scholarly journals Glucose metabolism in the newborn rat. Hormonal effects in vivo

1973 ◽  
Vol 134 (4) ◽  
pp. 899-906 ◽  
Author(s):  
Keith Snell ◽  
Deryck G. Walker
Keyword(s):  
Cyclic Amp ◽  
Intraperitoneal Injection ◽  
Actinomycin D ◽  
Specific Radioactivity ◽  
Liver Glycogen ◽  
Newborn Rats ◽  
Dibutyryl Cyclic Amp ◽  
Lactate Formation ◽  
Glucose Formation

1. The concentrations of liver glycogen and plasma d-glucose were measured in caesarian-delivered newborn rats at time-intervals up to 3h after delivery after treatment of the neonatal rats with glucagon, dibutyryl cyclic AMP, cortisol or cortisol+dibutyryl cyclic AMP. Glycogenolysis was promoted by glucagon or dibutyryl cyclic AMP in the third hour after birth but not at earlier times. Cortisol and dibutyryl cyclic AMP together (but neither agent alone) promoted glycogenolysis in the second hour after birth, but no hormone combination was effective in the first postnatal hour. 2. The specific radioactivity of plasma d-glucose was measured as a function of time for up to 75 min after the intraperitoneal injection of d-[6-14C]glucose and d-[6-3H]glucose into newborn rats at delivery and after treatment with glucagon or actinomycin D. Glucagon-mediated hyperglycaemia at this time was due to an increased rate of glucose formation and a decreased rate of glucose utilization. Actinomycin D prevented glucose formation and accelerated the rate of postnatal hypoglycaemia. 3. The specific radioactivity of plasma l-lactate and the incorporation of 14C into plasma d-glucose was measured as a function of time after the intraperitoneal injection of l-[U-14C]lactate into glucagon- or actinomycin D-treated rats immediately after delivery. The calculated rates of lactate formation were unchanged by either treatment, but lactate utilization was stimulated by glucagon administration. Glucagon stimulated and actinomycin D diminished 14C incorporation into plasma d-glucose. 4. The factors involved in the initiation of glycogenolysis and gluconeogenesis in the rat immediately after birth are discussed.

scholarly journals Glucose metabolism in the newborn rat. Temporal studies in vivo

1973 ◽  
Vol 132 (4) ◽  
pp. 739-752 ◽  
Author(s):  
Keith Snell ◽  
Deryck G. Walker
Keyword(s):  
Intraperitoneal Injection ◽  
Glucose Utilization ◽  
Ketone Bodies ◽  
Post Partum ◽  
Specific Radioactivity ◽  
Liver Glycogen ◽  
Uterine Environment ◽  
Lactate Formation ◽  
Lactate Utilization

1. The concentrations of plasma d-glucose, l-lactate, free fatty acids and ketone bodies and of liver glycogen were measured in caesarian-delivered newborn rats at time-intervals up to 4h after delivery. Glucose and lactate concentrations decreased markedly during the first hours after delivery, but there was a delay of 60–90min before significant glycogen mobilization occurred. 2. The specific radioactivity of plasma d-glucose was measured as a function of time for up to 75min after the intraperitoneal injection of d-[6-14C]glucose and d-[6-3H]glucose into caesarian-delivered rats at 0, 1 and 2h after delivery. Calculations revealed that there was an appreciable rate of glucose formation at all ages studied, but immediately after delivery this was exceeded by the rate of glucose utilization. Around 2h post partum the rate of glucose utilization decreased dramatically and this coincided with a reversal of the immediately postnatal hypoglycaemia. 3. The specific radioactivity of plasma l-lactate and the incorporation of 14C into plasma d-glucose and liver glycogen was measured as a function of time after the intraperitoneal injection of l-[U-14C]lactate into rats immediately after delivery. The logarithm of the specific radioactivity of plasma l-[U-14C]lactate decreased linearly with time for at least 60min after injection and the calculated rate of lactate utilization exceeded the rate of lactate formation. 4. 14C incorporation into plasma d-glucose was maximal from 30–60min after injection of l-[U-14C]lactate and the amount incorporated at 60min was 23% of that present in plasma lactate. Although 14C was also incorporated into liver glycogen the amount was always less than 3% of that present in plasma glucose. 5. The results are discussed in relationship to the adaptation of the newly born rat to the extra-uterine environment and the possible involvement of gluconeogenesis at this time before feeding is established.

scholarly journals Regulation of the synthesis of lutropin-induced protein in rat testis Leydig cells

1978 ◽  
Vol 170 (1) ◽  
pp. 9-15 ◽  
Author(s):  
Felix H. A. Janszen ◽  
Brian A. Cooke ◽  
Maria J. A. Van Driel ◽  
Henk J. Van Der Molen
Keyword(s):  
Protein Synthesis ◽  
Cyclic Amp ◽  
Leydig Cells ◽  
Actinomycin D ◽  
Polyacrylamide Gel Electrophoresis ◽  
Phosphodiesterase Inhibitor ◽  
Dibutyryl Cyclic Amp ◽  
Rat Testis ◽  
Stimulation Of

The mechanism of action of lutropin on the stimulation of the synthesis of a specific lutropin-induced protein in rat testis Leydig cells was investigated. Lutropin-induced protein has a mol.wt. of approx. 21000 and is detected by labelling the Leydig-cell proteins with [35S]methionine, followed by separation by polyacrylamide-gel electrophoresis and radioautography of the dried gel. The incorporation of35S into lutropin-induced protein was used as an estimate for the synthesis of the protein. Incubation of Leydig cells with dibutyryl cyclic AMP or cholera toxin also resulted in the stimulation of synthesis of the protein. Synthesis of lutropin-induced protein, when maximally stimulated with 100ng of lutropin/ml, could not be stimulated further by addition of dibutyryl cyclic AMP. Addition of 3-isobutyl-1-methylxanthine, a phosphodiesterase inhibitor, further increased synthesis of the protein in the presence of a submaximal dose of lutropin (10ng/ml) but not in the absence of lutropin or with maximal amounts of lutropin (100 and 1000ng/ml). Actinomycin D prevented the effect of lutropin on the stimulation of lutropin-induced protein synthesis when added immediately or 1h after the start of the incubation, but not when added after 5–6h. This is interpreted as reflecting that, after induction of mRNA coding for lutropin-induced protein, lutropin had no influence on the synthesis of the protein in the presence of actinomycin D. Synthesis of the protein was also stimulated in vivo by injection of choriogonadotropin into rats 1 day after hypophysectomy, and the time course of this stimulation of lutropin-induced protein synthesis in vivo was similar to that obtained by incubating Leydig cells in vitro with lutropin. From these results it is concluded that stimulation of lutropin-induced protein synthesis by lutropin is most probably mediated by cyclic AMP and involves synthesis of mRNA.

scholarly journals The separate roles of glucose and insulin in the induction of glucokinase in hepatocytes isolated from neonatal rats

1981 ◽  
Vol 196 (2) ◽  
pp. 383-390 ◽  
Author(s):  
M J Wakelam ◽  
D G Walker
Keyword(s):  
Protein Synthesis ◽  
Cyclic Amp ◽  
Actinomycin D ◽  
Neonatal Rats ◽  
Dibutyryl Cyclic Amp ◽  
Subsequent Effect ◽  
Old Rats ◽  
Effect Of Glucose

1. The specificity of the effect of glucose on the induction of glucokinase activity that occurs when hepatocytes freshly isolated from 13-day-old rats are incubated in Medium 199 together with insulin [Wakelam & Walker (1980) FEBS Lett. 111, 115-119] was examined. A pattern that is different from other known effects of glucose is found, and metabolism of this compound is not necessarily to account for this particular effect. 2. The effects of a raised glucose concentration and of insulin on the induction can be separated. The hexose initiates the process in the absence of insulin in a manner that is sensitive to actinomycin D but not to cycloheximide. The subsequent effect of insulin is dependent on the prior effect of glucose or other positive analogue, does not require the presence of glucose and is inhibited by cycloheximide but not by actinomycin D. 3. Induction of glucokinase in vitro in hepatocytes from neonatal animals is inhibited by adrenaline, glucagon and dibutyryl cyclic AMP, but not by vasopressin or angiotensin II. The inhibition by cyclic AMP is on the stage requiring insulin and is comparatively specific, because total protein synthesis is not apparently diminished. 4. The implications of these results are discussed with reference to possible mechanisms of induction and to the situation in vivo.

scholarly journals Role of adrenaline and cyclic AMP in appearance of tyrosine aminotransferase in perinatal rat liver

1980 ◽  
Vol 190 (3) ◽  
pp. 685-690 ◽  
Author(s):  
A V Ghisalberti ◽  
J G Steele ◽  
M H Cake ◽  
M C McGrath ◽  
I T Oliver
Keyword(s):  
Cyclic Amp ◽  
Culture Medium ◽  
Actinomycin D ◽  
Cultured Cells ◽  
Tyrosine Aminotransferase ◽  
Newborn Rats ◽  
Aminotransferase Activity ◽  
Dibutyryl Cyclic Amp ◽  
Old Rats

1. Adrenaline increased hepatic tyrosine aminotransferase activity when injected into foetal rats or 2-day-old rats. 2. The inhibition of the postnatal increase in tyrosine aminotransferase activity which occurred in adrenalectomized newborn rats rapidly overcome by injection of adrenaline or dibutyryl cyclic AMP. 3. The effects of adrenaline or dibutyryl cyclic AMP on the tyrosine aminotransferase activity in foetal, adrenalectomized newborn and 2-day-old rats could be partially or completely blocked by prior treatment with actinomycin D. 4. Dibutyryl cyclic AMP induced tyrosine aminotransferase activity in hepatocytes cultured from 15-day foetal rats in glucocorticoid-free medium. 5. Actinomycin D at 0.2 microgram/ml in the culture medium completely prevented the induction of tyrosine aminotransferase activity by dibutyryl cyclic AMP in cultured cells. 6. The results suggest that adrenaline and cyclic AMP stimulate a transcriptional event during induction of tyrosine aminotransferase in perinatal 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.

ACTION OF KI, THYROXINE AND CYCLIC AMP ON [3H]URIDINE INCORPORATION INTO THE RNA OF THYROID SLICES

1976 ◽  
Vol 83 (2) ◽  
pp. 313-320 ◽  
Author(s):  
Mario A. Pisarev ◽  
Leonardo O. Aiello ◽  
Diana L. Kleiman de Pisarev
Keyword(s):  
Cyclic Amp ◽  
Inhibitory Action ◽  
Rna Synthesis ◽  
Actinomycin D ◽  
Protein Biosynthesis ◽  
Rna Degradation ◽  
Precursor Pool ◽  
Rna Precursor

ABSTRACT Potassium iodide (KI) has been shown to impair thyroid protein biosynthesis both in vivo and in vitro. The present study was performed in order to clarify its mechanism of action. Ribonucleic acid (RNA) synthesis was studied in beef thyroid slices with either [32P] or [3H]-uridine as labelled precursors. Both KI and thyroxine (T4) at 10−5 m significantly decreased RNA labelling under our conditions. In other experiments RNA degradation was examined in pulse-labelled and actinomycin D-treated slices. KI did not modify the degradation of the [3H]-RNA thus indicating that it interferes with the biosynthesis rather than with the degradation of RNA. Taking the perchloric acid soluble radioactivity as a rough index of the precursor pool the present results would indicate an action at this level. Both KClO4 and methylmercapto-imidazole relieved the gland from the inhibitory action of KI, supporting the view that an intracellular and organified form of iodine is responsible for this action. Since T4 also reproduced the effects of KI on RNA synthesis we would like to propose iodothyronines as the intermediates of this action. Cyclic AMP has been shown to stimulate thyroid protein biosynthesis. The present results demonstrate an action at the RNA level. Cyclic AMP increased both the PCA-soluble and RNA-linked radioactivity, thus suggesting an effect at the RNA precursor pool. KI at 10−5 m blocked the action of 2 mm cyclic AMP.

scholarly journals Studies in lipogenesis in vivo. Fatty acid and cholesterol synthesis during starvation and re-feeding

1966 ◽  
Vol 101 (3) ◽  
pp. 811-818 ◽  
Author(s):  
GR Jansen ◽  
ME Zanetti ◽  
CF Hutchison
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Intraperitoneal Injection ◽  
Cholesterol Synthesis ◽  
Liver Glycogen ◽  
Acid Synthesis ◽  
Tracer Dose ◽  
Intraperitoneal Dose

1. Lipogenesis in vivo has been studied in mice given a 250mg. meal of [U-(14)C]glucose (2.5muc) or given an intraperitoneal injection of 25mug. of [U-(14)C]glucose (2.0muc). 2. The ability to convert a [U-(14)C]glucose meal into fatty acid was not significantly depressed by 6-7hr. of starvation. In contrast, incorporation of (14)C into fatty acid in the liver after the intraperitoneal dose of [(14)C]glucose was depressed by 80% and by more than 90% by 1 and 2hr. of starvation respectively. Carcass fatty acid synthesis from the [U-(14)C]glucose meal was not depressed by 12hr. of starvation, whereas from the tracer dose of [U-(14)C]glucose the depression in incorporation was 80% after 6hr. of starvation. 3. Re-feeding for 3 days, after 3 days' starvation, raised fatty acid synthesis and cholesterol synthesis in the liver fivefold and tenfold respectively above the levels in non-starved control mice. These increases were associated with an increased amount of both fatty acid and cholesterol in the liver. 4. After 18hr. of starvation incorporation of a [U-(14)C]glucose meal into carcass and liver glycogen were both increased threefold.

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