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ABSTRACT
The rate of blood flow through the intact adrenal gland is closely linked to steroid hormone secretion, and although the mechanism involved is unknown, it is thought to involve secretory products of the vascular endothelium.
In dispersed cell preparations, endothelin-1 and -3 both caused a dose-dependent and highly sensitive increase in steroid secretion by zona glomerulosa and zona fasciculata cells of the rat and human adrenal cortex. In addition, when the perfused rat adrenal was stimulated with ACTH, significant increases in steroid secretion and perfusion medium flow rate were accompanied by significantly increased secretion of immunoreactive endothelin into the adrenal vein. It is proposed that endothelin has a role in mediating the adrenocortical response to ACTH stimulation.
Journal of Endocrinology (1991) 128, 275–280
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Introduction
A newly discovered class of messenger molecules appears to be concerned in a whole variety of biological functions in vertebrates: gaseous in nature, and thought of until recently as little more than toxic pollutants, these molecules have in fact become of considerable scientific importance. The notion of gases acting as biological signals was initially surprising, when it was proposed that nitric oxide (NO), or a closely related thiolic derivative, could account for the vasodilatory activity of endothelium-derived relaxing factor (EDRF) (Palmer et al. 1987). A rapidly growing body of evidence has since consistently indicated that NO or a related substance plays a role in such diverse functions as long-term potentiation (LTP), a neurophysiological model for the processes of learning and memory, as well as immune responses, and the autonomie activity underlying gut relaxation and penile erection subserved by non-adrenergic non-cholinergic (NANC) peripheral fibres (Moneada et al. 1991). Furthermore, there
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ABSTRACT
The effects of an elasmbranch cardiac C-type natriuretic peptide (dogfish CNP-22) on arterial blood pressure were investigated in vivo in chronically cannulated dogfish Scyliorhinus canicula and in vitro by a myographic technique using the distal part of the first branchial artery. In-vivo dogfish CNP-22 caused a dose-dependent reduction in mean arterial blood pressure which was much more potent than that of α-human ANP. In-vitro dogfish CNP-22 also caused a dose-dependent relaxation which was independent of the endothelium. These results are in marked contrast to those obtained in similar studies on other vertebrate species in which CNP exhibited only mild hypotensive effects compared to both atrial and brain natriuretic peptides. This study indicates the importance of using homologous peptides in determing the physiological role of natriuretic peptides in non-mammalian vertebrates.
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To many attending the 6th Joint Meeting of British Endocrine Societies at the University of Warwick in March 1987, one symposium appeared perhaps somewhat unorthodox in its subject area, being juxtaposed alongside more clearly defined specialities such as the Oestrogen Receptor, Calcium-Regulating Hormones and Adrenal Gland. The Symposium itself (Journal of Endocrinology, 1987) covered a broad spectrum of endocrinology and gave refreshing views of contemporary endocrinology. These included:
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(1) a discussion of current morphological methods for identifying hormones and their receptors;
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(2) a critical analysis of so-called ectopic hormones;
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(3) a provocative hypothesis regarding the evolutionary origin of the neuroendocrine system;
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(4) the current status and likely direction of investigation into the, at present, unidentified endothelium-derived relaxing factor (EDRF).
All of these communications, dealing with rapidly moving areas, gave their audience insight into some philosophies that underly much of contemporary endocrinology. It is apt to preface a commentary on this Symposium by
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SUMMARY
The age at which cadmium salts first cause an increase in vascular permeability in the rat testis has been studied using Evans blue as a marker.
Cadmium-induced blueing of the testis, indicative of increased vascular permeability, first occurred on the 9th day of life, at about the same time as the descent of the testes and an apparent increase in the amount of 3β-hydroxysteroid dehydrogenase-positive tissue. The increased permeability coincided approximately with a rise in the alkaline phosphatase reactivity of the testicular capillary endothelium. It is suggested that the onset of sensitivity of the testicular blood vessels to cadmium salts is related in some way to the onset of androgen production by the testes.
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Abstract
The monoclonal antibody 6313/G2 raised against the mammalian type I (AT1) angiotensin II (Ang II) receptor (Ang II-R) also recognises a component in teleost (eel) tissue preparations that binds radiolabelled Ang II, and has an isoelectric point (pI) of 6·5 and molecular mass of 75 kDa. Immunohistochemical analysis using this antibody showed specific binding sites in eel intestine, kidney, gill and liver sections.
The same antibody was used here to evaluate the presence and distribution of Ang II-R in target tissues of the Antarctic teleost icefish (Chionodraco hamatus).
Immunocytochemistry of intestine and gill sections showed that the antibody bound to uniformly distributed intracellular sites and cell surface membranes in absorptive cells in the intestine and chloride and pavement cells in the gills. It also stained endothelium and both the longitudinal and circular layers of smooth muscle cells in the intestine. In the kidney, only the tubules in the trunk stained positively while the head (atubular part of the kidney) was negative. In kidney tubules, in contrast with other tissues, the receptor was most concentrated in the cytoplasm underlying the basolateral membranes, with somewhat weaker staining beneath the apical cell membrane. Immunoblotting identified a single component from trunk kidney preparations that focused at pI 5·9 in isoelectric focusing gels and showed a molecular mass of 75 kDa in SDS–polyacrylamide gels.
The data suggest that, as in other teleosts, Ang II has a physiological role in the icefish.
Journal of Endocrinology (1997) 154, 193–200
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ABSTRACT
Lipase activity in homogenates of guinea-pig adrenals was studied under conditions which exclude the hormone-sensitive lipase/cholesterol ester hydrolase. Antibody inhibition and chromatography on heparin–Sepharose showed that most of the activity was due to lipoprotein lipase (LPL), and that there was only a small amount of hepatic lipase activity. Northern blot analysis of total RNA demonstrated the same three adrenal LPL mRNA species (1·8, 3·1 and 3·5 kb) as were found in adipose tissue and heart. Hence, at least part of the LPL activity in adrenals is due to enzyme synthesized within the tissue. Immunolocalization showed that LPL was associated with the endothelium of blood vessels throughout the gland. In addition, there was cytoplasmic immunoreaction, suggesting that lipase was synthesized in a subpopulation of cells in the transitional zone between the fasciculata and reticularis layer of the cortex, particularly over lipid-filled cells. There was also intense immunofluorescence over scattered cells in the adrenal medulla. Treatment with an ACTH analogue depot (20 IU, i.m.) for 11 days induced a 12-fold increase in serum cortisol and increased adrenal weight 2·2-fold. The treatment induced increases in LPL mRNA (about twofold), LPL activity and in the number of cells in the adrenal cortex which gave an immunoreaction for LPL.
Journal of Endocrinology (1991) 129, 213–220
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ABSTRACT
The aim of this study was to investigate the localization of endothelin-like immunoreactivity (ET-IR) in human placenta, chorion and amnion and to compare the endogenous concentration of immunoreactive endothelin (ET) in these tissues before and after the onset of labour. ET-IR was detected in the endothelium of stem vessels in placental villi, as well as in decidual stromal cells in the basal maternal plate, by immunocytochemistry using a primary polyclonal rabbit antibody. A specific radioimmunoassay was used to detect endogenous concentration of ET in homogenized placental tissues. The endogenous concentration of ET-IR was significantly greater in amnion than in chorion and placenta (amnion 249 ±13 fmol/g; chorion 190 ±11 fmol/g; placenta 169±14 fmol/g; means ± s.e.m.; n = 12; P < 0·01). No significant difference was seen before or after the onset of labour. The detection of ET-IR in placenta, chorion and amnion suggests that the ETs may play a role in the paracrine control of human uterine function.
Journal of Endocrinology (1991) 131, 507–511
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SUMMARY
The distribution of dehydrogenases acting on 3α-, Δ5-3β-, 3β-, 11β-, 16β(androgen)-, 16β(oestrogen)-, 17β-, and 20β-hydroxysteroids in the placentae and foetal membranes of the horse, sheep, goat, cat, dog, ferret, rat, rabbit, guinea-pig and man at various stages of pregnancy is described, and some attempt is made to relate their presence in the tissues with their function.
Δ5-3β-Hydroxysteroid dehydrogenase, of particular interest in view of its important function in steroid biosynthesis, was found in the trophoblast of the horse, cat, dog and man, in the thickened maternal endothelium of the ferret placenta, in the trophoblastic giant cells of the rat, and in isolated cells in the uterine lumen of the guinea-pig in early pregnancy. The enzyme was absent from all other sites examined. Correlation is sought between the distribution of this enzyme, the steroid hormone requirements for the maintenance of pregnancy after ovariectomy, and the chemical processes of steroid production by the placentae of the species examined.
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In this study, we investigated the role of intercellular adhesion molecule-2 (ICAM2) in the testis. ICAM2 is a cell adhesion protein having important roles in cell migration, especially during inflammation when leukocytes cross the endothelium. Herein, we showed ICAM2 to be expressed by germ and Sertoli cells in the rat testis. When a monospecific antibody was used for immunolocalization experiments, ICAM2 was found to surround the heads of elongating/elongated spermatids in all stages of the seminiferous epithelial cycle. To determine whether ICAM2 is a constituent of apical ectoplasmic specialization (ES), co-immunoprecipitation and dual immunofluorescence staining were performed. Interestingly, ICAM2 was found to associate with β1-integrin, nectin-3, afadin, Src, proline-rich tyrosine kinase 2, annexin II, and actin. Following CdCl2 treatment, ICAM2 was found to be upregulated during restructuring of the seminiferous epithelium, with round spermatids becoming increasingly immunoreactive for ICAM2 by 6–16 h. Interestingly, there was a loss in the binding of ICAM2 to actin during CdCl2-induced germ cell loss, suggesting that a loss of ICAM2–actin interactions might have facilitated junction restructuring. Taken collectively, these results illustrate that ICAM2 plays an important role in apical ES dynamics during spermatogenesis.
