Developmental changes of glutamate dehydrogenase activity in rat liver mitochondria and its enhancement by branched-chain amino acids.

The developmental changes of glutamate dehydrogenase activity in the fetal and neonatal rat liver were investigated, as well as the effects of branched-chain amino acids on this enzyme. Hepatic glutamate dehydrogenase activity showed a marked increase at the end of the fetal period and peaked on the 5th day of neonate at approximately 3 times higher than the adult level. Glutamate dehydrogenase was activated by leucine, isoleucine, and valine in this order when they were added to isolated intact liver mitochondria in vitro. The enhancement of enzyme activity was more marked in fetal rats than in adults. In contrast, when branched-chain amino acids were added after disrupting the mitochondrial membrane by sonication, only leucine slightly activated glutamate dehydrogenase, while isoleucine and valine slightly inhibited its activity. Our findings suggest that glutamate may be actively synthesized in the developing rat liver mitochondria and then transaminated to other nonessential amino acids for protein synthesis, and that increased intramitochondrial branched-chain amino acid concentrations may enhance glutamate dehydrogenase activity. This anabolic metabolism will contribute to the fetal growth and development.     

Gamma-glutamyltranspeptidase in the rat liver after portacaval shunt.

Gamma-Glutamyltranspeptidase (GGTP) activity was studied in livers of rats submitted to an end-to-side portacaval shunt (PCS) and in developing animals. To correlate the evolution of the enzymatic activity measured in vitro, histochemical techniques were used to localize enzyme activity in liver tissue. The GGTP activity in the adult rats was low and amounted to 2.0 +/- 0.1 mumol/min/g. During fetal development the enzyme activity rose beginning on the 15th gestational day from 630 +/- 97 to 1,058 +/- 20 on the first postnatal day. Then the values declined and reached nearly adult values from the 10th postnatal day. After PCS the GGTP activity exhibited a three- to sixfold increase (130 +/- 69 to 371 +/- 131) as compared with unoperated adult controls (53 +/- 13). the highest levels corresponded to those observed between the 3rd and 5th postnatal day in the developing rats. The histochemistry of GTTP in the fetal and newborn liver showed a regular distribution of the enzyme as a fine deposit in the hepatocytes throughout the whole tissue. Ten days after birth the activity was low, at the same level as in the adult rat. In the period after PCS hepatocytes began to show signs of enzymatic activity at the periphery of the hepatic lobules, which subsequently spread through the whole lobules. The increase of GGTP activity after PCS equaled the activity found in fetal animals. That correlated well in both groups with the reappearance of histologically demonstrable enzyme activity in hepatocytes.     

Changes in Taurine and Other Free Amino Acid Levels in the Blood of Developing Fetuses

In human pregnancy, maternal and umbilical blood of the 22nd and 40th weeks of pregnancy and at parturition were submitted to the analysis of total free amino acids (FAA) by the amino acids analyzer. The neonatal blood was also submitted until the 9th day after birth. The content of FAA in the serum from the umbilical vein was higher than that from the maternal blood, and it decreased at the parturition term. However, the content of taurine kept a much higher level than the other amino acids until term, and then it decreased to the normal level on the 9th day after birth. In pregnant rats on the 17th, 18th and 19th days of gestation, the content of FAA in the serum from the umbilical vein and fetal artery was twice as high as that of the maternal serum. In amniotic fluid, FAA content was increased on the 20th day. On the contrary, the content of taurine in fetal blood was at the highest level on the 18th day, after which it decreased until the 20th day. The level of taurine in the carotid artery decreased on the 20th day. In the amniotic fluid, it was almost constant. When the pregnant rat was starved, the level of FAA was increased in both umbilical and fetal blood, but it was almost constant in the amniotic fluid. Taurine content was increased in maternal and fetal blood by starvation, and increased also by irradiation. When the degree of starvation proceeded, taurine content increased correspondingly in the fetal blood.     

Pancreatic insulikn-, glucagon-, and somatostatin-positive islet cell populatins during the perinatal development of the rat. I. Morphometric quantitation

Pancreatic insulin-, glucagon- and somatostatin-positive islet cell volumes were quantitated morphometrically during the developmental interval from 16 days post coitum to 10 days postnatal. There was a rapid increase in the alpha- and beta-cell populations during late fetal life. The beta-cells increased more rapidly and comprised the major portion of the islets after the 20th fetal day. After birth the rate of increase of both beta- and alpha-cells decreased but was greater than that of the surrounding exocrine pancreas during the early period of postnatal life. This resulted in an islet cell percentage of 5-6% of the total pancrease on day 6 postnatal. delta-Cells were present before birth but increased in volume density within the islet cell after birth. The implications of these morphological data to the interpretation of physiological studies are discussed.     

Fetal and neonatal mortality of small-for-gestational age infants

Fetal and neonatal mortality of small-for-gestational age (SGA) infants in 1968–1982 were studied in the region of the University Central Hospital of Turku, Finland. During the study period, there were 254 fetal and 127 neonatal deaths in SGA infants. The fetal mortality rate of SGA infants declined from 49.9/1000 to 14.0/1000. The neonatal mortality rate of SGA infants declined from 23.8/1000 to 8.3/1000. The severely SGA infants with a birth weight below the 2.5th percentile had three times higher neonatal mortality rates than SGA infants with a birth weight between the 2.5th and the 10th percentiles. The main causes of fetal deaths were maternal diseases, placental and cord complications and fetal malnutrition, even though there was a decline in all these groups. Malformations remained the main cause of neonatal death during the study period, while there was a decline in deaths due to asphyxia and respiratory distress syndrome (RDS). The high mortality rates of SGA infants emphasize the need for early diagnosis and special attention during pregnancy, delivery and the neonatal period.Abbreviations SGA small-for-gestational age - AGA appropriate-for-gestational age - UCHT University Central Hospital of Turku - RDS respiratory distress syndrome     

Morphometrical studies on perinatal development of glomerular components in rat

Perinatal development of rat glomerulus was studied morphometrically. The percentage volumes of the five glomerular components (epithelial cells, capillary, mesangium, glomerular basement membrane, and Bowman's space) were determined by point counting and the surface area of glomerular basement membrane per unit volume of glomerulus was done by intercept counting. Percentage volume of Bowman's space was significantly decreased between days 20 and 21 of gestation, indicating the rapid growth of glomerular tuft during the prenatal period. Though both the length of glomerular capillary per unit volume of glomerulus (Lv) and surface area of glomerular basement membrane per unit volume of glomerulus were gradually increased from fetal day 20 to neonatal day 3, remarkable increase in Lv was observed between fetal day 22 and neonatal day 1. This indicates that the rat glomerulus develops rapidly during this period to adapt to extrauterine environment after birth.     

Perinatal development of bilirubin UDP-glycosyltransferase activities in rat liver.

Bilirubin UDP-glucuronyltransferase and UDP-xylosyltransferase activity could already be demonstrated in rat liver from day 19 of fetal life onwards (4 days before birth). Bilirubin-glucuronide was present in hepatocytes of 21-day-old fetal liver strongly suggesting that the enzyme detected in vitro was really active in vivo. This further supports the theory that secretion from the cell is also immature. The known deficiency of UDP-glucose dehydrogenase in fetal and neonatal rat liver could lead to decreased intracellular concentrations of UDP-glucuronic acid and possibly to increased concentrations of UDP-glucose. However, no glucosides were present in the fetal hepatocytes.     

放射测定胎鼠肝脏尿苷二磷酸葡萄糖醛酸转移酶1A1活性

目的探讨大鼠肝脏发育不成熟期葡萄糖醛酸转移酶1A1活性的发育规律,为研究新生儿期葡萄糖醛酸结合反应提供实验依据。方法用HeridrunMatern方法放射测定不同孕龄(孕17～19d各5只)及出生后不同日龄(生后1～5d各10只,生后2周的5只)大鼠的肝脏葡萄糖醛酸转移酶1A1活性。结果大鼠肝脏在孕17～19dUGT1A1活性较低,而且增长幅度小,孕19d酶的活性占成熟鼠活性的6.7%。生后1～2d时增长幅度很大,生后5d基本达成熟鼠水平,占成熟鼠活性的88.1%。将孕17d、孕19d、生后1d、成熟鼠这4组UGT1A1活性进行统计学检验,具有统计学意义。结论不成熟大鼠肝脏葡萄糖醛酸转移酶1A1活性很低,导致此期的胆红素葡萄糖醛酸结合反应水平低下。     

The role of lactate as an energy substrate for the brain during the early neonatal period

The role played by lactate as an energy substrate for the newborn rat during the early neonatal period was studied. Plasma lactate is mostly removed within the first 2 h after delivery, i.e. during the presuckling period. Lactate removal was enhanced by hyperoxia but strongly inhibited by hypoxia, showing a direct correlation with blood oxygen concentrations. Lactate was not converted into glucose during the presuckling period, gluconeogenesis being insignificant in these circumstances; instead it was rapidly oxidized through the tricarboxylic acid cycle. Likewise, lactate was significantly oxidized by brain slices from newborns at birth. At physiological concentrations, lactate oxidation by brain slices was 10- and 3-fold higher than that of glucose and 3-hydroxybutyrate, respectively. In the same circumstances, lipogenesis de novo from lactate was 2- and 5-fold higher than from glucose and 3-hydroxybutyrate, respectively. The results suggest that lactate is the main metabolic fuel for the brain during the early neonatal period.     

Role of thyroid hormones in the normal and glucocorticosteroid hormone-induced evolution of carbamoylphosphate synthase (ammonia) and arginase activity in perinatal rat liver

Administration of thyroid hormones causes a dose-dependent increase in carbamoylphosphate synthase (ammonia) and arginase activities in fetal rat liver but not in neonatal rat liver. Simultaneous administration of thyroid and glucocorticosteroid hormones enhances enzyme accumulation still further in the fetus. When administered before birth, the relative potencies of T4 and reverse T3, compared to T3 are 20--25% and 1--20%, respectively. Both before and after birth, thyroid hormones enhance DNA content of the liver. Hypophysectomy of rat fetus reduces the carbamoylphosphate synthase activity level in hepatocytes to 30--40% of that in intact animals. Thyroid and glucocorticosteroid hormone administered individually to hypophysectomized animals stimulate enzyme activity 2- to 3-fold; and if administered simultaneously, 4- to 6-fold. Premature delivery with continuation of thyroid and/or glucocorticosteroid hormone treatment started before birth shows uninterrupted enzyme accumulation profiles. Delaying birth by progesterone treatment of the dam leads to uninterrupted but reduced rates of enzyme accumulation in hepatocytes.     

Development of brush border peptidases in human and rat small intestine during fetal and neonatal life

The cytosol peptidase activities hydrolyzing glycl-L-leucine and L-leucyl-glycine as well as the activities of the brush border peptidases (oligoaminopeptidase, aminopeptidase A, gamma-glutamyl-transpeptidase, dipeptidyl-aminopeptidase IV, and carboxypeptidase) are present in rat fetuses during the early differentiation of the intestine (17th to 19th days of fetal life); they increase then at a different rate, reaching a maximum at various times, in the second and third wk after birth, and then decrease to the adult values during the first month of postnatal life. Only the oligoaminopeptidase activity increases steadily after birth, reaching maximal activity in the last decade of the first month. In human fetuses aged between 8 and 22 wk, the gamma-glutamyltranspeptidase was the only brush border peptidase found to be higher than in adults and children. On the other hand, the aminopeptidase A is remarkably reduced. The dipeptidylaminopeptidase IV and the carboxypeptidase are already at adult level in the youngest fetuses, and the oligoaminopeptidase increases during the period of fetal life studied; at the end of this period, the enzyme activity does not differ from the values found in children and adults. The small intestine of the term and preterm newborn should, therefore be able, with some possible exceptions, to efficiently digest peptides.     

Postnatal changes in carbamylphosphate synthetase-I and ornithine transcarbamylase activities after normal birth, premature delivery and prolonged gestation in rat liver: effects of actinomycin D and glucose.

The development of two urea cycle enzymes, carbamylphosphate synthetase-I and ornithine transcarbamylase was examined in neonatal rat liver. Normal birth on day 21.5 caused a marked increase of both activities as early as 4 h of extrauterine life. That increase occurred later in newborns delivered by cesarian section on day 21.5, but they exhibited a greater hepatic urea level. Premature delivery on day 20.5 caused a marked increase of both activities and hepatic urea level while prolonged gestation abolished these increases. The postnatal increase in both activities and in hepatic urea level was therefore dependent on a factor associated with birth. The in vivo administration of actinomycin D (2 microgram) at birth did not abolish the postnatal increase of both activities. Moreover, the administration of glucose (25 mg every 2 h) to newborns delivered by cesarian section on day 21.5 abolished the postnatal increase of ornithine transcarbamylase activity and hepatic urea level 23 h later. It seems that the transient hypoglycemia and appearance of gluconeogenesis at birth were the physiological mechanisms involved in the postnatal induction of ornithine transcarbamylase activity.     

Characteristic morphology of the constricted fetal ductus arteriosus following maternal administration of indomethacin

Indomethacin 10 mg/kg was administered to the maternal rat on the 21st day of pregnancy, and the fetal and neonatal ductus arteriosus were studied using the rapid whole-body freezing technique. The sagittal section of the frozen thorax disclosed characteristic localized constriction at the aortic end of the fetal ductus at 24 h after administration of indomethacin. Proximal dilatation of that fetal ductus persisted for more than 4 h after birth, and disappeared gradually. Shortening of the ductal length was associated with both intrauterine constriction by indomethacin in experimental rats and neonatal physiologic constriction of control rats, but significantly greater shortening was seen with intrauterine constriction.     

Maternal caffeine ingestion increases the tyrosine level in neonatal rat cerebrum

The cerebral free amino acids in neonatal rats, from dams given 0.04% caffeine in the drinking fluid ad libitum before and/or during pregnancy throughout the lactational period, were examined on days 1, 5 and 10. Significantly reduced cerebral weight was observed on day 1 with a mean caffeine level of 7 micrograms/g wet weight. The tyrosine concentration in the cerebrum, but not that in the liver, was increased on days 1 and 5 with approximate mean caffeine levels of above 1.5-2.0 micrograms/g wet weight. The tyrosine level showed a positive correlation with the caffeine level in neonatal cerebrum only on day 1 in the group with caffeine ingestion after pregnancy. There was no significant increase in the fetal cerebral concentration of MOPEG-SO4 on day 5 with maternal caffeine. These results suggest that maternal caffeine disturbs the neonatal cerebrum through tyrosine and tyrosine hydroxylase, and then produces behavioral abnormalities in developing rats.     

Ontogeny of cell type-specific enzyme reactivities in kidney collecting ducts

Highly specific antibodies against vital enzymes of the collecting ducts were used to study the appearance of cell type specific enzyme profiles in developing rat kidneys. (Na+K)-ATPase, the abundant enzyme of principal cells, could be detected early in utero in most collecting duct cells. However, the characteristic basolateral polarization of this enzyme did not appear until the first hours after birth. After this, the relative amount of (Na+K)-ATPase immunoreactive cells along collecting ducts decreased steadily, to reach the amount found in adult rat kidneys by the 30th postnatal day. Carbonic anhydrase immunoreactivity characteristic for intercalated cells was not detectable in fetal kidneys, but appeared soon after birth, with steadily increasing numbers of cells that were positive. Interestingly, immunoreactive band 3 glycoprotein (anion channel protein of erythrocytes) did not appear until the 5th day of life, with only a slowly increasing number of cells positive for this probe. These results, showing the sequential appearance of cell type-specific enzyme reactivities along collecting ducts, likely reflect a similar pattern of functional development of the respective main cell types. These results may provide an explanation for physiologic neonatal acidosis, as the enzyme profile associated with proton secretion was seen to appear slowly during the first weeks of life in a distinct manner.     

Postnatal development of plasma-lipid-clearing enzymes (lipoprotein lipase, hepatic lipase and lecithin:cholesterol acyl transferase) and lipid profiles in suckling rats.

We examined the activity of plasma circulating lipoprotein lipase and hepatic lipase, lecithin:cholesterol acyl transferase (LCAT), as well as lipid profiles in Sprague-Dawley rats from 1 day until 29 days of age. Plasma lipoprotein lipase activity peaked between ages 5 and 15 days and decreased after weaning, while plasma hepatic lipase activity remained constantly low during the suckling period and increased after weaning. No statistically significant difference in LCAT activity was seen from birth until weaning. Plasma triglycerides, as well as free fatty acids, decreased significantly after birth. Total plasma cholesterol increased during the suckling period and decreased after weaning. HDL cholesterol increased after the first 10 days of life, and free cholesterol remained constant after an initial decrease from birth to the 5th day of life. In conclusion, the enzymes associated with the metabolism of triglycerides, cholesterols and phospholipids are well developed in the rat shortly after birth.     

Development of enzymes of energy metabolism in rat heart

The behavior of several enzymes was studied during rat heart development (4 days before birth to adult stage). Hexokinase has its highest activity during the fetal period; it decreases at birth and remains with low activity in the adult. The alpha-glycerophosphate dehydrogenase and alpha-glycerophosphate oxidase profiles are similar up to the 15th day of development. From there onwards, both profiles diverge, the cytoplasmic activity increasing 3-fold, while the mitochondrial activity remains unchanged. The developmental profiles of the malate dehydrogenases are almost parallel. The development of citrate synthase and succinate dehydrogenase results in a 2- to 4-fold increase in their activities. However, ATPase increases dramatically (20-fold) over the same period. With respect to the enzymes of the adenine nucleotide metabolism, adenylate kinase is fully expressed throughout all ages examined, showing no variation during development. AMP deaminase and creatine kinase increase during development, the cytoplasmic creatine kinase reaching a high level at birth whereas the increases of the mitochondrial enzymes take place gradually during development.     

Development of enzymes of glycerol metabolism in human fetal liver

The activities of three key enzymes of glycerol metabolism were measured in liver samples from 37 human fetuses ranging in gestational age from 18 weeks to term, from neonates (1-3 days) and from infants to 2 years. Glycerol kinase specific activity was constant throughout the period of fetal development examined, and was comparable to that measured in neonates and infants. However, the subcellular distribution of the activity changed markedly, being predominantly particulate in fetal samples and cytoplasmic in postnatal samples. The particulate activity had an elevated Km for glycerol. Cytoplasmic glycerol-3-phosphate dehydrogenase activity was very low in the fetal period, and then rose to adult levels during infancy. There were no kinetic differences between the fetal and postnatal activities. Mitochondrial glycerol-3-phosphate dehydrogenase activity rose somewhat after birth to near adult levels. The data indicate that glycerol can be metabolized by human fetal, neonatal and infant liver.     

The development of antioxidant enzymatic defense in the perinatal rat lung: activities of superoxide dismutase, glutathione peroxidase, and catalase

This report describes the development of superoxide dismutase, glutathione peroxidase, and catalase activities in fetal (days 16-22) and neonatal (day 2 postpartum) lungs of normal rats. Each of the enzymes showed an individual pattern of development in the perinatal period. Glutathione peroxidase activity increased by 135% (p less than 0.001) during the last 3 days before birth, catalase activity by 105% (p less than 0.01) during the first 2 postnatal days, and the activity of superoxide dismutase by 52% (p less than 0.05) from gestational day 19 to 2 days after birth. Contamination by superoxide dismutase from blood in the lung samples accounted for less than 2% of the activity. In contrast, not less than 10-30% of glutathione peroxidase and catalase originated from the blood; and corrections were made for this source of error in each sample.