GABA-A-mediated gastrin release induced by baclofen in the isolated vascularly perfused rat stomach

Summary In order to investigate the role of peripheral GABA-B receptors, the effects of the putative GABA-B agonist baclofen on immunoreactive gastrin release from an isolated vascularly perfused rat stomach preparation were examined. The vascular infusion of baclofen at graded concentrations induced a dose-dependent increase in gastrin release; this was unaffected by the GABA-B antagonist delta-aminovaleric acid, but was fully prevented by the selective GABA-A antagonist bicuculline as well as by atropine or tetrodotoxin. These results suggest that the stimulant effects of baclofen are mediated by nervous cholinergic structures, associated with GABA-A receptors, and indicate that this GABA-B agonist must be regarded as a partial agonist of peripheral GABA-A receptors.     

GABA-A-mediated gastrin release induced by baclofen in the isolated vascularly perfused rat stomach

In order to investigate the role of peripheral GABA-B receptors, the effects of the putative GABA-B agonist baclofen on immunoreactive gastrin release from an isolated vascularly perfused rat stomach preparation were examined. The vascular infusion of baclofen at graded concentrations induced a dose-dependent increase in gastrin release; this was unaffected by the GABA-B antagonist delta-aminovaleric acid, but was fully prevented by the selective GABA-A antagonist bicuculline as well as by atropine or tetrodotoxin. These results suggest that the stimulant effects of baclofen are mediated by nervous cholinergic structures associated with GABA-A receptors, and indicate that this GABA-B agonist must be regarded as a partial agonist of peripheral GABA-A receptors.     

Differential inhibitory effects of noradrenaline upon insulin secretion by the isolated perfused pancreas of the rat

Summary Responses of basal and glucose-induced secretion phases of the isolated perfused pancreas of the rat to graded doses of noradrenaline (NA) are described. Maximal inhibition of basal secretion was achieved at [NA]=40, ng/100 ml; at [NA]=80 ng/100 ml, the 1st phase of glucose induced secretion was abolished; at [NA]=100 ng/100 ml the 2nd phase was abolished. At [NA]40 ng/100 ml basal secretion was less sensitive to NA inhibition than glucose induced output.Acknowledgment. The authors are most grateful to Mr J. Stevenson for advice upon and assistance with statistical analysis of data.     

Changes induced by the acute administration of iodide on secretion of iodinated components by the rat thyroid gland perfused in situ

Résumé Nous avons étudié l'effet de l'iodure 127 (10^–3 et 10^–4 M) sur la sécrétion de T₄ ^*, T₃ ^* et –I^* par la thyroïde de rat, prémarquée à l'iode 131 et perfusée in situ avec du sang non radioactif contenant 12 mU de TSH/ml. Il n'a pas été noté de changement significatif dans la sécrétion de T₄ ^* ou T₃ ^* jusqu'à 45 min après le début de l'administration d'iodure 127, qu'il y ait ou non du méthimazole (10^–3 M) dans le sang perfusé. Il y avait par contre une augmentation de la sécrétion d'-I^* pendant la perfusion de 10^–3 M d'ïodure, indiquant une décharge d'-I^* pendant la perfusion de 10^–3 M d'ïodure, indiquant une décharge d'-I^* de provenance intrathyroïdienne. Cet effet est similaire à celui noté auparavant pendant le perfusion de 10^–3 M de ClO ₄ ^– .     

Stimulation of glycoprotein secretion in dispersed rat submandibular gland acini by cystic fibrosis serum

Summary Acini were enzymatically dissociated from rat submandibular gland and their mucous glycoproteins radiolabelled with¹⁴C-glucosamine. Sera from cystic fibrosis patients stimulated the release of labelled TCA/PTA — insoluble material from the cultured acinar cells to a significantly higher degree than did control sera.This work was supported by the Canadian Cystic Fibrosis Foundation and the Sellers Foundation.     

Effects of corpora cardiaca extract,furosemide and ion substitution on sodium and chloride flux in perfused Malpighian tubules ofLocusta

Treatment with the co-transport inhibitor, furosemide decreased³⁶Cl^– flux across perfused Malpighian tubules ofLocusta. However, exclusion of³⁶Cl^– from the bathing medium had not effect on²²Na⁺ flux whereas substitution of bathing medium Na⁺ by K⁺ increased³⁶Cl^– flux. Diuretic extract of corpora cardiaca increased²²Na⁺ (by 106%) and³⁶Cl^– (by 335%) fluxes differentially.     

Effect of acetone on VLDL secretion by the isolated rat liver

Summary High acetone levels occur in uncontrolled diabetes and after isopropanol administration to rats. In both conditions, very low density lipoproteins (VLDL) secretion is depressed. Acetone, however, failed to affect the VLDL secretion rate by the isolated perfused rat liver, suggesting that this metabolite is not involved in impaired VLDL production in diabetes and after isopropanol administration.     

Secretion of high density lipoprotein by the isolated perfused alcoholic rat liver

Summary Chronic alcohol feeding of a low fat diet for 5 weeks led to a slightly raised though statistically non-significant high density liproprotein cholesterol/apoB containing lipoprotein cholesterol ratio in both the fasting rat serum as well as the secretory products of the isolated perfused liver.Acknowledgments. Human RBC was kindly supplied by the Canadian Red Cross. This work was supported by MRC, DISCUS and the Department of National Health and Welfare, Canada. H. L. is the holder of an MRC studentship.     

Effect of acetone on VLDL secretion by the isolated rat liver.

High acetone levels occur in uncontrolled diabetes and after isopropanol administration to rats. In both conditions, very low density lipoproteins (VLDL) secretion is depressed. Acetone, hoever, failed to affect the VLDL secretion rate by the isolated perfused rat liver, suggesting that this metabolite is not involved in impaired VLDL production in diabetes and after isopropanol administration.     

Formation of gigantic mitochondria in hypoxic isolated perfused rat hearts

Zusammenfassung Herzen gesunder, erwachsener Ratten wurden mit Krebs-Henseleit-Bikarbonatlösung durchströmt (95% O₂5% CO₂). Bei künstlich herbeigeführter Hypoxie (95% N₂5% CO₂) erschienen die Herzmitochondrien innerhalb von 7 min bedeutend vergrössert und zu 25% miteinander verschmolzen.     

Metaplasia in male rat reproductive accessory glands induced by neonatal estrogen treatment

Résumé L'injection de larges doses d'estrone à des rats mâles au début de la période postnatale cause une stratification dans l'épithélium des glandes de coagulation et dans les vésicules séminales. Cette métaplasie a persisté 11 mois après la dernière injection d'estrone.

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Supported by research grants from the Ministry of Education of Japan. I thank Prof.T. Kusama andK. Takewaki, University of Tokyo, for valuable advices during the course of the experiments.