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Localization of G Protein -Subunits in the Human Fetal Adrenal Gland¹

Service of Endocrinology (L.B., E.C., N.G.-P.), Department of Biochemistry (J.-G.L), Faculty of Medicine, University of Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4

Address all correspondence and requests for reprints to: Dr. Nicole Gallo-Payet, Service of Endocrinology, Faculty of Medicine, Université de Sherbrooke, 3001, 12th Avenue North, Sherbrooke, Québec, Canada J1H 5N4. E-mail: n.gallo{at}courrier.usherb.ca

The aim of the present study was to investigate the presence and localization of the main G protein -subunits in the human fetal adrenal gland during the second trimester of gestation. Immunofluorescence studies conducted on sections from frozen glands obtained immediately after therapeutic abortion indicated that the s subunit of the heterotrimeric G_s protein was detected in all adrenal cell types, except for endothelial cells. The other -subunits had a more specific pattern of distribution. Indeed, the i1–2 protein was restricted to the definitive zone, whereas i3 labeling was mainly expressed in the fetal zone. The q protein subunit was localized in vascular endothelial cells at the periphery of the adrenal gland and in fetal cells at the center. Finally, chromaffin cells expressed s, q, and o1, but not o2 nor i. Altogether, these results indicate that the human fetal adrenal gland is not only unique in its particular morphology and expression of steroidogenic enzymes, but also by the differential expression of G protein -subunits. Such cell specific distribution in glands from midgestational fetuses may account for the absence or the different responses to stimuli, when compared with the adult adrenal gland.