103/rag protein, over 2hr, p<0.05). In contrast, in omeprazole-treated rats, the uptake of GABA was similar to controls. CONCLUSION. l. There is specific GABA uptake by antral mucosa. 2. Withdrawal of food increases GABA uptake, tut inhibition of acid secretion for 24hr has no effect. 3. Modulation of GABA turnover is part of the functional response of the antral mucosa to luminal stimuli. AN ELECTRON MICROSCOPICAL STUDY OF THE OXYNTICOPEPTIC TELEOST SPECIES Gadus morhua AND Oncorhynchus mykiss, AND HISTAMINE STIMULATED PHASES. P.BOMGREN, S.EINARSSON, and A-C.J~NSSON, University Medicinaregatan 18, 413 90 G~TEBORG, SWEDEN.
CELLS IN TWO DURING BASAL of
G6teborg
The morphology of the acid secreting stomach mucosa in cod and rainbow trout was studied with electron microscopy during a basal condition and after histamine stimulation. The stimulated acid secretion was measured by pH titration of an isolated stomach mucosa. The mucosa stabilized its basal acid secretion after 70-90 min, whereafter histamine was added. When a m a x i m a l answer to histamine was seen the mucosa was fixed for electron microscopy, postfixation was done with 1% Os04, stained With 0.5% uranyl and finally embedded in epon/durcupan. The control or basal specimen was taken from the same fish (cod) that was used for histamine stimulation, fixation was done within a few min after dissecting out the stomach. The oxynticopeptic cells of the two teleosts contained many electron dense vesicles, tubolovesicles, apical microvilli and numerous mitochondria. There was a dramatic change in morphology after stimulation evident by an increased number of apical microvilli and especially an increased luminal size. No differences in the number of electron dense vesicles could be seen after stimulation. No clear differences could be seen ultrastructurally betweeen the saltwater (cod) and the freshwater (rainbow trout) fish. The study indicates that acid and pepsinogen is stimulated by different mechanisms.
GABA UPTAKE BY ANTRAL MUCOSA P.ATHANASSOPOULOS, A. VARRO and G.J.DOCKRAY Physiological Laboratory, University of Liverpool, Liverpool, UK. Gastrin and somatostatin-containing endocrine cells of the antra] mucosa are reported to take up the neurotransmitter y-amino butyric acid (GABA). We h~ve examined whether uptake is influenced by physiological factors that are known to modulate antral endocrine cell function. Antra] mucosal segments from rats fed 7d libitum, fasted for 48hr, or treated with omeprazole (400 ~mol/kg, 24hr), were incubated at 37°C in modified Krebs-Ringer medium containing 1.67 ~Ci/m] [3H] GABA and gassed with 9 5 % 0 2 and 5% CO 2. After incubation, tissue samples wtre extracted in water, centrifuged and aliquots of supernatant counted and protein determined. There was linear uptake of [3H] GABA for up to 4hr by antral mucosa. Addition of unlabelled GABA, or of the GABA-transport inhibitor diamino butyric acid, produced graded inhibition of uptake. In fasted rats, GABA uptake was significantly increased compared with rats fed ad libitum (26.8 + 3.4 vs 48.7 + 6.1 epm x 103/rag protein, over 2hr, p<0.05). In contrast, in omeprazole-treated rats, the uptake of GABA was similar to controls. CONCLUSION. l. There is specific GABA uptake by antral mucosa. 2. Withdrawal of food increases GABA uptake, tut inhibition of acid secretion for 24hr has no effect. 3. Modulation of GABA turnover is part of the functional response of the antral mucosa to luminal stimuli. AN ELECTRON MICROSCOPICAL STUDY OF THE OXYNTICOPEPTIC TELEOST SPECIES Gadus morhua AND Oncorhynchus mykiss, AND HISTAMINE STIMULATED PHASES. P.BOMGREN, S.EINARSSON, and A-C.J~NSSON, University Medicinaregatan 18, 413 90 G~TEBORG, SWEDEN.
CELLS IN TWO DURING BASAL of
G6teborg
The morphology of the acid secreting stomach mucosa in cod and rainbow trout was studied with electron microscopy during a basal condition and after histamine stimulation. The stimulated acid secretion was measured by pH titration of an isolated stomach mucosa. The mucosa stabilized its basal acid secretion after 70-90 min, whereafter histamine was added. When a m a x i m a l answer to histamine was seen the mucosa was fixed for electron microscopy, postfixation was done with 1% Os04, stained With 0.5% uranyl and finally embedded in epon/durcupan. The control or basal specimen was taken from the same fish (cod) that was used for histamine stimulation, fixation was done within a few min after dissecting out the stomach. The oxynticopeptic cells of the two teleosts contained many electron dense vesicles, tubolovesicles, apical microvilli and numerous mitochondria. There was a dramatic change in morphology after stimulation evident by an increased number of apical microvilli and especially an increased luminal size. No differences in the number of electron dense vesicles could be seen after stimulation. No clear differences could be seen ultrastructurally betweeen the saltwater (cod) and the freshwater (rainbow trout) fish. The study indicates that acid and pepsinogen is stimulated by different mechanisms.