scholarly journals Influence of glucagon, 6-N,2′-O-dibutyryladenosine 3′:5′-cyclic monophosphate and triamcinolone on the arginine synthetase system in perinatal rat liver

1972 ◽  
Vol 126 (1) ◽  
pp. 89-98 ◽  
Author(s):  
A L. Schwartz
Keyword(s):  
Cyclic Amp ◽  
Rat Liver ◽  
Cyclic Nucleotide ◽  
Time Course ◽  
Fold Increase ◽  
Dibutyryl Cyclic Amp ◽  
System Activity ◽  
Cyclic Monophosphate ◽  
Foetal Rat ◽  
Postnatal Rats

1. The administration of triamcinolone (19–190μg/animal) to postnatal rats increased the arginine synthetase system activity 1.2–2.5-fold above control values 24h after exposure to the hormone. Cortisol (hydrocortisone), however, increased the arginine synthetase system activity only when larger (190μg/animal) or repeated daily doses were given. Glucagon (100μg/animal) stimulated arginine synthetase system activity only after the second postnatal day. None of these agents increased the activity in 19.5–21.5-day foetuses after intrauterine administration. 2. The viability of foetal rat liver explants maintained in organ culture for up to 54h was validated both by ultramicroscopic examination and by incorporation of radioactive leucine and orotic acid. 3. In organ cultures of foetal rat liver explants (18.5 days to term), triamcinolone (20μg/ml of medium) evoked a 2.8–4.3-fold increase after 24h of incubation. This increase was completely inhibited by actinomycin D (25μg/ml) or cycloheximide (10μg/ml). Cortisol (5–50μg/ml) or glucagon (0.067–67μg/ml) also increased the arginine synthetase system activity above the respective control values, but there was no increase in activity with insulin (0.05–0.25i.u./ml). 4. Maximum concentrations of glucagon (67μg/ml), dibutyryl cyclic AMP (6-N,2′-O-dibutyryladenosine 3′:5′-cyclic monophosphate) (0.1mm) and triamcinolone (20μg/ml) incubated for 24h with foetal rat liver explants each produced between a two-and three-fold increase in the activity of the arginine synthetase system. Combinations of maximum amounts of glucagon and the cyclic nucleotide did not produce a greater effect than either agent alone. However, the combination of dibutyryl cyclic AMP with triamcinolone appeared to produce somewhat less than additive effects. 5. The effects of the cyclic nucleotide and triamcinolone were evident after 12h of incubation and increased steadily throughout the 24h of observation. This time-course of increased enzyme activity is very much slower than that reported for the induction of other enzymes in explant cultures of foetal rat liver.

scholarly journals Stimulation by 6-N,2′-O-dibutyryladenosine 3′:5′-cyclic monophosphate and glucocorticoids of phosphoenolpyruvate carboxykinase in the isolated perfused rat liver (Short Communication)

1974 ◽  
Vol 142 (3) ◽  
pp. 691-693 ◽  
Author(s):  
Wieland B. Huttner ◽  
Wilhelm Krone ◽  
Hans J. Seitz ◽  
Wolfgang Tarnowski
Keyword(s):  
Cyclic Amp ◽  
Cyclic Nucleotide ◽  
Time Course ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Direct Action ◽  
Isolated Perfused Rat Liver ◽  
Dibutyryl Cyclic Amp ◽  
Low Protein ◽  
Additive Increase

Dibutyryl cyclic AMP stimulated the activity of phosphoenolpyruvate carboxykinase in perfused livers of rats, fed on a low-protein diet, linearly over a 6h period. The enzyme activity was also significantly elevated by dexamethasone, the effect being considerably lower than that of the cyclic nucleotide. Since the time-course of phosphoenolpyruvate carboxykinase activity in response to dibutyryl cyclic AMP resembled that observed after dibutyryl cyclic AMP injection into intact animals, it is suggested that induction of the enzyme in vivo is due to a direct action of the cyclic nucleotide on the liver. Combined administration of dibutyryl cyclic AMP and glucocorticoids did not lead to an additive increase of liver phosphoenolpyruvate carboxykinase activity, either in vivo or in the perfused organ.

scholarly journals Dibutyryladenosine 3′:5′-cyclic monophosphate-mediated changes in rat cells involve macromolecular alterations in vinblastine-precipitable proteins

1978 ◽  
Vol 174 (3) ◽  
pp. 1071-1074
Author(s):  
A T Meza ◽  
M Rieber
Keyword(s):  
Molecular Weight ◽  
Cyclic Amp ◽  
Cell Cultures ◽  
Cyclic Nucleotide ◽  
Dibutyryl Cyclic Amp ◽  
Cyclic Monophosphate ◽  
Three Components

ts-NT3-KR rat cell cultures show the loss of three components in the molecular-weight region 200,000–250,000 when exposed to dibutyryl cyclic AMP, under conditions of both restriction and expression of the transformed phenotype. Vinblastine is able to precipitate preferentially from control cultures the species that are decreased by exposure to the cyclic nucleotide. Serum-starved cultures exposed to dibutyryl cyclic AMP reveal differences in their vinblastine precipitates, depending on whether the expression of the transformation phenotype is restricted or not.

scholarly journals Changes in the activities of the enzymes of urea synthesis caused by dexamethasone and dibutyryladenosine 3′:5′-cyclic monophosphate in foetal rat liver maintained in organ culture

1976 ◽  
Vol 160 (2) ◽  
pp. 159-162 ◽  
Author(s):  
E Edkins ◽  
N C R Rïhä
Keyword(s):  
Cyclic Amp ◽  
Organ Culture ◽  
Rat Liver ◽  
Urea Cycle ◽  
Defined Medium ◽  
Urea Synthesis ◽  
Dibutyryl Cyclic Amp ◽  
Carbamoyl Phosphate ◽  
Foetal Rat ◽  
Ornithine Transcarbamoylase

Liver explants from 19-day foetal rats were maintained in organ culture, in a defined medium, for up to 48h. Both 6-N,2′-O-dibutyryl cyclic AMP, in the presence of theophylline, and dexamethasone caused an increase in the activities of carbamoyl phosphate synthase, argininosuccinate synthetase, argininosuccinate lyase and arginase. These increases could be abolished by simultaneously incubating the explants with cycloheximide. No change in the activity of ornithine transcarbamoylase was found with either hormone. Previous work has shown that injection of corticosteroids into 19.5-day foetal rats in utero did not cause an increase in the arginine synthetase system. Present results suggest that this lack of effect is not due to any incompetence of the foetal rat liver at this stage to respond to this agent. The observations on ornithine transcarbamoylase activity suggest that this enzyme is induced in the liver of the perinatal rat by neither corticosteroids nor hormones acting via cyclic AMP, and it may be that all the enzymes of the urea cycle are induced physiologically by an agent or agents as yet unidentified.

scholarly journals Regulation of tyrosine aminotransferase in foetal rat liver

1980 ◽  
Vol 186 (2) ◽  
pp. 609-612 ◽  
Author(s):  
S M Andersson ◽  
N C Räihä ◽  
J J Ohisalo
Keyword(s):  
Enzyme Activity ◽  
Methyl Ester ◽  
Cyclic Amp ◽  
Organ Culture ◽  
Rat Liver ◽  
Tyrosine Aminotransferase ◽  
Dibutyryl Cyclic Amp ◽  
Adult Rat ◽  
Foetal Rat

A specific tyrosine aminotransferase, separate from the aspartate aminotransferases, is present in low concentration in foetal rat liver at the 21st day of gestation. Intraperitoneal injections of tyrosine methyl ester into the foetuses in utero increase the activity 2-fold, whereas glucose injections decrease it. Tyrosine, dexamethasone and dibutyryl cyclic AMP induce the enzyme activity in organ culture to the same extent as in adult rat liver in vivo.

scholarly journals The hormonal regulation of enzymes in prenatal and postnatal rat liver. Effects of adenosine 3′,5′-(cyclic)-monophosphate

1969 ◽  
Vol 115 (1) ◽  
pp. 19-24 ◽  
Author(s):  
Olga Greengard
Keyword(s):  
Growth Hormone ◽  
Hormonal Regulation ◽  
Time Course ◽  
Tyrosine Aminotransferase ◽  
Cyclic Monophosphate ◽  
Sequential Development ◽  
Foetal Liver ◽  
Old Rats ◽  
Postnatal Rats ◽  
Do So

1. The administration of glucagon, cAMP [adenosine 3′,5′-(cyclic)-monophosphate], BcAMP [6-N-2′-O-dibutyryladenosine 3′,5′-(cyclic)-monophosphate] or adrenaline to foetal rats during the last 2 days of gestation evoked the appearance of tyrosine aminotransferase and enhanced the accumulation of glucose 6-phosphatase in the liver. In foetuses 1–2 days younger only BcAMP was effective. After birth liver glucose 6-phosphatase no longer responds to glucagon or BcAMP. Tyrosine aminotransferase is still inducible by these agents in 2-day-old rats, but not in 50-day-old rats. After adrenalectomy of adults glucagon or BcAMP can enhance the induction of the enzyme by hydrocortisone. The results indicate that the ability to synthesize tyrosine aminotransferase and glucose 6-phosphatase when exposed to cAMP develops sooner than the ability to respond to glucagon with an increase in the concentration of cAMP; the responsiveness of enzymes to different hormones changes with age. A scheme illustrating the sequential development of competence in regulating the level of an enzyme is presented. 2. Actinomycin inhibited the effects of glucagon and BcAMP on liver tyrosine aminotransferase and glucose 6-phosphatase in foetal rats. Growth hormone, insulin and hydrocortisone did not enhance the formation of these enzymes. 3. The time-course of accumulation of glucose 6-phosphatase in the kidney is different from that in the liver. Hormones that increase the accumulation in foetal liver do not do so in the kidney of the same foetus or in the livers of postnatal rats.

TESTOSTERONE SECRETION BY FOETAL RAT TESTES IN VITRO

1976 ◽  
Vol 71 (2) ◽  
pp. 231-238 ◽  
Author(s):  
RÉGINE PICON
Keyword(s):  
Cyclic Amp ◽  
Synthetic Medium ◽  
Functional Differentiation ◽  
Dibutyryl Cyclic Amp ◽  
Testosterone Secretion ◽  
Testosterone Production ◽  
Foetal Rat

SUMMARY Testosterone secretion by foetal rat testes (13½–21½ days of gestation) explanted for 3 days in a synthetic medium was measured every 24 h by radioimmunoassay. During the first day of explantation, the foetal testis produced, respectively, 1013 ± 132, 8734 ± 1118, 9179 ± 2185 and 3886 ± 309 (s.e.m.) pg/testis when explanted at 14½, 16½, 18½ and 21½ days respectively. Testosterone production by 13½-day-old testes was not detectable on the first day of culture, but appeared on subsequent days. Daily testosterone secretion increased on the 2nd and 3rd days of culture in 14½-day-old testes and decreased in older stages. These results suggest that the functional differentiation of the testis is independent of stimulatory factors like gonadotrophins. Dibutyryl cyclic AMP was found to stimulate testosterone production significantly from 14½ days of gestation onwards.

scholarly journals Factors that prevent the premature appearance of glucokinase in neonatal rat liver

1980 ◽  
Vol 186 (3) ◽  
pp. 817-826 ◽  
Author(s):  
M J O Wakelam ◽  
M B Allen ◽  
D G Walker
Keyword(s):  
Angiotensin Ii ◽  
Cyclic Amp ◽  
Insulin Release ◽  
Rat Liver ◽  
Neonatal Rat ◽  
Oral Glucose ◽  
Dibutyryl Cyclic Amp ◽  
Simultaneous Treatment ◽  
Physiological Factors ◽  
Glucose Administration

1. The physiological factors that prevent the precocious appearance of glucokinase activity in the 13-day-old rat that can be induced by oral glucose administration were explored. 2. Evidence is presented that the galactose component of milk sugar is inhibitory. In the absence of this inhibitory galactose, the amount of glucose necessary to effect appreciable induction is greater than that present in milk. 3. The induction is prevented both by administration of mannoheptulose, which inhibits insulin release, and by excess insulin; the amount of insulin available therefore seems to be critical. 4. The inhibition of induction by galactose does not appear to be via competition with glucose but by enhancing insulin release and thereby making this excessive. The relative amounts of glucose and insulin appear to be important in regulating glucokinase induction. 5. The precocious induction of glucokinase by glucose is inhibited by simultaneous treatment with approriate amounts of adrenaline, glucagon, dibutyryl cyclic AMP or isoprenaline but not by vasopressin or angiotensin II. 6. No single cause of glucokinase induction in neonatal rat liver can be recognized. The process is subject to regulation by many factors at a time subsequent to when competence to synthesize the enzyme has been established.

Effect of epinephrine and dibutyryl cyclic AMP on Δ5-desaturation activity of rat liver microsomes

Lipids ◽  
1980 ◽  
Vol 15 (12) ◽  
pp. 1064-1066 ◽  
Author(s):  
I. N. T. de Gomez Dumm ◽  
M. J. T. de Alaniz ◽  
R. R. Brenner
Keyword(s):  
Cyclic Amp ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Rat Liver Microsomes ◽  
Dibutyryl Cyclic Amp ◽  
Desaturation Activity
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