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  • Author: G Rosselin x
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*Laboratoire de Physiologie du Développement, Tour 23/33, Université Paris VII, 2 Place Jussieu, 75005 Paris, France and †Unité de Recherches de Diabétologie et d'Etudes Radio-Immunologlques des Hormones Protéiques, U.55 (INSERM), Hôpital Saint-Antoine, 184 Rue du Faubourg Saint-Antoine, 75012 Paris, France

(Received 1 November 1977)

Experimental prolonged gestation in the rat results in a reduction in the amounts of insulin and glucagon accumulated in the pancreas, a low level of insulin in the plasma and a sharp depletion of hepatic glycogen stores (Portha, Rosselin & Picon, 1976). Moreover, in the liver of the postmature foetus the activities of the main glyconeogenic enzymes, glucose-6-phosphatase and phosphoenolpyruvate carboxykinase, are increased (Portha, Le Provost, Picon & Rosselin, 1978). The present study was undertaken to investigate the effects of glucagon in the circulation on these processes.

Gestation was prolonged by s.c. administration of progesterone to the mother (2·5 mg/rat) once daily on days 20·5, 21·5

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G Skoglund, A Basmaciogullari, B Rouot, JC Marie and G Rosselin

G protein alpha-subunits are involved in the transduction of receptor-mediated regulation of insulin and glucagon secretions. To get further insight into the status of G proteins in alpha- and beta-cells of the Langerhans islets, we have used immunohistochemistry to study the distribution of alpha-subunits in pancreas sections from the rat. Our results show that only insulin-immunoreactive beta-cells display immunoreactivity for selective antibodies directed against the different members of the Galphas and Galpha12-families (alphas, alphaolf, and alpha12, alpha13 respectively). Immunoreactivities for antibodies directed against members of the Galphaq- and Galphai-families showed a more diverse localization: alpha11 and alphao2 were only detected in glucagon-immunoreactive alpha-cells, whereas alphai1 was detected in all beta-cells but only in a few alpha-cells. Even though beta-cells showed immunoreactivities for alphao-non-isoform-selective antibodies, we could not identify the isoform(s) present using selective alphao1 and alphao2 antibodies. Other members of the Galphai- and Galphaq-families (alphai3, alphat2, alphaz and alphaq) were detected in both alpha- and beta-cells. In conclusion, our findings demonstrate a clear difference in the localization of G protein alpha-subunits between alpha- and beta-cells, suggesting the involvement of specific receptor transduction pathways for the neuronal/hormonal regulation of alpha- and beta-cell functions.