L. Breault

Angiotensin II receptors in the human adrenal gland

In the present study, we have characterized distribution and pharmacological properties of angiotensin II (Ang II) receptors in human adrenals frozen immediately after removal. Autoradiographic studies indicate that Ang II receptors are present throughout the gland. Co-incubations with DUP 753, a specific antagonist of the AT1 receptor, and with PD 123319, a specific antagonist of the AT2 receptor, reveal that Ang II receptors are mainly of type 2. The AT1 receptors are detected after 16 weeks of gestation at the periphery of the gland. Competition studies and Scatchard analysis reveal a homogenous population of high affinity AT2 binding sites (Kd = 0.68 +/- 0.1 nM). Binding capacities decrease from 1080 +/- 304 fmol/mg protein at 14 weeks to 275 +/- 55 fmol/mg protein at 21 weeks. These results differ from those obtained in adult glands where autoradiographic studies reveal that the AT1 receptors are found mainly in the zona glomerulosa and AT2 receptors mainly in the medulla. These data suggest that the AT2 receptors could be involved in the morphological or functional differentiation of the human fetal adrenal gland.

Occurrence and Effect of PACAP in the Human Fetal Adrenal Gland

Abstract: In the study reported in this paper, we characterized PACAP in the human fetal adrenal gland and we investigated the effect of PACAP on steroid secretion from cultured fetal adrenal cells. The adrenal gland from 20‐week‐old fetuses contained substantial concentrations of PACAP‐immunoreactive material (88.6 ng/g wet tissue). HPLC analysis of adrenal extracts revealed the presence of both PACAP27 and PACAP38, the latter being the predominant form. Incubation of cultured fetal adrenal cells with PACAP38 (10−7 M) significantly increased cortisol and DHEAS secretion. Administration of the β‐adrenoreceptor agonist isoproterenol mimicked the stimulatory effect of PACAP on both steroid secretion whereas preincubation of fetal cells with the β‐adrenoreceptor antagonist propranolol suppressed the steroidogenic effect of PACAP. These data, together with the observation that PACAP receptors are exclusively located on chromaffin cells, suggest that, in the fetal human adrenal gland, the effect of PACAP on steroid secretion is mediated via the local release of catecholamines.

Identification of a novel secretogranin II-derived peptide in the adult and fetal human adrenal gland

Molecular cloning of secretogranin II (SgII) in different species has revealed the existence of a highly conserved 66-amino acid peptide (EM66) flanked by preserved pairs of basic residues. In the present study we have localized and characterized EM66 in the human adrenal gland. A fusion protein containing the human EM66 peptide was produced in E. coli and used to raise polyclonal antibodies in rabbits. Immunohistochemical staining of human adrenal slices revealed intense labeling of adrenochromaffin cells in the adult and fetal gland. HPLC analysis of adrenal extracts showed the presence of an immunoreactive peak exhibiting the same retention time as recombinant EM66 in both adult and fetus. These data demonstrate that post-translational processing of SgII actually generates a novel peptide in the human adrenal gland. The conservation of the sequence of EM66 in vertebrates and the occurrence of the mature peptide during early ontogenesis of the human adrenal gland strongly suggest that EM66 could exert physiological activities.

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

The aim of the present study was to investigate the presence and localization of the main G protein α-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 αs subunit of the heterotrimeric Gs protein was detected in all adrenal cell types, except for endothelial cells. The otherα -subunits had a more specific pattern of distribution. Indeed, theα i1–2 protein was restricted to the definitive zone, whereas αi3 labeling was mainly expressed in the fetal zone. The αq 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 αs, αq, and αo1, but not αo2 nor αi. 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 differ...

Comparative effects of ACTH, PACAP, and VIP on fetal human adrenal cells

ACTH is a well-known stimulus of human adrenal cells, both in the adult and in the fetus. Two other stimuli, acting via the cAMP pathway, are also involved in the regulation of steroidogenesis and growth of the adult gland, the Pituitary Adenylate Cyclase Activating Peptide (PACAP) and the Vasoactive Intestinal Polypeptide (VIP). The aim of this study was to compare the effects of the three peptides on cAMP production and to investigate their possible effect on cytoskeletal organization in the different cell types present in the human fetal adrenal gland, i.e steroidogenic cells and chromaffin cells. Using phalloidin-rhodamine labeling of actin microfilaments, we observed that VIP and ACTH strongly affect cytoskeletal organization. Application of ACTH rapidly induces steroidogenic cells to elaborate fillopodia and junctions with neighboring cells. Application of VIP strongly stimulates the chromaffin cells to elaborate neurite-like extensions, suggesting that the effects of VIP could be, as in adult glands, mediated by the adrenal medulla.

Ontogeny of 5-HT4 receptors in the human adrenal gland

1In the human adrenal gland, the occurrence of serotonin (5-HT)-like immunoreactivity has been observed in mast cells and the presence of 5-HT in adrenal extracts has been confirmed by HPLC analysis coupled to electrochemical detection (1). In vitro studies have shown that 5-HT stimulates cortisol and aldosterone secretion from isolated adrenocortical cells through 5-HT4 receptors, positively coupled to adenylyl cyclase and calcium influx (2). Concurrently, it has been demonstrated that 5-HT4 receptor agonists stimulate aldosterone secretion in healthy volunteers and in patients with aldosterone disorders (3). The aim of the present study was to investigate the distribution of 5-HT4 receptors in the fetal human adrenal gland during the second trimester of gestation. Adrenal glands were obtained from 14- to 20-week-old fetuses at the time: of therapeutic abortion. The localization and density of 5-HT4 receptors were studied by in vitro quantitative autoradiography. Adrenal slices were incubated with the highly specific 5-HT4 receptor antagonist [3H]GR1 13808 (0.1-0.2 nM) in the