Investigation of thyroxine monodeiodinase activity in the liver, kidney and brown adipose tissue of foetal and neonatal rabbit

The maturation of the 5'- and 5-monodeiodinase system in liver, kidney and brown adipose tissue of rabbits, during the foetal period (from 21 days of gestation to birth) and the neonatal period (from birth to 3 weeks of life) was studied. A sudden increase of 5'- and 5-monodeiodinase activity in liver and kidney 3 days before birth was observed, falling to a nadir at day 3 after birth. Foetal and neonatal serum T4, T3 and rT3 concentration were very low and rose progressively with age, reaching adult values at about day 21. In the foetal brown adipose tissue high 5'-monodeiodinase and low 5-monodeiodinase activity was found. The 5'-monodeiodinase decreased during the first days of life whereas the 5-monodeiodinase activity remained at a low stable level until day 3 when the activities of both enzymes increased. The increase of conversion rate of T4 to T3 and rT3 in liver and kidney well correlate with the triiodothyronines concentration in serum from day 3 after birth.     

The appearance, properties, and functions of gluconeogenic enzymes in the liver and kidney of the guinea pig during fetal and early neonatal development.

The changes in the activity and properties of the four gluconeogenic enzymes have been followed during development of the guinea pig. Pyruvate carboxylase was almost exclusively mitochondrial and kinetically identical to the adult liver enzyme and did not appear in significant activity until after day 50 when it rose to values several times higher than those in the adult liver, then fell after birth. Little activity was detected in the fetal kidney. Phosphoenolpyruvate carboxylase appeared in the fetal liver from day 30 on, both in the mitochondrial and cytoplasmic fractions. The cytoplasmic enzyme was kinetically and chromatographically identical to the mitochondrial enzyme of the fetal and maternal liver. After birth the activity of the cytoplasmic enzyme increased and that of the particulate enzyme fell. Fetal kidney activity appeared several days before birth. Fructose 1,6-diphosphatase and glucose 6-phosphatase appeared in the fetal liver and kidney after day 40; the former showed no postnatal change while the latter rose 10-fold after birth. Fetal liver fructose 1,6-diphosphatase was more sensitive to AMP and fructose 1,6-diphosphate inhibition but was chromatographically indistinguishable from the maternal liver enzyme. Despite the presence of the gluconeogenic enzymes, gluconeogenesis and glyconeogenesis were not detected in the fetal liver until 7–9 days before birth. While the synthesis of glyceride-glycerol from 3-carbon compounds was detected from 35–40 days onwards and some of the gluconeogenic enzymes participate in that pathway, gluconeogenesis was not detected in the fetal kidney.     

Development of the metanephric kidney. Protein and nucleic acid synthesis

The metanephric kidney was studied in fetal and older mice beginning at 16 days after mating of the parents. Polyribosomes from fetal kidneys labeled in vitro with 14C-labeled amino acids had 10-20 times more acid-precipitable radioactivity associated with them than polysomes from adult kidneys similarly labeled. Between 3 and 6 days after birth the rate incorporation of labeled amino acids by polyribosomes from neonatal kidneys declined sharply to only twice the value found for adult kidneys. There was no change in the shape of the polyribosome profile with increasing age, but before birth few, if any, ribosomes were bound to membranes compared with 20% 2 days after birth and between 20 and 30% in the adult. Total protein represented less than 10% of the wet weight in the fetal kidney but increased to 17% of the wet weight in the adult kidney. There was a steady decline in the concentration of RNA and DNA with respect to dry weight throughout kidney development. DNA concentration declined more rapidly than RNA concentration, so that the milligram to milligram ratio of RNA to DNA increased. In males the RNA/DNA ratio was stable at 1.3 at 40 days after birth; but in females the decline in DNA concentration was more protracted, and at 200 days after birth the RNA/DNA ratio was only 0.99. Thus, total nucleic acids show only gradual changes in concentration throughout development of the kidney, but a sharp change in the synthetic activity of the ribosomes and in their binding to membranes occurs in kidneys soon after birth.     

Hexokinase isoenzymes in tissues of the adult and developing guinea pig

Changes in the activities and isoenzyme distribution of hexokinase were determined in a number of tissues during the development of the guinea pig. The total activity in the fetal liver showed a large fall during the second half of gestation to reach adult values by term. With normal diet the fetal, neonatal, and adult livers had isoenzymes I and III but little or no detectable IV (glucokinase). The fetal liver had predominantly type I, but the proportion of type III increased during development. The kinetics of the guinea pig isoenzymes were similar to those reported for the rat. Two additional isoenzymes with mobility between I and II were detected in the fetal liver and blood. They appear to have kinetic properties similar to type I. Detectable liver glucokinase activity was induced by glucose administration to adult guinea pigs. The total activity in kidney, brain and skeletal muscle showed a postnatal rise while in the fetal heart it was high and declined after birth. These tissues contained predominantly type I with varying proportions of type III hexokinase. The ratio of particulate-bound to soluble hexokinase varied from tissue to tissue. All except the liver showed a significant increase in binding after birth. The changes are discussed in relation to the control of glucose utilization in the fetal and neonatal periods.     

Biochemical and Molecular Responses to Loss of Renal Mass: Atpase and Cyclic Nucleotides: Evidence for Altered Cyclic Nucleotide Metabolism During Compensatory Renal Hypertrophy and Neonatal Kidney Growth

In adult male Sprague-Dawley rats contralateral nephrectomy was followed by an initial fall of the concentration of cGMP in renal cortical tissue followed by a rise to a peak level of 300 percent of the initial concentration within two hours. cGMP concentration in the remaining renal cortex remained at about 300 percent of the initial value during the subsequent 72 hours and slowly declined to 150-200 percent in the following two weeks. The changes in cGMP concentration were due to exactly parallel changes in the soluble fraction of renal cortical guanylate cyclase activity, while cGMP-phosphodiesterase activity remained unchanged. cAMP concentration after contralateral nephrectomy fell significantly by about 25 percent within two hours and remained below baseline level for up to eight hours. In the kidneys of newborn rats the concentration of cAMP was approximately one-half that found in adult kidneys: it slightly fell between the fourth and the seventh day after birth and subsequently continuously rose to reach adult values approximately two weeks after birth. The concentration of cGMP was significantly greater four days after birth than in adult rats, further rose between the fourth and the seventh day after birth and subsequently gradually declined to adult levels. The increased cGMP concentration appears to be due to an increase of guanylate cyclase activity in total kidney homogenates which, in turn, was mainly due to an increase of the particulate (membrane-bound) fraction of the enzyme. cGMP-phosphodiesterase activity, however, was also increased in respect to adult levels, one or three weeks after birth. Renal growth from the seventh day after birth to adulthood is accompanied by a continuous increase of the ratio cAMP/cGMP. Removal of one kidney four to seven days after birth resulted in a slower increase of this ratio. The data suggest that cGMP may trigger renal growth and that increases of cGMP concentration in the kidneys are the result of a primary increase in the activity of guanylate cyclase.     

Glycerolkinase--a regulatory enzyme of gluconeogenesis?

1. The development of glycerolkinase before and after birth was investigated in liver and kidney of rat and hamster. In rat liver, enzyme activity increased very slowly before birth and rapidly thereafter, reaching adult values at the 6th day of postnatal life. In hamster liver, glycerolkinase was considerably elevated already in utero, increased dramatically within the 1st day of postnatal life and reached adult values at the end of the 1st week. The development of hepatic glycerolkinase was compared with that of hepatic phosphoenolpyruvate carboxykinase of rat and hamster up to the 20th day of postnatal life. The different time-courses of the levels of these two enzymes before and after birth as well as the known kinetics of serum insulin, glucagon and corticosterone during that time suggested that none of these hormones is involved in the perinatal development of hepatic glycerolkinase activity. In contrast to liver, kidney glycerolkinase activity in both, rat and hamster, showed a delayed increase during the first week of postnatal life followed by a more pronounced elevation to adult values within the following 2 weeks. 2. When liver and kidney glycerolkinase activity was investigated during starvation (+/- refeeding), in alloxan diabetes(+/- insulin) and after adrenalectomy (+/- cortisol) no significant change in enzyme activity per g tissue could be detected either in liver or in kidney. However, total hepatic glycerolkinase activity was diminished during starvation as a consequence of decreasing liver weight. 3. Incorporation of U-[14C]-glycerol into CO2, lipids and glucose + glycogen by rat liver and kidney cortex slices was studied under the above gluconeogenetic conditions. Despite unchanged glycerolkinase activity in both organs, gluconeogenesis from glycerol was enhanced during starvation and in chronic alloxan diabetes, and could be reversed by refeeding and insulin replacement, respectively. 4. Feeding 20% of linolic acid to normal, alloxan-diabetic or adrenalectomized rats resulted in a significant increase in glycerolkinase activity in liver but not in kidney. 5. From the present findings it is suggested that the first step of gluconeogenesis from glycerol in liver and kidney is not influenced by glucagon, insulin and glucocorticoids, which are generally believed to regulate the rate of gluconeogenesis from non-glycerol precursors, but probably by the change in blood glycerol concentration.     

D-aspartate oxidase, a peroxisomal enzyme in liver of rat and man

By means of subcellular fractionation D-aspartate oxidase was shown to be localized in peroxisomes in rat and human liver. The oxidase from both sources was most active on D-aspartate and N-methyl-D-aspartate. In different rat tissues, the highest enzyme activity was found in kidney, followed by liver and brain. In these tissues, oxidase activities became detectable 1-4 days after birth, reaching adult values after 4 weeks. Analysis of liver samples from patients with Zellweger syndrome, a generalized peroxisomal dysfunction, demonstrated no significant deficiency of this particular oxidase.     

CYSTATHIONINE SYNTHESIS AND DEGRADATION IN BRAIN, LIVER AND KIDNEY OF THE DEVELOPING MONKEY

Abstract— The concentration of cystathionine, along with the specific activities of the enzymes involved in its synthesis and degradation, cystathionine synthasc and cystathionase, respectively, have been measured in brain, liver and kidney of the developing Rhesus monkey from mid-gestation, through birth and neonatal life, to maturity. The concentration of cystathionine and the specific activity of cystathionine synthase are low in fetal brain. Both parameters increase slowly after birth and reach values found in adult brain at approx 3 months of postnatal age. The activity of cystathionase in brain is low throughout development.
Liver provides a direct contrast in that the concentration of cystathionine and the specific activity of cystathionine synthase are high in the fetus, decreasing rapidly after birth to values found in the adult by 2 weeks of postnatal age. Cystathionase activity is low in fetal liver and increases slowly after birth reaching values found in adult liver after 2–3 months. Kidney has no more than trace amounts of cystathionine throughout development, higher activity of cystathionine synthase in the fetus than in the adult and high, unchanged activity of cystathionase throughout the period of development studied.
These results indicate that the high concentrations of cystathionine found in primate brain are reached postnatally and suggest that this high concentration of cystathionine may be associated with the functioning of mature brain.     

Nicotinamide methylation tissue distribution,developmental and neoplastic changes

The distribution of cytosolic activity of nicotinamide:S-adenosylmethionine methyltransferase (nicotinamide methylase, EC 2.1.1.1) in normal tissues from adult rat and mouse and in tumors and the change in the enzyme activity during the the development of rat tissues were studied. (1) Rat liver exhibited the highest nicotinamide methylase activity among all adult tissues tested; other rat tissues, like adrenal, pancreas, kidney, brain and mouse tissues, had only less than 15% of the adult rat liver activity. (2) 3 days before birth, fetal liver showed a very low nicotinamide methylase activity (2% of adult rat liver), which, however, increased already 1 day before birth and reached the adult level on the day 28 after birth. (3) In a variety of hepatomas and ascites tumors, an inverse correlation, with some exceptions, between tumor growth rate and nicotinamide methylase activity could be seen. In all hepatomas, with the exception of Morris hepatoma 5123tc, nicotinamide methylase activity was significantly decreased in comparison to normal adult rat liver. The highly malignant Zajdela hepatoma, Yoshida sarcoma, sarcoma 180 and Ehrlich ascites tumor methylated nicotinamide only at a negligibly low rate. (4) Cultured RLC cells (an established rat liver cell line) from the stationary growth phase or G₁-arrested RLC cells had about half of the adult rat liver activity, yet the activity was 70% higher than that of the logarithmically growing RLC cells.     

Perinatal changes in amylase and serum corticosterone levels in rats

In rats amylase activity in the pancreas increased greatly from day 15 of gestation to a maximum on day 21. Then it decreased to less than one-tenth of this maximum value on about day 5 after birth. It increased again about 15 days after birth and reached the adult level about 30 days after birth.No amylase activity was in the parotid gland before birth: it appeared about 12 days after birth and reached the adult level, which was higher than that in the pancreas, about 30 days after birth.The serum corticosterone level was as high as the adult level before birth. Then it decreased to less than one-tenth of the adult level 5 days after birth and increased again from 15 to 25 days after birth to the adult level. The developmental change in the serum corticosterone level seemed to influence amylase activity in the pancreas both before and after birth, and that in the parotid gland only after birth.The serum contained both pancreatic and paratoid type isozymes of amylase until 1 day after birth but only the parotid type from 3 days after birth.     

Activity and isoenzyme patterns of glycolytic enzymes during perinatal development of rat lung

The enzymes hexokinase (EC 2.7.1.1), phosphofructokinase (EC 2.7.1.11), enolase (EC 4.2.1.11) and pyruvate kinase (EC 2.7.1.40) were studied in rat lung during development starting at day 16 of gestation (day-6) until 5 days after birth. During gestation, the activities of hexokinase type II, enolase and pyruvate kinase decreased and reached adult values at birth or shortly thereafter. Hexokinase type I remained relatively constant and the decrease of soluble type II hexokinase was compensated for by an increment of particle-bound hexokinase starting at day 20 of gestation until birth. In contrast, phosphofructokinase activity increased until day 20 of gestation followed by a rapid fall in activity until 2 days after birth. Except for hexokinase no isoenzyme shifts were observed in the period of observation. The results are discussed with respect to the proposed relationship between glycogen breakdown and surfactant synthesis during the perinatal period and suggest a regulatory role for phosphofructokinase in this process.     

Prenatal and postnatal changes in the content and species of ferritin in rat liver

The iron and ferritin content of rat liver and the species of ferritin present were examined from 4 days before to 3 weeks after birth. 1. Total iron and ferritin iron accumulated rapidly during the last days of gestation and from the second postnatal day underwent a steady depletion. 2. The amount of iron deposited before birth in the liver of each pup varied inversely with litter size and could be increased moderately by injection of iron into the mother before mating. 3. Intraperitoneal injection of iron 1 day after birth doubled the concentration of total iron, ferritin iron and ferritin protein in the liver over the next 24h, but at 3 weeks after birth it raised the very low concentrations of iron and ferritin severalfold. 4. As shown by electrophoretic migration, ferritin and dissociated ferritin subunits prepared from the livers of rats from 4 days before to 3 weeks after birth differed from those of adult liver ferritin and were indistinguishable from those of adult kidney and spleen ferritin. Treatment with iron at 3 weeks of age induced formation of a ferritin with electrophoretic properties resembling those of adult liver. It is concluded that iron given at this stage of development may activate the genetic cistron for adult liver ferritin.     

Changes in the activities of the enzymes of hepatic ketogenesis in the rat between late fetal life and weaning.

The activities of hydroxymethylglutaryl-CoA synthase and hydroxymethylglutaryl-CoA lyase have been determined in the mitochondria and cytosol of the liver during development of the rat. Both mitochondrial enzymes exhibit similar developmental patterns with rapid rises in activity after birth, peaks of activity during early and late suckling and a trough during the mid-suckling period and a slight fall in activity (to the adult values) after weaning. Both cytosolic enzymes have low activities at all ages studied and exhibit no major developmental changes.     

Biochemical and Molecular Responses to Loss of Renal Mass: Atpase and Cyclic Nucleotides: Cyclic Nucleotide Concentrations in Relation to Renal Growth and Hypertrophy

In rats no consistent change in the concentration of cyclic GMP or cyclic AMP concentration was found in the renal cortex between 2 hours and seven days after unilateral nephrectomy. In regenerating liver tissue, between 2 hours and seven days after removal of one-third of the liver, there were no consistent changes in cyclic GMP concentrations, but cyclic AMP concentrations were higher than in controls. During postnatal growth, no consistent changes occurred in the cyclic GMP concentration of the spleen, the testes, the kidney cortex, the renal papilla, the liver or the ventricle between two and sixty days after birth. Cyclic AMP concentration on the other hand, in all these tissues with the exception of the spleen, was depressed between the twenty-first and fortieth day after birth, i.e., at a period of rapid growth. In the spleen, the concentration of cyclic AMP increased continuously from the second to the fifth day after birth. During renal parenchymal hyperplasia induced by a large intravenous dose of folic acid two days before sacrifice, the concentration of cyclic GMP in renal cortical tissue increased consistently. A model is proposed to explain the different patterns of changes in the cyclic nucleotide concentrations found.     

Changes in hepatic lipogenesis during development of the rat

1. Changes in the activities of ATP citrate lyase, ;malic' enzyme, glucose 6-phosphate dehydrogenase, pyruvate kinase and fructose 1,6-diphosphatase, and in the ability to incorporate [1-(14)C]acetate into lipid have been measured in the livers of developing rats between late foetal life and maturity. 2. In male rats the activities of those systems directly or indirectly concerned in lipogenesis (acetate incorporation into lipid, ATP citrate lyase and glucose 6-phosphate dehydrogenase) fall after birth and are maintained at a low value until weaning. After weaning these activities rise to a maximum between 30 and 40 days and then decline, reaching adult values at about 60 days. ;Malic' enzyme activity follows a similar course, except that none could be detected in the foetal liver. Pyruvate kinase activity is lower in foetal than in adult livers and rises to slightly higher than the adult value in the post-weaning period. Fructose 1,6-diphosphatase activity rises from a very low foetal value to reach a maximum at about 10 days but falls rapidly after weaning to reach adult values at about 30 days. 3. Weaning rats on to a high-fat diet caused the low activities of acetate incorporation, ATP citrate lyase, glucose 6-phosphate dehydrogenase and pyruvate kinase, characteristic of the suckling period, to persist. ;Malic' enzyme and fructose 1,6-diphosphatase activities were not altered appreciably. 4. No differences could be detected in hepatic enzyme activities between males and females up to 35 days, but after this time female rats gave higher values for acetate incorporation, glucose 6-phosphate dehydrogenase activity and ;malic' enzyme activity. 5. The results are discussed in relation to changes in alimentation and hormonal influences.     

Uridine kinase activities in developing, adult and neoplastic rat tissues.

Uridine kinase activities were found chiefly in the soluble fractions of rat tissues. In normal adults the activities ranged from 13 munits/g in skeletal muscle to 178 munits/g in colon. Enzyme activities in several rat neoplasms were significantly higher (e.g. in a fibrosarcoma, mammary carcinoma, renal carcinoma, pancreatic carcinoma and lymphocytic lymphoma, but not in a fast-growing Morris hepatoma). The activities were not related to tumour growth rates or sizes. In normal foetal liver, lung, brain, heart and kidney, uridine kinase concentrations equalled or exceeded those in the adult homologous tissue, but maximal activities in liver were reached 3--5 days post partum. In suckling rats the intestinal activity decreased substantially immediately after birth and normally did not rise again until late in the third postnatal week. Premature upsurges could be evoked by an injection of cortisol or by starvation of the pups overnight. Pancreatic activity was absent from 1-day-old rats, and only about 5% of the adult activity was reached by day 20; adult activities were attained rapidly after weaning. In pancreas, precocious formation or uridine kinase was elicited by overnight starvation of 2-week-old rats.     

ACTIVITIES OF SOME ENZYMES INVOLVED IN HOMOCYSTEINE METHYLATION IN BRAIN, LIVER AND KIDNEY OF THE DEVELOPING RHESUS MONKEY

Abstract— The specific activities of the enzymes responsible for remethylation of homocysteine to methionine. N⁵-methyltetrahydrofolate-homocysteine methyltransferase and betaine-homocysteine methyl-transferase, and of the enzyme responsible for transferring the β-carbon atom of serine to tetrahydrofolate. serine tetrahydrofolate 5,10-hydroxymethyltransferase, have been measured in brain, liver and kidney of the developing Rhesus monkey from mid-gestation, from birth and neonatal life to maturity. The specific activity of N⁵-methyltetrahydrofolate-homocysteine methyltransferase in all tissues is higher during late gestation and shortly after birth than it is in the adult, and in brain and liver it shows a positive correlation with increasing gestational age. Betaine-homocysteine methyltransferase activity is not measurable in brain. In liver it increases linearly during fetal and neonatal development until values found in the adult are reached. In kidney there is a sharp linear increase during the period of gestation studied. The drop at birth is followed by a sharp increase back to values noted at the end of gestation and thereafter a slow increase to values found in the adult. The specific activity of serine-tetrahydrofolate 5,10-hydroxymethyltransferase tends to be higher in fetal and early neonatal brain than it is in adult brain, whereas in liver and kidney it is low in the fetus and rises during development to reach values found in the adult some months after birth.     

Effect of Cortico-Striate Pathway Lesion on the Activities of Enzymes Involved in Synthesis and Metabolism of Amino Acid Neurotransmitters in the Striatum

The activities of several enzymes involved in the metabolism of aspartate and glutamate were measured in striatal (nucleus caudatus and putamen) homogenates 2-3, 6-7, and 35-40 days following frontoparietal and frontal cortical ablation. The activity of glutamine synthetase (GS) was substantially increased (46-48%) on the operated side 6-7 days following the lesion whereas smaller changes were observed at 2-3 and 35-40 days after lesion. In contrast, decreased levels of glutaminase and malate dehydrogenase (MDH) were observed by 6-7 days while no significant change was found at either 2-3 or 35-40 after the lesion. The activities of glutamate dehydrogenase (GDH) and glutamate decarboxylase (GAD) were elevated after 35-40 days whereas no changes in the levels of either GDH or aspartate aminotransferase (ASAT) were found at 2-3 or 6-7 days after the fronto-parietal decortication. When only the frontal cortex was removed quantitatively similar changes were observed in striatal GS and glutaminase activity. The content of glutamate and glutamine in the denervated striatum followed qualitatively the changes in glutaminase and GS. The results indicate that the degeneration of cortico-striatal terminals causes a profound glial reaction in the striatum, and both glutaminase and MDH are present in relatively high concentrations in the corticostriatal terminals.     

Changes in activities of some ammonia-metabolizing enzymes in the rat liver and the brain after chronic ethanol administration

The changes in the activities of ammonia-metabolizing enzymes in liver and brain after ethanol intoxication has been investigated in rats. After administration of ethanol 30% (w/v) 6g kg-1 for 4 weeks we found an increase in liver glutamate dehydrogenase and glutaminase activity. In brain tissue the glutaminase activity was significantly higher and glutamate dehydrogenase was significantly lower. Glutamine synthetase activity in liver and brain was practically unchanged. The reasons for these changes in the activities of some ammonia-metabolizing enzymes in liver and brain after ethanol ingestion have been discussed.     

Urea synthesis in the liver and kidney of developing sheep

In order to establish if the urea found in foetal fluids in sheep could be of foetal origin and whether there are changes in the ability of ovine liver to synthesise urea during foetal and postnatal development, the rates of urea production from ammonium and bicarbonate ions have been measured in liver and kidney slices from animals aged from 50 days conceptual age to 16 weeks after birth, and in pregnant and non-pregnant ewes. The activities of five enzymes directly involved in the biosynthesis of urea have also been determined.Urea was found to be synthesised by foetal liver from at least 50 days conceptual age at rates similar to those observed in adult ewes. Highest rates of urea synthesis per unit weight of liver were found immediately after birth. In the liver there were significant positive correlations between the rates of urea synthesis by slices and the activities of carbomoyl phosphate synthase (ammonia) (EC 2.7.2.5), argininosuccinate synthetase (EC 6.3.4.5) and argininosuccinate lyase EC 4.3.2.1). Ornithine carbomoyl transferase (EC 2.1.3.3) activity was highest in the livers of ruminating animals. Hepatic arginase activity (EC 3.5.3.1) was highest during the late foetal life and in the mature foetuses the activity was ten-fold greated than that in maternal liver.Urea was not synthesised from ammonia and bicarbonate in kidney slices and neither ornithine carbomoyl transferase activity nor argininosuccinate synthetase activity could be detected. The activity of renal arginase was at least 70 times less than that found in the liver and the highest activity was found in ruminating lambs.The changes observed in the activities of the urea cycle enzymes during development have been contrasted with those reported to occur in other species. It is concluded that there is no single factor regulating the activities of the five enzymes directly concerned with urea synthesis during development. The results support the hypothesis that in mammals the ability of the liver to synthesise urea in foetal life is related to renal development.