scholarly journals Glucocorticoids, thyroid hormones, and iodothyronine deiodinases in embryonic saltwater crocodiles

2002 ◽  
Vol 283 (5) ◽  
pp. R1155-R1163 ◽  
Author(s):  
Caroline A. Shepherdley ◽  
Christopher B. Daniels ◽  
Sandra Orgeig ◽  
Samantha J. Richardson ◽  
Barbara K. Evans ◽  
...  
Keyword(s):  
Thyroid Hormones ◽  
Plasma Concentrations ◽  
Liver Microsomes ◽  
Free Thyroid Hormones ◽  
Iodothyronine Deiodinases ◽  
High K ◽  
Liver And Kidney ◽  
Crocodylus Porosus ◽  
Kidney Microsomes ◽  
The Relationship

We investigated the relationship between glucocorticoids, thyroid hormones, and outer ring and inner ring deiodinases (ORD and IRD) during embryonic development in the saltwater crocodile ( Crocodylus porosus). We treated the embryos with the synthetic glucocorticoid dexamethasone (Dex), 3,3′,5-triiodothyronine (T3), and a combination of these two hormones (Dex + T3). The effects of these treatments were specific in different tissues and at different stages of development and also brought about changes in plasma concentrations of free thyroid hormones and corticosterone. Administration of Dex to crocodile eggs resulted in a decrease in 3,3′,5,5′-tetraiodothyronine (T4) ORD activities in liver and kidney microsomes, and a decrease in the high- K m rT3 ORD activity in kidney microsomes, on day 60 of incubation. Dex treatment increased the T4 ORD activity in liver microsomes, but not kidney microsomes, on day 75 of incubation. Dex administration decreased T3 IRD activity in liver microsomes. However, this decrease did not change plasma-free T3 concentrations, which suggests that free thyroid hormone levels are likely to be tightly regulated during development.

Evidence for isoforms of 11β-hydroxysteroid dehydrogenase in the liver and kidney of the guinea pig

1997 ◽  
Vol 153 (2) ◽  
pp. 291-298 ◽  
Author(s):  
M Quinkler ◽  
B Kosmale ◽  
V Bähr ◽  
W Oelkers ◽  
S Diederich
Keyword(s):  
Guinea Pig ◽  
Liver Enzyme ◽  
Liver Microsomes ◽  
Hydroxysteroid Dehydrogenase ◽  
Type I ◽  
Fixed Concentration ◽  
Kidney Enzyme ◽  
Liver And Kidney ◽  
Kidney Microsomes ◽  
Kidney Liver

Abstract In the human and in rodents like the rat and mouse, the liver enzyme 11β-hydroxysteroid dehydrogenase type I (11β-HSD-I) is a functional oxidoreductase preferring NADP+/NADPH as cosubstrate, while the renal isoenzyme (11β-HSD-II) prefers NAD+ as cosubstrate, and seems to be a pure oxidase and protects the tubular mineralocorticoid (MC) receptor from occupancy by cortisol and corticosterone. We studied the enzyme kinetics of 11β-HSDs in kidney and liver microsomes of the guinea pig, a species whose zoological classification is still a matter of debate. With a fixed concentration of 10−6 mol/l cortisol, liver and kidney microsomes preferred NAD+ to NADP+ (10−3 mol/l) for the conversion to cortisone. Kidney microsomes converted cortisol to cortisone with Km values of 0·64 μmol/l and 9·8 μmol/l with NAD+ and NADP+ as cosubstrates respectively. The reduction of cortisone to cortisol was slow with kidney microsomes, but could be markedly enhanced by adding an NADH/NADPH regenerating system: with NADPH as preferred cosubstrate, the approximate Km was 7·2 μmol/l. This indicated the existence of both isoenzymes in the guinea pig kidney. Liver microsomes oxidized cortisol to cortisone with similar Km and Vmax values for NAD+ to NADP+ as cosubstrates (Km of 4·3 μmol/l and 5·0 μmol/l respectively). The NAD+ preference for the oxidation of 10−6 mol/l cortisol described above may be due to a second, NAD+-preferring 11β-HSD with a Km of 1·4 μmol/l. In contrast to the kidney, liver microsomes actively converted cortisone to cortisol with a preference for NADPH (Km: 1·2 μmol/l; Vmax: 467 nmol/min per mg protein). Thus, the main liver enzyme is similar to the oxidoreductase of other species (11β-HSD-I) and is also present in the kidney, while the main kidney enzyme is clearly NAD+-preferring. This kidney enzyme (analogous to 11β-HSD-II of other species) seems to be suitable for the protection of the MC receptor from the high free plasma cortisol levels of the guinea pig. Journal of Endocrinology (1997) 153, 291–298

Progesterone C21 hydroxylation and steroid carboxylic acid biosynthesis in the rabbit. In vitro studies with endocrine, metabolic, and potential target tissues

1983 ◽  
Vol 61 (7) ◽  
pp. 722-730 ◽  
Author(s):  
I. R. Senciall ◽  
G. Bullock ◽  
S. Rahal
Keyword(s):  
Cytochrome C ◽  
Liver Microsomes ◽  
Acid Synthesis ◽  
Rabbit Kidney ◽  
Liver And Kidney ◽  
Kidney Microsomes ◽  
Intraspecies Variability ◽  
First Time ◽  
Cytochrome P 450

Progesterone C21-hydroxylase activity has been demonstrated with rabbit kidney microsomes for the first time and the formation of 21-hydroxy-4-pregnen-3,20-dione (DOC) by rabbit liver and kidney microsomes has been quantitated. Considerable intraspecies variability in enzyme activity occurred with both tissues. The liver enzyme (Vmax = 1.28–38.0 nmol/mg protein per 30 min of incubation) was significantly more active than the kidney enzyme (Vmax = 0.028–0.28 nmol/mg protein per 30 min of incubation). Apparent KM values were 1.39 and 0.8 μM, respectively. Cytochrome c (10−5 M), potassium ferricyanide (10−3 M), and 2-methyl-1,2-di-3-pyridyl-1-propanone (metyrapone; 10−3 M) were strongly inhibitory with both tissues, whereas the liver microsomal system was less sensitive than the kidney to CO–air (90:10 v/v) inhibition. Metabolism of [14C]DOC to 4-pregnen-3,20-dione-21-oic (pregnenoic) and 4-androsten-3-one-17β-carboxylic (etienic) acids by liver microsomes and adrenal and ovary homogenates was differentially affected by several factors. CO–air (90:10 v/v), cytochrome c (10−5 M), and metyrapone (10−3 M) inhibited pregnenoic acid synthesis to a greater extent than etienic acid. Sodium cyanide had a stimulatory effect on the synthesis of pregnenoic acid by the liver but less consistent effects with other tissues. These results suggest that one or more cytochrome P-450 systems may be involved in the oxidation of progesterone through to pregnenoic acid by rabbit tissues.

Transient Prealbumin- Associated Hyperthyroxinemia in TSH-Producing Pituitary Adenoma

1990 ◽  
Vol 29 (01) ◽  
pp. 40-43 ◽  
Author(s):  
W. Langsteger ◽  
P. Költringer ◽  
P. Wakonig ◽  
B. Eber ◽  
M. Mokry ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Case Report ◽  
Pituitary Adenoma ◽  
Thyroid Hormones ◽  
Protein Binding ◽  
Alpha Subunit ◽  
Normal Range ◽  
Thyroxine Binding Globulin ◽  
Free Thyroid Hormones ◽  
Transmission Computed Tomography

This case report describes a 38-year-old male who was hospitalized for further clarification of clinically mild hyperthyroidism. His increased total hormone levels, the elevated free thyroid hormones and the elevated basal TSH with blunted response to TRH strongly suggested a pituitary adenoma with inappropriate TSH incretion. Transmission computed tomography showed an intrasellar expansion, 16 mm in diameter. The neoplastic TSH production was confirmed by an elevated alpha-subunit and a raised molar alpha-sub/ATSH ratio. However, T4 distribution on prealbumin (PA, TTR), albumin (A) and thyroxine binding globulin (TBG) showed a clearly increased binding to PA (39%), indicating additional prealbumin-associated hyperthyroxinemia. The absolute values of PA, A and TBG were within the normal range. After removal of the TSH-producing adenoma, basal TSH, the free thyroid hormones and T4 binding to prealbumin returned to normal. Therefore, the prealbumin-associated hyperthyroxinemia had to be interpreted as a transitory phenomenon related to secondary hyperthyroidism (T4 shift from thyroxine binding globulin to prealbumin) rather than a genetically conditioned anomaly of protein binding.

scholarly journals Stimulation of mitochondrial calcium ion efflux by thiol-specific reagents and by thyroxine. The relationship to adenosine diphosphate retention and to mitochondrial permeability

1979 ◽  
Vol 182 (2) ◽  
pp. 455-464 ◽  
Author(s):  
E J Harris ◽  
M Al-Shaikhaly ◽  
H Baum
Keyword(s):  
Thyroid Hormones ◽  
Calcium Ion ◽  
Adenine Nucleotides ◽  
Adenosine Diphosphate ◽  
Ruthenium Red ◽  
Reduced Form ◽  
Factors Affecting ◽  
Ph Values ◽  
Rat Heart Mitochondria ◽  
The Relationship

Respiring rat heart mitochondria were loaded with Ca2+ and then treated with Ruthenium Red. The factors affecting the subsequent Ca2+-efflux were studied. Addition of rotenone or antimycin led to a decline of efflux except at pH values above 7.2, provided the load was less than about 80 nmol per mg of protein. Oligomycin reversed the effect of the respiratory inhibitors. Independently of respiration, efflux was stimulated by the uncoupler trifluoromethyltetrachlorbenzimadazole, by mersalyl and by thyroid hormones. The stimulated efflux could be diminished by ADP, with Mg2+ as cofactor if efflux was rapid. With respiration in progress, efflux could be stimulated by N-ethylmaleimide and 5,5′-dithiobis-(2-nitrobenzoate). The effects of mersalyl and of thyroid hormones could be diminished with dithiothreitol. In the absence of stimulating agents, the Ca2+ efflux was proportional to the load up to some critical amount, this critical amount was decreased by the agents. Thyroxine and mersalyl caused not only loss of Ca2+, but also simultaneous, but not necessarily proportional, loss of internal adenine nucleotides. Both efflux rates were kept at a low value by bongkrekic acid added before the stimulating agent. It is concluded that Ca2+ efflux is a measure of a permeability controlled by the binding of ADP (an Mg2+) to the inner membrane, and that this in turn depends on the maintenance of certain thiol gropus in a reduced form by a reaction that uses NADH and ATP and the energy-linked transhydrogenase.

Differential hormonal regulation of carbonyl reductase activities in liver and kidney microsomes of rat

Xenobiotica ◽  
2002 ◽  
Vol 32 (9) ◽  
pp. 729-737 ◽  
Author(s):  
Y. Imamura ◽  
H. Takada ◽  
R. Kamizono ◽  
M. Otagiri
Keyword(s):  
Hormonal Regulation ◽  
Carbonyl Reductase ◽  
Liver And Kidney ◽  
Kidney Microsomes

scholarly journals The relationship between perchlorate in drinking water and cord blood thyroid hormones: First experience from Iran

2015 ◽  
Vol 6 (1) ◽  
pp. 17
Author(s):  
Parinaz Poursafa ◽  
Ashraf Javidi ◽  
Nasim Rafiei ◽  
MohammadMehdi Amin ◽  
Silva Hovsepian ◽  
...  
Keyword(s):  
Drinking Water ◽  
Thyroid Hormones ◽  
Cord Blood ◽  
The Relationship

scholarly journals In vitro and in vivo evaluation of hypothermia on pharmacokinetics and pharmacodynamics of nimodipine in rabbits

2017 ◽  
Vol 46 (1) ◽  
pp. 335-347 ◽  
Author(s):  
Yu-xing Fei ◽  
Tian-hong Zhang ◽  
Jing Zhao ◽  
He Ren ◽  
Ya-nan Du ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Protein Binding ◽  
Plasma Concentrations ◽  
Liver Microsomes ◽  
Intrinsic Clearance ◽  
Pharmacokinetics And Pharmacodynamics ◽  
In Vivo Evaluation

Objective To investigate the effect of hypothermia on the pharmacokinetics and pharmacodynamics of nimodipine in rabbits using in vivo and in vitro methods. Methods Five healthy New Zealand rabbits received a single dose of nimodipine (0.5 mg/kg) intravenously under normothermic and hypothermic conditions. Doppler ultrasound was used to monitor cerebral blood flow, vascular resistance, and heart rate. In vitro evaluations of protein binding, hepatocyte uptake and intrinsic clearance of liver microsomes at different temperatures were also conducted. Results Plasma concentrations of nimodipine were significantly higher in hypothermia than in normothermia. Nimodipine improved cerebral blood flow under both conditions, but had a longer effective duration during the hypothermic period. Low temperature decreased the intrinsic clearance of liver microsomes, with no change in protein binding or hepatocyte uptake of nimodipine. Conclusion Nimodipine is eliminated at a slower rate during hypothermia than during normothermia, mainly due to the decreased activity of cytochrome P450 enzymes. This results in elevated system exposure with little enhancement in pharmacological effect.

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