Seladin-1 (KIAA0018) gene is the seventh most highlyexpressed gene in the adult adrenal gland, along with genes coding for steroidogenic enzymes. The aim of the present study was to investigate the localization of the Seladin-1 protein in control and ACTH-treated rat adrenal glands and to verify whether Seladin-1 is involved in secretion. Immunofluorescence studies revealed that Seladin-1 was localized principally in the zona fasciculata, cytoplasm, and nucleus. Expression of Seladin-1 was increased by ACTH treatment, in vivo and in culture conditions. Subcellular fractionation offasciculata cells showed that Seladin-1 was mainly present in the nucleus, membrane, and cytoskeleton fractions and, to a lesser extent, in the cytosol. ACTH treatment decreased Seladin-1 expression in the cytosol, with a concomitant increase in the nuclear fraction. In the glomerulosa and fasciculata cells in culture, ACTH induced a relocalization of Seladin-1 into specific nuclear regions. This ACTH-induced relocalization was abrogated by the pre-treatment of cells with 75 nM U18666A (an inhibitor of Seladin-1). In addition, fasciculata cells exhibited an increase in the basal level of steroid secretion when cultured in the presence of U18666A (25 and 75 nM), although ACTH-induced secretion was decreased. In summary, the present study demonstrates that the protein expression of Seladin-1 is more abundant in fasciculata cells than in glomerulosa cells and that the ACTH treatment increases both expression and nuclear localization of the protein. Results also suggest that depending on its cellular localization, the Δ24-reductase activity of Seladin-1 may play a major role in steroid secretion in the adrenal gland.
Marie-Claude Battista, Claude Roberge, Mélissa Otis and Nicole Gallo-Payet
Mélissa Otis, Shirley Campbell, Marcel D Payet and Nicole Gallo-Payet
The expression of main extracellular matrix (ECM) and their integrins were studied in the adult rat adrenal gland. Collagen I, IV (CI, CIV), laminin (LN) and fibronectin (FN) expression was observed surrounding each glomerulosa cell and as long fibrils between the cords of fasciculata cells. In the medulla, FN was present around chromaffin cells or bordering blood vessels. Integrin α2, α3 and α5 were present mainly in the cortex, while α1 was present in the medulla. In culture, all ECM favoured proliferation of both glomerulosa and fasciculata cells, while protein synthesis was lower on FN and LN in glomerulosa cells. CIV promoted ACTH-induced proliferation whereas FN favoured ACTH-induced protein synthesis in glomerulosa cells. Except for LN, ECM increased expression of 3β-hydroxysteroid dehydrogenase and enhanced basal aldosterone, although corticosterone secretion was only enhanced by CI and CIV. In fasciculata cells, the potency of ACTH-induced cAMP production was lower on ECM, compared with plastic. Moreover, ACTH, but not ECM, activated mitogenic-activated protein kinase p38 and stress-activated protein kinases. Glomerulosa and fasciculata cells grown on CI and CIV had a polygonal morphology, while cells grown on LN appeared as clusters of small rounded cells. On FN, the glomerulosa cells exhibited polygonal morphology while fasciculata cells appeared as clusters of small rounded cells. Together, these results indicate that ECM modulates basal and ACTH-induced cell functions, with FN, CI and CIV specifically favouring steroid secretion, as opposed to LN which inhibits secretion while promoting proliferation.
Karine Bibeau, Mélissa Otis, Jean St-Louis, Nicole Gallo-Payet and Michèle Brochu
In low sodium-induced intrauterine growth restricted (IUGR) rat, foetal adrenal steroidogenesis as well as the adult renin–angiotensin–aldosterone system (RAAS) is altered. The aim of the present study was to determine the expression of cytochrome P450 aldosterone synthase (P450aldo) and of angiotensin II receptor subtypes 1 (AT1R) and 2 (AT2R) in adult adrenal glands and whether this expression could be influenced by IUGR and by high-salt intake in a sex-specific manner. After 6 weeks of 0.9% NaCl supplementation, plasma renin activity, P450aldo expression and serum aldosterone levels were decreased in all groups. In males, IUGR induced an increase in AT1R, AT2R, and P450aldo levels, without changes in morphological appearance of the zona glomerulosa (ZG). By contrast, in females, IUGR had no effect on the expression of AT1R, but increased AT2R mRNA while decreasing protein expression of AT2R and P450aldo. In males, salt intake in IUGR rats reduced both AT1R mRNA and protein, while for AT2R, mRNA levels decreased whereas protein expression increased. In females, salt intake reduced ZG size in IUGR but had no affect on AT1R or AT2R expression in either group. These results indicate that, in response to IUGR and subsequently to salt intake, P450aldo, AT1R, and AT2R levels are differentially expressed in males and females. However, despite these adrenal changes, adult IUGR rats display adequate physiological and adrenal responses to high-salt intake, via RAAS inhibition, thus suggesting that extra-adrenal factors likely compensate for ZG alterations induced by IUGR.