Metabolism Of Corticosterone Research Articles

11β‐HYDROXYSTEROID DEHYDROGENASE TYPE I ENZYME IN THE HEARTS OF NORMOTENSIVE AND SPONTANEOUSLY HYPERTENSIVE RATS

1. The enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) converts glucocorticoids to their inactive 11-keto metabolites. The ubiquitous expression of the NADP-dependent isoform (11 beta HSD1) suggest an important role in modulating glucocorticoid action, but little is known about 11 beta HSD1 gene expression and enzymatic activity in the rat heart. 2. In the present study rat cardiac 11 beta HSD1 activity and ontogeny of gene expression have been characterized. The addition of NADP, but not NAD, to heart homogenates resulted in significant increases in the metabolism of both corticosterone and cortisol, with the former substrate displaying far greater metabolism. Both 11 beta HSD1 gene expression and enzyme activity increased in parallel from low levels at 1 week of age to maximal levels at 8 weeks, with no further change by 16 weeks of age. 3. We also compared the activity of 11 beta HSD1 in the hearts of male and female spontaneously hypertensive rats (SHR) with normotensive Wistar-Kyoto (WKY) controls. Enzyme activity in the pooled atria of female SHR was significantly higher than in male SHR atria (7.6 +/- 0.6% conversion of corticosterone vs 4.5 +/- 0.5%; P < 0.05). The left ventricles of female WKY rats contained significantly less 11 beta HSD activity than either male WKY rats or female SHR (8.6 +/- 0.8% conversion vs 17 +/- 1.4 and 13.6 +/- 0.5%, respectively; P < 0.05). In the right ventricle, female WKY rats also had significantly less enzyme activity than either female SHR or male WKY rats (4.9 +/- 0.7 vs 10.0 +/- 1.7 and 10.2 +/- 1.4%; P < 0.05). 4. These results clearly show that the rat heart contains significant amounts of the 11 beta HSD1 enzyme and that this activity is sexually dimorphic. Furthermore, significant differences were observed between a normotensive and hypertensive strain of rat. The relevance of these observations to the aetiology and maintenance of hypertension remains to be explored.

11β-Hydroxysteroid dehydrogenase deficit: a rare cause of arterial hypertension. Diagnosis and therapeutic approach in two young brothers

We report the clinical history and results of endocrine investigations in two brothers born to consanguineous parents, who presented with hypokalemia and arterial hypertension when they were aged 2 and 6 years. The hormonal serum assay results, including extremely low values for aldosterone and plasma renin activity, favored the existence of apparent mineralocorticoid excess. A diagnosis of 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) deficiency was made, based on assays of the hydrogenated urinary metabolites of cortisol and cortisone, as well as of corticosterone and dehydrocorticosterone. Indeed we found a very low rate of urinary elimination of cortisone metabolites: tetrahydrogenated cortisone was reduced to between 0.10 and 30 mumol/24 h, which is 15-100 times lower than the normal rate; hexahydrogenated cortolones alpha and beta were found to be 7- to 20-fold lower than normal levels; and the 11-keto-17-ketosteroid derivatives of cortisone were also reduced. Urinary elimination of the cortisol-reduced metabolites 5 beta- and 5 alpha-tetrahydrogenated cortisol were slightly reduced or normal. These results argue in favor of a deficit in the enzyme 11 beta-HSD, which oxidizes cortisol into cortisone. A moderate defect in the conversion of cortisol into 5 beta-THF compared to normal conversion into 5 alpha-THF was also found. With respect to corticosterone metabolism, we demonstrated the presence of a defect in the oxidation of that steroid into dehydrocorticosterone, also due to the deficit in 11 beta-HSD. Arterial hypertension and hypokalemia were corrected by treatment with dexamethasone, concomitantly with correction of the low aldosterone and plasma renin activity levels. On the other hand, during this treatment, urinary concentrations of the metabolites of cortisol, cortisone and corticosterone were only moderately affected.

Modulation of the Adrenocortical Stress Response in Neotropical Migrants during Autumn Migration

easonal changes in corticosterone metabolism have been implicated in the migratory physiology of passerines. To investigate how this hormone might relate to migra- tory condition in free-living birds, we compared plasma levels of corticosterone in response to capture and handling stress in premigratory and migrating Gray Catbirds (Dumetella car- olinensis). Lean, premigratory catbirds exhibited stress responses typical of other nonlipogenic, nonhyperphagic bird species sampled on the breeding or wintering grounds (i.e. low levels of corticosterone at capture followed by significant increases over I h). In contrast, fat, migratory catbirds sampled later in the season showed significantly higher baseline levels of corticosterone at capture and no significant increase in hormone levels with handling time. We also sampled a group of migrating Yellow-rumped Warblers (Dendroica coronata) at a stopover site. Like catbirds, migrating warblers exhibited an absence of a stress response, with no significant change in corticosterone levels with capture and handling stress. Unlike birds sampled on the breeding grounds, there was no relationship between corticosterone levels at capture and fat scores in premigratory and migratory catbirds, or in the migratory warblers. These results support our Migration-Modulation Hypothesis regarding seasonal changes in corticosterone levels, viz.: (1) an absence of a relationship between fat deposition and baseline corticosterone levels illustrates the permissive nature of the hormone, which remains elevated throughout the migratory period to facilitate hyperphagia and lipogenesis independent of short-term changes in energetic condition; and (2) further elevation of cor- ticosterone in response to acute stress is suppressed during migration to protect skeletal muscle needed for flight. Received 25 April 1995, accepted 14 July 1995.

Corticosterone metabolism and effects on angiotensin II receptors in vascular smooth muscle.

It has been postulated that mineralocorticoids can bind to corticosteroid receptors in the kidney, because glucocorticoids are metabolized to inactive compounds. The present study was performed to delineate glucocorticoid metabolism by rat vascular tissue and to determine the activity of these metabolites. Vascular segments converted 25% to 30% of corticosterone (compound B), the major glucocorticoid in the rat, to 11-dehydrocorticosterone (compound A) but not to aldosterone or 6 beta-hydroxycorticosterone. In cultured vascular smooth muscle cells, 10% of compound B was converted to compound A, whereas > 60% of compound A was converted to compound B. The 11 beta-hydroxysteroid dehydrogenase inhibitor carbenoxolone (1 mumol/L) completely blocked conversion in both directions. Whereas 6 beta-hydroxycorticosterone did not upregulate angiotensin II receptor binding (a marker for corticosteroid action in vascular smooth muscle), compound A caused concentration-dependent upregulation. Compound A was almost (75%) as effective and as potent as compound B in upregulating angiotensin II binding. Upregulation elicited by exposure to compound A persisted in the presence of 1 mumol/L carbenoxolone, which completely prevented the conversion of compound A to compound B. Compound A, even in the presence of carbenoxolone, effected other glucocorticoid actions by inhibiting cell growth and potentiating angiotensin II-stimulated inositol phosphate formation. In summary, compound B and compound A are interconverted in vascular tissue, and the latter displays significant glucocorticoid action. The concentration excess of compound B in the circulation and the activity of its metabolite compound A will make it difficult for mineralocorticoids to gain access to corticosteroid receptors in the vasculature.

Bidirectional activity of 11β-hydroxysteroid dehydrogenase in vascular smooth muscle cells

Endogenous glucocorticoids (GC) can be metabolized through the enzyme 11β-hydroxysteroid dehydrogenase (11β-OHSD); in the rat, corticosterone (B) is converted to its inactive metabolite 11-dehydrocorticosterone (A). Since increased tissue concentrations of GCs may affect blood pressure by potentiating the vasoactive effects of α-adrenergic agonists and possibly other pressors, we studied the metabolism of corticosterone in freshly dissected aortae and cultured vascular smooth muscle cells (VSMC). Incubations were generally conducted for 60 min with 10 −8 M steroid; steroids were isolated and identified by HPLC. In aortic minces stripped of endothelium, the oxo-reductase reaction of A back to B was nearly 4 times greater than the dehydrogenase reaction of B to A (2.8 ± 0.5 × 10 −11 versus 7.3 ± 1.0 × 10 −12 mol/mg protein). This pattern was also seen in cultured VSMC during growth and quiescent states (growth A to B 3.2 ± 0.4 × 10 −12 versus B to A 9.7 ± 0.9 × 10 −13 mol/mg protein; quiescent A to B 8.8 ± 0.1 × 10 −12 versus B to A 1.2 ± 0.2 × 10 −12 mol/mg protein). Enzyme activity in either direction was less during growth, correlating with a decrease in mRNA for 11β-OHSD. In cell homogenates containing 200 μM NADP(H), the enzyme functioned equally in either direction at pH 7.4 with an apparent K m for corticosterone of approximately 2 × 10 −7 M. Carbenoxolone, an inhibitor of 11β-OHSD, suppressed the dehydrogenase reaction to a greater degree than the reverse oxo-reductase reaction. Thus, in VSMC 11β-OHSD is bidirectional; under physiologic conditions intact VSMC favor the oxo-reductase reaction. Quiescent cells show greater enzyme activity than actively growing cells.

Sexual dimorphism of hepatic 11β-hydroxysteroid dehydrogenase in the rat: the role of growth hormone patterns

11 beta-Hydroxysteroid dehydrogenase (11 beta-HSD) catalyses the reversible metabolism of corticosterone to inert 11-dehydrocorticosterone. At least two isoforms exist. 11 beta-HSD-1, the first to be characterised and the only isoform for which a cDNA has been isolated, is highly expressed in liver, kidney and hippocampus. The activity of 11 beta-HSD in rat liver is higher in males, due to oestrogen repression of 11 beta-HSD-1 gene transcription in females. Sexual dimorphism in rodent liver proteins is frequently mediated indirectly via sex-specific patterns of GH release (continuous in females, pulsatile in males). We have now investigated whether this applies to 11 beta-HSD, using dwarf rats (congenitally deficient in GH) and hypophysectomised animals. 11 beta-HSD activity and 11 beta-HSD-1 mRNA expression in liver was significantly lower in control female than male rats (50% and 72% of male levels respectively). These sex differences in the liver were attenuated in dwarf rats, with both males and females showing similar levels of 11 beta-HSD activity to control males. Administration of continuous (female pattern) GH to dwarf male rats decreased hepatic 11 beta-HSD activity (30% fall) and mRNA expression (77% fall), whereas the same total daily dose of GH given in the male (pulsatile) pattern had no effect on hepatic 11 beta-HSD in female dwarf rats. Continuous GH also attenuated hepatic 11 beta-HSD activity (25% fall) and 11 beta-HSD-1 mRNA expression (82% fall) in hypophysectomised animals.(ABSTRACT TRUNCATED AT 250 WORDS)

'Liver-type' 11 beta-hydroxysteroid dehydrogenase cDNA encodes reductase but not dehydrogenase activity in intact mammalian COS-7 cells.

11 beta-Hydroxysteroid dehydrogenase (11 beta-HSD) catalyses the metabolism of corticosterone to inert 11-dehydrocorticosterone, thus preventing glucocorticoid access to otherwise non-selective renal mineralocorticoid receptors (MRs), producing aldosterone selectivity in vivo. At least two isoforms of 11 beta-HSD exist. One isoform (11 beta-HSD1) has been purified from rat liver and an encoding cDNA cloned from a rat liver library. Transfection of rat 11 beta-HSD1 cDNA into amphibian cells with a mineralocorticoid phenotype encodes 11 beta-reductase activity (activation of inert 11-dehydrocorticosterone) suggesting that 11 beta-HSD1 does not have the necessary properties to protect renal MRs from exposure to glucocorticoids. This function is likely to reside in a second 11 beta-HSD isoform. 11 beta-HSD1 is co-localized with glucocorticoid receptors (GRs) and may modulate glucocorticoid access to this receptor type. To examine the predominant direction of 11 beta-HSD1 activity in intact mammalian cells, and the possible role of 11 beta-HSD in regulating glucocorticoid access to GRs, we transfected rat 11 beta-HSD1 cDNA into a mammalian kidney-derived cell system (COS-7) which has little endogenous 11 beta-HSD activity or mRNA expression. Homogenates of COS-7 cells transfected with increasing amounts of 11 beta-HSD cDNA exhibited a dose-related increase in 11 beta-dehydrogenase activity. In contrast, intact cells did not convert corticosterone to 11-dehydrocorticosterone over 24 h, but showed a clear dose-related 11 beta-reductase activity, apparent within 4 h of addition of 11-dehydrocorticosterone to the medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of glucocorticoid in the development of glycyrrhizin-induced hypertension.

Role of alterations of corticosterone metabolism in the expression of the mineralocorticoid activity of glycyrrhizin was explored in rats. While the mineralocorticoid actions of oral glycyrrhizin were not observed in bilaterally adrenalectomized rats and dexamethasone treated rats, the mineralocorticoid actions of glycyrrhizin were fully expressed in bilaterally adrenalectomized rats supplemented with physiological doses of corticosterone. Similar mineralocorticoid actions were observed in rats given glycyrrhizin, deoxycorticosterone and pharmacological doses of corticosterone. Although increases in mean blood pressure were suppressed only by concurrent administration of spironolactone to glycyrrhizin- and deoxycorticosterone-treated rats, increases in mean blood pressure were attenuated by both the glucocorticoid antagonist RU 38486 and spironolactone in pharmacological doses of corticosterone administered rats. Pressor responses to norepinephrine and angiotensin II infusions in rats given deoxycorticosterone and pharmacological doses of corticosterone were significantly higher than in glycyrrhizin-treated rats. These results confirmed the functional significance of 11-beta-hydroxysteroid dehydrogenase in expression of the mineralocorticoid activity of glycyrrhizin.

Effects of corticosteroids on short-circuit current across the cecum of the domestic fowl, Gallus domesticus.

Both avian corticosteroid hormones, aldosterone and corticosterone, increased short-circuit current across the wall of the ceca of the domestic fowl (Gallus domesticus) in vitro. About 80% of this short-circuit current was inhibited by the Na-channel blocking drug amiloride. Corticosterone was about ten times less potent than aldosterone in increasing short-circuit current and it exerted a similar maximal effect. Cortisol (an endogenous corticosteroid hormone in mammals but not birds) was about ten times less potent than corticosterone and this difference appeared to reflect the presence of the 17 alpha-OH group in cortisol. Carbenoxolene, which inhibits 11 beta-hydroxysteroid dehydrogenase, increased the effect of corticosterone. This effect is consistent with inhibition of the metabolism of corticosterone to 11-dehydrocorticosterone. The latter was found to be about 100 times less potent than corticosterone. The effects of both aldosterone and corticosterone (also dexamethasone) were abolished by the mineralocorticoid receptor antagonist spironolactone. The results suggest that corticosterone has an effect similar to aldosterone but in vivo its action may be depressed by the activity of 11 beta-hydroxysteroid dehydrogenase. The sensitivity of the cecal preparations to corticosterone indicates that this hormone could contribute to the regulation of transcecal Na transport (absorption) in vivo.

Human Fetal Adrenal Definitive and Fetal Zone Metabolism of Pregnenolone and Corticosterone: Alternate Biosynthetic Pathways and Absence of Detectable Aldosterone Synthesis*

In the rhesus monkey and ovine fetus in utero, aldosterone concentrations do not rise in response to surgical stress, ACTH, or angiotensin-II, all of which are secretagogues for this mineralocorticoid in the adult. To assess the mechanism of this phenomenon in the human fetus, metabolism of pregnenolone and corticosterone by second trimester human fetal adrenal definitive zone and fetal zone tissue was studied. After incubation of fresh tissue with trace amounts of [3H]pregnenolone or [3H]corticosterone, the products of metabolism were separated using high performance liquid chromatography and quantified. The delta 5-3 beta-hydroxysteroids 17-hydroxypregnenolone and dehydroepiandrosterone and their sulfates comprised 85-90% of metabolized pregnenolone. In the fetal zone, cortisol was the predominant secreted delta 4-3-ketosteroid, accounting for 6-8% of the metabolized pregnenolone. In the definitive zone, progesterone and corticosterone were the predominant secreted delta 4-3-ketosteroids, each accounting for about 2% of the metabolized pregnenolone. 11-Dehydrocorticosterone and sulfates were the only metabolites detected after incubation of fetal adrenal tissue with corticosterone. 11-Dehydrocorticosterone accounted for more than 80% of the metabolized corticosterone in the definitive zone and 50% in the fetal zone. Incubations with secretagogues or antioxidants (10 nmol/L ACTH, 10 nmol/L angiotensin-II, 21 mmol/L potassium, 100 mmol/L dimethylsulfoxide, 5 mumol/L metyrapone, or 100 mumol/L butylated hydroxyanisole) did not change the pattern or extent of precursor metabolism. No aldosterone, 18-hydroxycorticosterone, or 18-hydroxydeoxycorticosterone was detected in baseline or stimulated incubations of human fetal tissue. In contrast, adult human zona glomerulosa metabolized corticosterone to aldosterone, 18-hydroxycorticosterone, and 11-dehydrocorticosterone under similar conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of carbenoxolone on glucocorticoid metabolism and Na transport in toad bladder

In humans, diminished 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) enzyme activity has been associated with sodium retention and hypertension. These studies show that the toad bladder, another target tissue epithelium displaying steroid-induced sodium transport, possesses the enzyme 11 beta-OHSD. The toad urinary bladder rapidly transformed corticosterone (3 x 10(-8) M) (50% by 10 min and 90% by 180 min) with 11-dehydrocorticosterone being the major metabolite. The 11-dehydrocorticosterone produced reached an apparent plateau when the tissue incubations were repeated with higher concentrations of corticosterone (10(-7) and 10(-6) M). Carbenoxolone sodium (2.5 x 10(-5) M), a water soluble derivative of glycyrrhetinic acid, markedly inhibited the metabolism of corticosterone (3 x 10(-8) M) to 11-dehydrocorticosterone similar to previous observations in the mammalian kidney. Carbenoxolone sodium (2.5 x 10(-5) M) did not significantly affect short-circuit current (SCC) in toad bladders when added to either the serosal or mucosal bath. However, when carbenoxolone sodium was added to the mucosal bath and 60 min later corticosterone 10(-6) M was placed in the serosal bath, bladders generated a SCC 2.07 +/- 0.17 (mean +/- SE) times above base line at 360 min compared with 1.48 +/- 0.11 in bladders exposed to corticosterone alone (P less than 0.02). In parallel experiments, carbenoxolone sodium in the mucosal bath enhanced the rise in SCC induced by cortisol 10(-6) M; 1.66 +/- 0.16 times above base line at 360 min compared with 1.07 +/- 0.14 with cortisol alone (P less than 0.02). We conclude that the toad bladder contains 11 beta-OHSD and inhibition of this enzyme with carbenoxolone sodium is associated with amplification of glucocorticoid-induced transepithelial sodium transport in this tissue. However, since the quantity of 11-dehydro-product produced appears to be limited, other factors in addition to inhibition of 11 beta-OHSD may play a role in this amplification of sodium transport.

18-Hydroxylase activity in the Y1 adrenal cell line

18-Hydroxylase activity, reported here for the first time in the mouse adrenal tumor cell line (Yl), was expressed in the metabolism of 11-deoxycorticosterone (DOC) and corticosterone (B). Detected after 24 h of incubation, it was more evident after 48 h and produced mostly 18-hydroxy-20α-DHB from these exogenous substrates. However, 18-hydroxylation was quantitatively less significant than the metabolism of 20α-reduction and 11β-hydroxylation (of DOC). The latter is also the predominant metabolism of progesterone in this cell line, during the conversion of cholesterol from the serum-supplemented culture media. The cytochrome P-450 11β activity of the Yl cells is similar to that of the mouse in vivo which catalyzes the production of an 11β,18-dihydroxylated metabolite as the principal 18-hydroxylated steroid. It is different from that of other species, such as the rat and the bovine, both in terms of the ratio of 11β- to 18-hydroxylated metabolites and of the structure of these metabolites.

Mineralocorticoid specificity of renal type I receptors: Binding and metabolism of corticosterone

In cytosol preparations renal mineralocorticoid receptors have equivalent affinity for aldosterone and corticosterone; in vivo, such receptors are clearly aldosterone-selective. To explore this difference, we have compared the binding of both steroids in kidney slices, high speed supernatants and true cytosols in vitro, in the presence of RU28362 to exclude steroids from Type II glucocorticoid receptors, and/or in the presence of cortisol 17β-COOH to exclude corticosterone from transcortin. In addition, we have explored the effect of tissue preparation and cortisol 17β-COOH on the level of activity of the renal enzyme 11β-OH steroid dehydrogenase. The results of the present studies support the hypothesis that the predominant aldosterone specific-conferring mechanism for renal Type I receptors in vivo in the enzyme 11β-OH steroid dehydrogenase, and underline the potential difficulties in interpreting studies which include multiple potential ligands to multiple potential binding sites.

The metabolic clearance rate of corticosterone in lean and obese male Zucker rats

The obese Zucker rat is an animal model of human juvenile-onset obesity. There rats exhibit numerous endocrine and metabolic abnormalities. Adrenalectomy of obese rats has been shown to reduce or reverse several of these abnormalities, thereby implying that corticosterone may contribute to the expression of obesity in this animal. Furthermore, it has been shown that the circadian rhythm of plasma corticosterone is disturbed in obese Zucker rats resulting in elevated morning plasma corticosterone concentrations in obese rats as compared to lean rats. In a effort to better elucidate the mechanism of the elevated morning levels of plasma corticosterone, the metabolic clearance rate of corticosterone was determined in the morning for lean and obese male Zucker rats (12 to 20 weeks). Additionally, the biliary and urinary excretion of labeled corticosterone and/or its metabolites were determined. The metabolic clearance rate of corticosterone was significantly greater in obese rats than in their lean counterparts. Both the metabolic clearance rate and the volume of compartments significantly correlated with body weight. No correlation was found between body weight and the elimination rate constant. The increased metabolic clearance rate of obese rats appeared to be due to an increase in the physiologic distribution of corticosterone and not to an alteration in the enzymes responsible for corticosterone metabolism. It appears that the metabolic clearance rate of corticosterone in obese Zucker rats does not contribute to elevated morning concentrations of plasma corticosterone previously observed in these animals. It suggests that the adrenal corticosterone secretion rate must actually be greater than one would expect from the plasma corticosterone concentrations alone.

Renal epithelial cell lines (BSC-1, MDCK, LLC-PK 1) express 11β-hydroxysteroid dehydrogenase activity

Renal tissue of several species has been shown to express considerable 11β-hydroxysteroid dehydrogenase (11-HSD, EC 1.1.1.146) activity. However, it is uncertain as to which renal cell types exhibit 11-HSD activity. In the present study, we investigated corticosterone metabolism in BSC-1 cells, a continuous renal epithelial cell line derived from the African green monkey ( Cercopithecus aethiops). In incubation experiments using 3H-labelled corticosterone and HPLC, we have demonstrated oxidative 11-HSD activity in intact monolayers of BSC-1 cells as well as in BSC-1 cell homogenates. 11-HSD activity in cell homogenates could be stimulated 7–9-fold by the addition of exogenous NADP + (1 mM). In contrast, no reductive 11-HSD could be detected either in intact cells or in cell homogenates under various experimental conditions which were designed to favor reductive 11-HSD activity. Pilot experiments were performed in cell homogenates from two other renal epithelial cell lines derived from canine (MDCK) and porcine (LLC-PK 1) kidney. They also revealed oxidative but no reductive 11-HSD activity. The data provide evidence for an epithelial localization of renal oxidative 11-HSD activity.

Steps of glucocorticoid action in normal and diabetic rat placenta

This investigation examined the effects of Streptozotocm diabetes in pregnancy on several parameters of glucocorticoid action in the rat placenta. Pregnant diabetic rats showed reduced body weight, increased adrenal weight and serum corticosterone concentrations. Glucocorticoid receptors in placental cytosol of labyrinthine zone, measured in the absence of MoO 4Na 2 were similar in control and diabetic rats, but after addition of MoO 4Na 2 receptor number were moderately, but significantly reduced m diabetic placentas ( P < 0.01). No changes in affinity were detected in saturation analysis. Furthermore, transformation of the receptor assessed by its capacity for binding to DNA-cellulose, was enhanced in diabetic animals, suggesting increased efficiency of the receptor-bound hormone. Since the function of the glucocorticoid receptor of rat placenta may be the inhibition of local progesterone production (Heller and De Nicola, J. steroid Biochem. 19 (1983) 1339–1343), we determined progesterone synthesis in vitro and found that diabetic placentas synthesized significantly less progesterone than control tissue ( P < 0.05). Lastly, we found that the metabolism of corticosterone to 11-dehydrocorticosterone, while declining in control placentas as pregnancy advanced, it was sustained in diabetic pregnancy. It is suggested that diabetic rat placentas showed increased activity towards the glucocorticoid receptor, resulting in reduction in progesterone synthesis and sstained catabolism of corticosterone. The latter may possibly constitute a compensatory mechanism to protect the fetal compartment from high levels of maternal glucocorticoids.

Effects of chronic administration of benfluorex to rats on the metabolism of corticosterone, glucose, triacylglycerols, glycerol and fatty acid

(1) Rats were fed on diets enriched with sucrose, beef tallow or corn oil and treated for 11–16 days with 50 mg of benfluorex per kg of body weight. By these times the growth rate and food intake were not significantly different from those of control rats. (2) Benfluorex approximately halved the concentration of circulating triacylglycerol in rats fed the beef tallow or sucrose diets. (3) It did not significantly alter the total lipoprotein lipase activity in diaphragm, heart and adipose tissue. (4) The clearance of triacylglycerols from chylomicrons exhibited two t 1 2 values of about 0.6 and 6.9 min in rats fed the beef tallow diet. Benfluorex did not significantly alter these values. (5) Benfluorex did not significantly alter the rate of appearance of triacylglycerol in the blood of rats injected with Triton WR 1339 to block triacylglycerol uptake. It did, however, decrease the rise in circulating glucose which presumably resulted from the stress of the procedure. (6) Benfluorex decreased the extent and duration of the rise in serum corticosterone when rats maintained on the corn oil diet were fed acutely with fructose. It also decreased the circulating concentrations of glycerol, triacylglycerol and glucose after fructose feeding. (7) Rats fed on the corn oil diet and then treated with benfluorex had lower concentrations of circulating glucose, triacylglycerol, glycerol and fatty acids after being injected with 2-deoxyglucose. (8) It is proposed that some of the long-term hypoglycaemic and hypotriglyceridaemic effects of benfluorex could be mediated indirectly through changes in endocrine balance, perhaps via the serotonergic system and in particular, by decreasing the effects of stress hormones relative to insulin. The implications of these findings are discussed in relation to controlling metabolism in stress conditions and for the management of obesity, diabetes and atherosclerosis.

HPLC separation of corticosterone metabolites and its use in following corticosterone metabolism and transport in the isolated rat hepatocyte

Incubating isolated rat hepatocytes with tritium labelled and unlabelled corticosterone at 37°C resulted in the rapid appearance of at least nine corticosterone metabolites. A quick, relatively easy, and quantitative high performance liquid Chromatographic (HPLC) method was used to separate these metabolites and follow their rate of appearance both intra- and extracellulariy. We found different intraand extracellular amounts of each metabolite at a particular time and this suggested that some metabolites were more available for transport than others.

Effects of Newcastle disease virus administration to mice on the metabolism of cerebral biogenic amines, plasma corticosterone, and lymphocyte proliferation

Newcastle disease virus (NDV) administration to mice increased concentrations of plasma corticosterone, with a maximal effect at 8 h. This elevation of plasma corticosterone concentrations was not observed in hypophysectomized animals in which the completeness of the hypophysectomy was verified by functional tests. NDV administration consistently increased concentrations of free tryptophan in all brain regions examined (prefrontal cortex, hypothalamus, and brain stem). It also caused an activation of cerebral catecholamine and indoleamine metabolism as determined by measurement of the amines and their catabolites. 3-Methoxy,4-hydroxyphenylethyleneglycol (MHPG), the major catabolite of norepinephrine (NE), homovanillic acid (HVA), a major catabolite of dopamine (DA), and 5-hydroxyindoleacetic acid (5-HIAA), the major catabolite of serotonin (5-HT), were all increased in both hypothalamus and brain stem. Ratios of catabolites to the parent amine, considered to be an index of utilization of the neurotransmitters, were increased for NE, DA, and 5-HT in the hypothalamus and for DA and 5-HT in the brain stem. This pattern of changes resembles that observed following stressors such as footshock or restraint. There were also significant increases of tryptophan, HVA, dihydroxyphenylacetic acid (DOPAC), and 5-HIAA in hypophysectomized relative to sham-operated mice. The NDV treatment also increased thymus weights and markedly decreased the proliferative responses of isolated spleen cells to phytohemagglutinin, concanavalin A, pokeweed mitogen, and Escherichia coli lipopolysaccharide. These changes were not caused by increased circulating corticosterone because they were present at equal magnitude in hypophysectomized mice. Thymosin α 1 concentrations in the plasma were not altered by NDV or hypophysectomy. These results indicate that administration of NDV to mice can initiate neurochemical and endocrine responses like those observed during stress and can also cause immunosuppression. They are thus consistent with the hypothesis that a virus can be a stressor.

Effect of soman (pinacolyl methylphosphonofluoridate) on the blood levels of corticosterone and adrenocorticotropin in mice.

Mice were poisoned by an extremely toxic organophosphate anticholinesterase soman (pinacolyl methylphosphonofluoridate), 50 or 100 micrograms/kg at 1000, and the serum concentrations of corticosterone were determined fluorometrically at 3-h intervals for at least 24 h. The lower soman dose (50 micrograms/kg) produced a modest increase in serum corticosterone concentrations but by 24 h the levels were not significantly different from control. Following the higher soman dose (100 micrograms/kg) the serum corticosterone levels were elevated significantly (p less than 0.05), for at least 27 h. However, ACTH concentrations were not elevated. It is possible that the elevated levels of corticosterone were due to a reduced metabolism and excretion of corticosterone resulting from the intense hypothermia, following soman poisoning which may change cardiac output and organ (liver and kidney) perfusion and not due to an enhanced release from the adrenal gland.