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Biomedical subjects

F J Suchy

Publications and source records attributed to F J Suchy.

At least 73 records · Page 4Linked to original sources
PubMed1987

Characterization of hepatic epidermal growth factor receptors in the developing rat.

Binding of 125I-labeled epidermal growth factor (EGF) was characterized in basolateral plasma membranes prepared from the livers of 21-day gestation fetuses, 14-day-old sucklings and adult Sprague-Dawley rats using a self-generating Percoll gradient method. The membrane preparations employed have been previously assayed in terms of plasma membrane protein yield, enrichment of various marker enzymes and sodium-dependent bile acid and amino acid transport. 125I-EGF binding was saturable and time and temperature dependent. Equilibrium analyses showed that the suckling period is characterized by a marked decrease in overall hepatic EGF binding capacity (460 +/- 50 fmol/mg protein) compared to either the fetal period (1290 +/- 160 fmol/mg) or to adults of either sex (males = 1540 +/- 230, females 1010 +/- 130 fmol/mg). Treatment of the suckling rat with parenteral EGF resulted in a 78% reduction in the observed binding capacity when assessed 2 h after growth factor administration. Comparison of binding affinities revealed no significant difference between the suckling and adult preparations (Kd = 0.40 +/- 0.03 vs. 0.39 +/- 0.02 nM, respectively); however, both preparations differed significantly from the fetal group which exhibited a decreased affinity of binding with a higher overall dissociation constant (Kd = 0.68 +/- 0.06 nM). Thus, it appears that major ontogenetic changes occur in the rat hepatic ligand/receptor system for epidermal growth factor. These changes are discussed in the context of transitional events in mammalian development such as birth and weaning.

Animals↗
PubMed1987

Determinants of bile formation during development: ontogeny of hepatic bile acid metabolism and transport.

The studies cited in this brief review stress that the development of hepatic transport processes is extraordinarily complex. Important changes in hepatic morphology and synthetic capacity are required before maturation of membrane carriers for bile acids. Transport systems at both poles of the hepatocyte develop independently. An increase in bile acid synthesis at several stages during the development appears to be an ontogenic event that is programmed to occur in concert with functional maturation of the enterohepatic circulation. Expression of specific membrane transporters for bile acids can be observed in fetal liver and postnatal ileum during periods of expansion of the bile acid pool. It is likely that specific defects, such as congenitally absent or defective bile acid transport proteins, will eventually be discovered in rare patients with undefined cholestatic syndromes. The absence of active ileal bile acid transport has recently been demonstrated in several children with congenital bile acid malabsorption. Whether bile acids can actually induce or regulate production of their own carriers during development has not been determined, but an increase in bile acid pool through feeding of exogenous bile acid has been shown to stimulate an increase in plasma membrane carriers for bile acids in adult rat liver. Thus, a number of factors, including available driving forces for transport, bile acid pool size and composition, effectiveness of intracellular compartmentation and transfer, and the function of membrane carriers, can all contribute to low rates of bile flow and bile acid secretion, depending on the stage of development.

Animals↗
PubMed1987

Hepatic taurine transport: a Na+-dependent carrier on the basolateral plasma membrane.

Highly purified rat basolateral liver plasma membrane vesicles were used to examine the mechanism and the driving forces for hepatic uptake of the beta-amino acid, taurine. An inwardly directed 100 mM NaCl gradient stimulated the initial rate of taurine uptake and energized a transient twofold accumulation of taurine above equilibrium ("overshoot"). In contrast, uptake was slower and no overshoot was detected in the presence of a KCl gradient. A negative intravesicular electrical potential generated by the presence of permeant anions or an outwardly directed K+ gradient with valinomycin increased Na+-stimulated taurine uptake. External Cl- stimulated Na+-dependent taurine uptake independent of effects on the transmembrane electrical potential difference. Na+-dependent taurine uptake showed a sigmoidal dependence on extravesicular Na+ concentration, suggesting multiple Na+ ions are involved in the translocation of each taurine molecule. Na+-dependent taurine uptake demonstrated Michaelis-Menten kinetics with a maximum velocity of 0.537 nmol.mg protein-1.min-1 and an apparent Km of 174 microM. [3H]taurine uptake was inhibited by the presence of excess unlabeled taurine, beta-alanine, or hypotaurine but not by L-glutamine or L-alanine. In summary, using basolateral liver plasma membrane vesicles, we have shown that hepatic uptake of taurine occurs by a carrier-mediated, secondary active transport process specific for beta-amino acids. Uptake is electrogenic, stimulated by external Cl-, and requires multiple Na+ ions for the translocation of each taurine molecule.

Amino Acids↗
PubMed1987

Absence of an acinar gradient for bile acid uptake in developing rat liver.

We studied the acinar distribution for uptake of the bile acid analogue [125I]-cholylglycyltyrosine in livers from adult and 14-day-old suckling rats. Portal and peripheral (systemic) serum bile acid concentrations were also measured by combined gas chromatography-mass spectrometry as an independent index of hepatic bile acid clearance from portal blood. Utilizing light microscopic autoradiography, a steep, decreasing portal to centrilobular gradient for cholylglycyltyrosine uptake was noted in adult rat liver. In contrast, there was no lobular gradient for cholylglycyltyrosine uptake visible in the 14-day-rat liver; all hepatocytes within the acinus contained a similar number of silver grains. Portal vein total bile acid concentrations were significantly higher in serum of adult compared to 14-day-old rats. In contrast, bile acid concentrations were 10-fold higher in the peripheral serum of developing versus adult rats. The peripheral to portal serum bile acid concentration ratio was 0.23 in the adult and 6.48 in the 14-day-old rat. We conclude that the entire hepatic lobule participates in the uptake of bile acids in the 14-day-old rat even under the basal conditions of this study. The normal "reserve" function of centrilobular hepatocytes is not sufficient to compensate for the decreased transport capacity of the developing liver with the result that increased concentrations of bile acids enter and accumulate in the systemic circulation.

Aging↗
PubMed1986

Ontogeny of bile acid transport in brush border membrane vesicles from rat ileum.

We studied the postnatal development of bile acid transport in rat ileum, using brush border membrane vesicles prepared by a Ca2+ precipitation method. Membrane vesicles from developing (day 14-21) and adult Sprague-Dawley rats were enriched to a similar degree in brush border membrane marker enzyme activities (sucrase or lactase) compared with homogenate. Uptake of 25 microM [3H]taurocholate by adult membrane vesicles was markedly accelerated in the presence of an inwardly directed 100 mM Na+ gradient compared with a K+ gradient, and there was a transient intravesicular accumulation of isotope above equilibrium ("overshoot"). In contrast, at 14 and 16 days of age there was no difference in taurocholate uptake in the presence of a Na+ or a K+ gradient, and uptake was not saturable. The integrity of the vesicle preparation from 14- and 16-day-old rats was confirmed by the demonstration of Na+-dependent uphill transport of 100 microM L-[3H]alanine. Stimulation of taurocholate uptake by a Na+ compared with a K+ gradient ("sodium effect") was first observed at age 17 days, but an overshoot was not present until 18 days of age. The initial rate of Na+-dependent taurocholate (25 microM) uptake increased sixfold between 17 and 21 days of age (24.36 +/- 6.11 to 148.59 +/- 8.56 pmol X mg-1 protein X 5 s-1). Absent or decreased Na+-dependent taurocholate uptake was not due to increased permeability or "leakiness" of vesicles from younger animals to Na+. Ileal brush border membrane vesicles demonstrated saturable kinetics at 21 days, but the Vmax was significantly lower (10.15 +/- 0.44 vs. 13.42 +/- 0.59 nmol X mg-1 protein X min -1, p less than 0.001) and the apparent Km higher (130.6 +/- 18.9 vs. 70.1 +/- 12.6 microM, p less than 0.007) than the adult. We conclude that (a) saturable, Na+-bile acid coupled transport is absent in rat ileum throughout most of the suckling period and (b) kinetic analysis suggests that maturation occurs near weaning, primarily through an increase in functional bile acid carriers within the ileal brush border membrane.

Animals↗
PubMed1986

Pustular pyoderma gangrenosum associated with ulcerative colitis in childhood. Report of two cases and review of the literature.

Pyoderma gangrenosum is a cutaneous disorder associated with systemic diseases such as ulcerative colitis, Crohn's disease, rheumatoid arthritis, and blood dyscrasias. We are reporting two cases of pustular pyoderma gangrenosum associated with ulcerative colitis. One patient had inactive bowel disease when she developed her third episode of pustules, erosions, and nodules on the left leg. The other patient exhibited a widespread painful vesiculopustular eruption that coincided with the onset of her colitis. Both patients presented with pustules as the primary manifestation of their pyoderma gangrenosum. Histologic examination of skin from both patients revealed an acute perifollicular inflammation. Pyoderma gangrenosum should be considered in the differential diagnosis of pustular disorders in children with underlying conditions such as ulcerative colitis.

Abscess↗
PubMed1986

Taurocholate transport and Na+-K+-ATPase activity in fetal and neonatal rat liver plasma membrane vesicles.

The ontogenesis of Na+-K+-ATPase activity and Na+-taurocholate cotransport was studied in basolateral plasma membrane vesicles from fetal and neonatal rat liver. Membrane vesicles from each age group were 30-fold enriched in the basolateral marker enzyme Na+-K+-ATPase, 4- to 7-fold enriched in the bile canalicular membrane marker enzymes alkaline phosphatase and Mg2+ ATPase, and not significantly enriched in activities of marker enzymes for intracellular organelles. Na+-K+-ATPase activity was significantly lower in basolateral membranes from late fetal (day 21-22) and neonatal (day 1) rat liver. Kinetic analysis of Na+-K+-ATPase activity at various concentrations of ATP revealed that the maximum velocity of enzyme reaction (Vmax) for Na+-K+-ATPase was 70 and 90% of adult activity in the fetus and the neonate, respectively. The ATP Km was significantly lower in the neonate than the adult, suggesting a higher affinity of the neonatal enzyme for ATP. In contrast to the early maturation of Na+-K+-ATPase, transport of taurocholate was markedly lower in both fetal and neonatal vesicles compared with the adult. Taurocholate uptake on day 19 of gestation did not differ in the presence of a Na+ or K+ gradient, and uphill transport, as indicated by an overshoot, did not occur. On day 20 taurocholate uptake was stimulated by a Na+ compared with a K+ gradient, and accumulation of isotope above equilibrium was demonstrated. Na+-dependent transport of taurocholate by late fetal (day 22) and neonatal vesicles was saturable but the Vmax at each age was significantly lower and the apparent Km higher in developing compared with adult membrane vesicles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Taurocholate transport by basolateral plasma membrane vesicles isolated from developing rat liver.

Taurocholate transport was characterized in basolateral plasma membrane vesicles prepared from the livers of 14-day-old Sprague-Dawley rats using a self-generating Percoll gradient method. Liver plasma membrane protein yield, intravesicular volume, and enrichments of various marker enzymes were similar to those obtained for vesicles from adult rat liver. The basolateral marker enzyme Na+-K+-ATPase was enriched 26-fold in the suckling rat basolateral membrane fraction while the bile canalicular marker enzymes alkaline phosphatase and Mg2+-ATPase were enriched only 3- and 5-fold, respectively. The activities of marker enzymes for endoplasmic reticulum, mitochondria, or lysosomes were not enriched compared with homogenate. In the presence of an inwardly directed 100 mM Na+ gradient, vesicle accumulation of taurocholate transiently reached a concentration 1.5- to 2-fold higher than that at equilibrium ("overshoot") in suckling and adult membrane vesicles, but the initial rate of taurocholate entry and peak intravesicular accumulation were markedly decreased in suckling compared with adult membrane vesicles. In the presence of an inwardly directed 100 mM K+ gradient, the rate of uptake was slower, and no overshoot occurred in either suckling or adult rat vesicles. The decreased rate of Na+-coupled taurocholate uptake by membrane vesicles from suckling rat liver could not be explained on the basis of more rapid dissipation of the transmembrane Na+ gradient. Kinetic studies demonstrated saturable, Na+-dependent taurocholate uptake for both suckling and adult vesicles. However, the Vmax for taurocholate uptake in suckling rat vesicles was less than half of the adult rate (2.46 +/- 0.13 vs. 5.25 +/- 0.22 nmol X mg prot-1 X min-1, respectively, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Ontogeny of hepatic bile acid conjugation in the rat.

We studied the postnatal development of hepatic bile acid conjugation in the rat. Overall conjugating activity (homogenate assay) and the activity of the individual enzymes involved in the two step conjugation reaction (coenzyme A-bile acid thioester formation by microsomal cholyl-CoA ligase and amino acid transfer to this intermediate mediated by cytosolic cholyl-CoA:taurine N-acyltransferase were measured on days 1, 7, 14, 21, and 56 of life. Cholic acid conjugation was significantly lower in the suckling rat on days 1, 7, and 14 compared to the adult rat on day 56. At weaning (21 days) there was a marked increase in homogenate activity to a level higher than at 56 days. This peak in conjugating activity could be precociously induced on day 14 by cortisone acetate injection on days 10 through 13. Both cholyl-CoA ligase and cholyl-CoA:taurine N-acyltransferase activities were significantly lower during the first 14 days of life in comparison with 56 days. At 21 days of age there was a sharp increase in cholyl-CoA ligase activity to 1.5 times the activity in the adult; however, cholyl-CoA:taurine N-acyltransferase activity remained less than half of that found in the adult. We conclude that 1) cholic acid conjugation, as assessed by determination of either total conjugating activity or by the individual enzymatic steps, is decreased in the suckling rat; 2) the peak in conjugating activity noted at weaning may be mediated by the hormonal milieu, and 3) cholyl-CoA ligase activity closely parallels the increase in total activity and appears to be rate-limiting during development.

Acyltransferases↗
PubMed1985

Amino acids are potent inhibitors of bile acid uptake by liver plasma membrane vesicles isolated from suckling rats.

We studied the effects of amino acids which undergo Na+-coupled cotransport on taurocholate uptake by basolateral liver plasma membrane vesicles prepared from 14-day-old rats. At concentrations similar to the total concentration of Na-dependent amino acids measured in portal blood, the Na+-dependent amino acids, L-alanine and L-glutamine, reduced the initial velocity of Na+-dependent taurocholate uptake and impaired uphill transport of the bile acid. In contrast, the Na+-independent amino acid, 2-aminobicyclo(2,2,1)heptane-2-carboxylic acid, did not affect taurocholate uptake. The inhibitory effect of Na+-dependent amino acids on taurocholate uptake was dose dependent. Taurocholate uptake was electroneutral and the inhibition of bile acid uptake by L-glutamine was not affected by the electrical potential. In the absence of a sodium gradient, but with equal intravesicular and extravesicular sodium concentrations, L-glutamine did not inhibit bile acid uptake. With an inwardly directed Na+ gradient, 22Na+ uptake (8 s) was 27% higher in the presence of L-glutamine (5 mM) than without L-glutamine. Kinetic analysis showed that L-glutamine (5 mM) decreased the maximum velocity of Na+-dependent taurocholate uptake to 59% of control (1.62 +/- 0.20 versus 2.73 +/- 0.30 nmol . mg-1 protein . min-1; p less than 0.002), but had no effect on the taurocholate Km (91.7 +/- 26.4 versus 97.1 +/- 25.4 microM). We conclude that physiologic concentrations of Na+-dependent amino acids markedly inhibit taurocholate uptake by membrane vesicles from 14-day rat livers.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1984

Possible dissociation between insulin binding and insulin action in isolated fetal rat hepatocytes.

To directly examine the relationship between insulin receptors and insulin action in fetal tissue, we compared insulin receptor characteristics and insulin-mediated 14C-glucose incorporation into glycogen, as well as glycogen synthase activity, in freshly isolated hepatocytes from 21-day fetal (F) and adult (A) rats. Viability of hepatocytes was documented by trypan blue exclusion (greater than 90%), time-dependent 14C-leucine incorporation into protein, and dose-related incorporation of glucose into glycogen. Percent specific binding of 125I-insulin per unit protein was significantly higher in F than A liver plasma membranes (32.2 +/- 0.3 versus 18 +/- 2.4; P less than 0.01) and Scatchard plots revealed twice the number of receptors in F. Similarly, receptor number per cell surface area was threefold higher in F than in A (150 versus 50 sites/micron2). At a fixed medium glucose concentration of 11.2 mM, insulin stimulated 14C-glucose incorporation into glycogen in a dose-related manner in A with an apparent Km of 1.0 ng/ml and Vmax at 5-10 ng/ml corresponding to 30-40% of total receptor occupancy; no effect was obtained in F with insulin up to 100 ng/ml. Net glucose incorporation into glycogen (nmol/10(6) cells/h) increased progressively with increasing medium glucose concentrations ranging from 1.4 to 27.8 mM; incorporation by F was significantly greater than by A at each glucose concentration. However, whereas insulin at 100 ng/ml significantly augmented net glucose incorporation at each glucose concentration in A, no effect of insulin was apparent in F.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1984

Bile salt sulfotransferase: alterations during maturation and non-inducibility during substrate ingestion.

Development of the capacity for hepatic biotransformation of potentially toxic, endogenous compounds such as lithocholate may be dependent on induction by substrate or hormonal modulation. Our aim was to observe the ontogeny of hepatic sulfotransferase (ST) activity, a presumed detoxification pathway, and to determine the effect of substrate ingestion and cortisone administration on ST activity. Pregnant rats were fed a standard chow diet containing lithocholate; the maternal diet was continued during the suckling and weaning phase of the pups. Liver cytosol and serum were obtained from dams and from pups at weekly intervals from fetal life through 4 weeks of age. In controls, there was a progressive increase in hepatic ST activity from 6.2 +/- 2.9 pmol/mg protein per min, (mean +/- SEM) in fetal liver, 18.1 +/- 3.9 at 1 week, an 33.6 +/- 7.2 at 2 weeks to a peak of 56.4 +/- 11.8 at 3 weeks of age. In female rats older than 4 weeks of age, ST activity in hepatic cytosol was threefold higher than in males. There was a decline to adult levels (9.2 +/- 2.4 in males and 39.4 +/- 4.3 in females) at 56 days of life. Cortisone acetate administration had no effect on enzyme activity in pups except those 3 weeks old or older in which there was a precocious decrease in enzyme activity to adult levels. The administration of lithocholate caused a dose-related postnatal alteration of intrahepatic bile ducts manifest as cholangitis with ductular proliferation; hepatocytes were spared.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1983

Grade I Reye's syndrome. A frequent cause of vomiting and liver dysfunction after varicella and upper-respiratory-tract infection.

In a one-year prospective study we assessed the incidence of Reye's syndrome in children presenting with the acute onset of vomiting after a prodromal upper-respiratory-tract infection or varicella, and with serum alanine or aspartate aminotransferase levels at least three times higher than normal, and a paucity of neurologic findings. Of 25 patients meeting the above criteria, 19 had liver biopsies yielding adequate tissue for diagnostic purposes. Biopsy specimens from 14 of these 19 patients (74 per cent) were diagnostic of Reye's syndrome, according to rigorous light-microscopical, histochemical, and ultrastructural criteria. None of the biopsy specimens contained evidence of other acute pathologic processes, including hepatitis. A wide spectrum of mitochondrial alterations existed at the ultrastructural level, ranging from mild to severe lesions that were indistinguishable from those seen in comatose patients with Reye's syndrome. Our findings suggest that the clinical complex of vomiting, hepatic dysfunction, and minimal neurologic impairment after varicella or an upper-respiratory-tract infection usually represents Reye's syndrome. This syndrome occurs more frequently than previously recognized.

Adolescent↗
PubMed1983

Intracellular bile acid transport in rat liver as visualized by electron microscope autoradiography using a bile acid analogue.

The role of hepatocyte organelles in the intracellular transport and secretion of conjugated bile acids has not been defined. Therefore we studied the transport and observed the subcellular localization of the bile acid analogue 125I-cholylglycyltyrosine by electron microscope autoradiography to further understand the possible compartmentation of bile acids within the hepatocyte. 125I-cholylglycyltyrosine, which retains a net negative charge, exhibited transport properties similar to native bile acids. After portal vein injection, the compound was recovered intact from bile, and the pattern of excretion paralleled that of [14C]cholylglycine. In addition, cholylglycyltyrosine uptake by isolated hepatocytes was sodium dependent. For autoradiography the analogue was injected into the portal vein, and the liver was perfusion fixed after 30 or 300 s. Light microscope autoradiography performed 30 s after isotope injection demonstrated a steep periportal-to-centrilobular gradient for 125I-cholylglycyltyrosine uptake. At 30 s quantitative grain analysis of electron microscope autoradiographs showed predominant labeling of the plasma membrane and the smooth endoplasmic reticulum (SER). The grain distribution over the region of the plasma membrane decreased from 15% at 30 s to 7% by 300 s and was associated with a sevenfold increase in labeling of the Golgi apparatus and a sixfold increase in labeling of the pericanalicular region. Grain distribution over the SER at 300 s was the same as that noted at 30 s. The hypothesis is presented that bile acids move from the sinusoidal plasma membrane to bile via a pathway that includes the SER and Golgi apparatus.

Animals↗