RESPIRATORY AND ENZYMIC CHANGES IN RESPONSE TO STEROID HORMONES

1970 ◽  
Vol 47 (2) ◽  
pp. 159-166 ◽  
Author(s):  
T. DALTON ◽  
R. S. SNART
Keyword(s):  
Rat Liver ◽  
Enzymic Activity ◽  
Toad Bladder ◽  
Target Tissue ◽  
Transaminase Activity ◽  
Bladder Tissue ◽  
Cellular Processes ◽  
Receptor Sites ◽  
Common Effect ◽  
Stimulation Of

SUMMARY Changes in respiration and enzymic activity were measured in toad bladder tissue and homogenates in response to aldosterone and in rat liver tissue and homogenates in response to corticosterone. The results showed that the stimulation of target tissue may be associated with the saturation of two types of receptor sites for these hormones. The mechanism of action of both hormones is discussed in terms of a common effect on the control of respiration of the target tissue, and a second effect on the control of cellular processes such as the entry of sodium into the epithelial cells of toad bladder or increased transaminase activity in rat liver.

scholarly journals A kinetic study of the soluble 5′-nucleotidase of rat liver

1977 ◽  
Vol 162 (3) ◽  
pp. 611-616 ◽  
Author(s):  
G van den Berghe ◽  
C van Pottelsberghe ◽  
H G Hers
Keyword(s):  
Uric Acid ◽  
Rat Liver ◽  
Liver Cell ◽  
Adenine Nucleotides ◽  
Enzymic Activity ◽  
Kinetic Properties ◽  
Stimulatory Action ◽  
Physiological Conditions ◽  
Hydrolysis Of ◽  
Stimulation Of

1. The kinetic properties of the 5′-nucleotidase (EC 3.1.3.5) present in the cytosol of rat liver were investigated in relation to the conversion of adenine nucleotides into uric acid, with particular reference to the stimulation of this process by fructose. The enzyme was assayed by the release of Pi and by a new and more sensitive radiochemical procedure. 2. When IMP was used as substrate, the partially purified enzyme displayed almost hyperbolic kinetics (h = 1.1) with S0.5 = 1.2 mM. Similar kinetics were observed with GMP and other nucleoside 5′-monophosphates, except AMP. 3. Vmax. of the enzyme for AMP was about the same as for IMP, but the kinetics were sigmoidal (h = 1.6) with S 0.5 = 10 mM. 4. The hydrolysis of IMP was inhibited competitively by GMP. IMP, at concentrations up to 0.5 mM, had a paradoxical stimulatory action on the hydrolysis of 2-5 mM-AMP and was inhibitory at higher concentrations. 5. The activity of the enzyme towards AMP and IMP was stimulated by ATP and GTP, and inhibited by Pi. Activators and inhibitor approximately cancelled each others' effects. At pH 7.4, the enzymic activity with 0.2 mM-AMP was undetectable under physiological conditions. 6. It is concluded that, in the liver cell, AMP is not hydrolysed by the soluble 5′-nucleotidase, but that its degradation requires prior deamination to IMP.

scholarly journals The effect of aflatoxin B1 on normal and cortisol-stimulated rat liver ribonucleic acid synthesis

1972 ◽  
Vol 130 (2) ◽  
pp. 619-629 ◽  
Author(s):  
G. E. Neal
Keyword(s):  
Rna Polymerase ◽  
Rat Liver ◽  
Aflatoxin B1 ◽  
Polymerase Activity ◽  
Enzymic Activity ◽  
Target Area ◽  
Receptor Sites ◽  
Rna Polymerase Activity

1. Aflatoxin B1, administered in vivo, inhibits the incorporation of [14C]orotic acid in vivo into rat liver nuclei, and also inhibits both Mg2+- and Mn2+-dependent RNA polymerase activities in nuclei assayed in vitro. 2. Aflatoxin B1 inhibits the cortisol-induced increase in incorporation of [14C]leucine in vivo, but does not affect the control value of this activity. 3. Aflatoxin B1 administered in vivo inhibits the increase in nuclear Mg2+-dependent RNA polymerase activity, assayed in vitro, which results from the treatment with cortisol. 4. Adrenalectomy causes a decrease in Mg2+-dependent RNA polymerase activity. The effect on this enzymic activity of adrenalectomy plus treatment with aflatoxin B1 is no greater than that of treatment with aflatoxin B1 alone. 5. These results suggest that the inhibition of cortisol-stimulated biochemical pathways by aflatoxin B1 is due to an inhibition of cortisol-stimulated RNA synthesis. 6. The cytoplasmic action of aflatoxin is thought to be due to a competition for receptor sites on the endoplasmic reticulum between steroid hormones and aflatoxin B1. No evidence was obtained for a similar competition for nuclear receptor sites between [3H]cortisol and aflatoxin B1. 7. No differences were observed between the activities of RNA polymerase preparations solubilized from control or aflatoxin-inhibited nuclei. 8. No differences in ‘melting’ profiles were observed between DNA and chromatin preparations isolated from control nuclei or from aflatoxin-inhibited nuclei. 9. It is suggested that aflatoxin B1 exerts its effect on RNA polymerase by decreasing the template capacity of the chromatin and that the aflatoxin ‘target’ area of the chromatin includes that region which is stimulated by cortisol. This process, however, does not involve inhibiting the movement of cortisol from the outside of the hepatic cell to the nuclear chromatin.

Effects of 5-5'-Diphenyl-2-thiohydantoin (DPTH) and Thyroxine on the Ultrastructure and Chemical Composition of Rat Liver

1971 ◽  
Vol 29 ◽  
pp. 570-571
Author(s):  
E. A. Elfont ◽  
R. B. Tobin ◽  
D. G. Colton ◽  
M. A. Mehlman
Keyword(s):  
Chemical Composition ◽  
Rat Liver ◽  
Future Study ◽  
Mode Of Action ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Effective Inhibitor ◽  
Biochemical Effects ◽  
Glycerophosphate Dehydrogenase ◽  
Stimulation Of

Summary5,-5'-diphenyl-2-thiohydantoin (DPTH) is an effective inhibitor of thyroxine (T4) stimulation of α-glycerophosphate dehydrogenase in rat liver mitochondria. Because this finding indicated a possible tool for future study of the mode of action of thyroxine, the ultrastructural and biochemical effects of DPTH and/or thyroxine on rat liver mere investigated.Rats were fed either standard or DPTH (0.06%) diet for 30 days before T4 (250 ug/kg/day) was injected. Injection of T4 occurred daily for 10 days prior to sacrifice. After removal of the liver and kidneys, part of the tissue was frozen at -50°C for later biocheailcal analyses, while the rest was prefixed in buffered 3.5X glutaraldehyde (390 mOs) and post-fixed in buffered 1Z OsO4 (376 mOs). Tissues were embedded in Araldlte 502 and the sections examined in a Zeiss EM 9S.Hepatocytes from hyperthyroid rats (Fig. 2) demonstrated enlarged and more numerous mitochondria than those of controls (Fig. 1). Glycogen was almost totally absent from the cytoplasm of the T4-treated rats.

Activation of Hageman Factor by α-Adrenergic Stimulation

1970 ◽  
Vol 23 (03) ◽  
pp. 417-422 ◽  
Author(s):  
D. G McKay ◽  
J.-G Latour ◽  
Mary H. Parrish
Keyword(s):  
Disseminated Intravascular Coagulation ◽  
Adrenergic Receptor ◽  
Adrenergic Stimulation ◽  
Hageman Factor ◽  
Intravascular Coagulation ◽  
Receptor Sites ◽  
High Doses ◽  
Stimulation Of

SummaryThe infusion of epinephrine in high doses produces disseminated intravascular coagulation by activation of Hageman factor. The effect is blocked by phenoxybenz-amine and is therefore due to stimulation of α-adrenergic receptor sites.

The Effect of Oral Ethanol on Glutamic Pyruvic and Glutamic Oxalacetic Transaminase Activity in the Rat Liver

1958 ◽  
Vol 19 (1) ◽  
pp. 54-68 ◽  
Author(s):  
Keith S. Henley ◽  
Hugh S. Wiggins ◽  
Basil I. Hirschowitz ◽  
H. Marvin Pollard
Keyword(s):  
Rat Liver ◽  
Transaminase Activity ◽  
Glutamic Oxalacetic Transaminase
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