Kinetics and uptake in vivo of oxidatively modified lymph chylomicrons

1995 ◽  
Vol 268 (4) ◽  
pp. G709-G716
Author(s):  
Y. Umeda ◽  
T. G. Redgrave ◽  
B. C. Mortimer ◽  
J. C. Mamo
Keyword(s):  
Fish Oil ◽  
Corn Oil ◽  
Reticuloendothelial System ◽  
Hepatic Uptake ◽  
Slow Phase ◽  
Liver Uptake ◽  
Rapid Phase ◽  
Oxidatively Modified ◽  
Oil Particles

The metabolism of oxidized chylomicrons (ox-CMs) was investigated in vivo. CMs from rats fed corn, linseed, or fish oil were oxidized by incubation with 2,2'-azobis(2-amidinopropane)hydrochloride (AAPH) or sodium hypochlorite (NaOCl). Oxidized CMs had a rapid phase of clearance, followed by a slow phase. Clearance of ox-CMs was decreased for corn oil but increased for linseed and fish oil particles. Differences in rats of uptake between CM types or treatment were independent of the rate of remnant formation, but were instead a consequence of decreased clearance. A greater triglyceride-to-cholesteryl ester ratio in liver suggested that there was less lipolysis of ox-CM triglyceride prior to uptake. Hepatic uptake of ox-CMs was decreased, whereas there was increased uptake in spleen. However, the uptake by Kupffer cells of ox-CMs was 43% of total liver uptake after AAPH treatment and 59% after NaOCl treatment, compared with 21% for control CMs. Collectively, our data show that oxidation can have differential effects on the rate of clearance of CMs and that ox-CMs are preferentially cleared by the reticuloendothelial system.

scholarly journals Capacity of human serum to depolymerize actin filaments

Blood ◽  
1987 ◽  
Vol 70 (2) ◽  
pp. 524-530
Author(s):  
PA Janmey ◽  
SE Lind
Keyword(s):  
Human Serum ◽  
Actin Filaments ◽  
Serum Proteins ◽  
Normal Serum ◽  
Slow Phase ◽  
Rapid Phase ◽  
Plasma Gelsolin ◽  
Preferential Formation

Human blood depolymerizes filamentous (F-)actin. The interaction of actin filaments and monomers with human serum was studied by following the kinetics and extent of the depolymerization of pyrene-labeled F- actin and by analysis of serum proteins adhering to immobilized actin monomers. In physiologic Ca2+ concentrations, the depolymerization of F- actin proceeds in two stages: a rapid phase, attributed to direct severing of filaments by plasma gelsolin, and a slow phase attributed to the binding of actin monomers to vitamin D-binding protein (DBP). Without Ca2+, only the slow phase is observed. Human serum can completely depolymerize 10 to 18 mumol/L of actin, of which approximately 5 mumol/L occurs rapidly. Depolymerization can be accounted for by the normal serum concentrations of gelsolin and DBP. Fibrin(ogen) and fibronectin, which bind actin in vitro, do not contribute to the kinetics or extent of its depolymerization. Affinity chromatography and functional assays for the presence of gelsolin-actin complexes show that addition of G-actin to serum results in preferential formation of actin-DBP complexes, but that addition of F- actin to serum produces both gelsolin-actin complexes and DBP-actin complexes. The distinctive binding of actin monomers and polymers to these two serum proteins suggests a means by which their coordinated actions are maximized in vivo, from the standpoint of depolymerizing filaments and clearing monomers from the circulation.

scholarly journals Preclinical Evaluation of [18F]LCATD as a PET Tracer to Study Drug-Drug Interactions Caused by Inhibition of Hepatic Transporters

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Andrea Testa ◽  
Sergio Dall’Angelo ◽  
Marco Mingarelli ◽  
Andrea Augello ◽  
Lutz Schweiger ◽  
...  
Keyword(s):  
Drug Interactions ◽  
Lithocholic Acid ◽  
Hepatic Uptake ◽  
Drug Induced ◽  
Liver Uptake ◽  
Rifamycin Sv ◽  
Pet Tracer ◽  
Hepatic Transporters ◽  
Uptake Transporters

The bile acid analogue [18F]LCATD (LithoCholic Acid Triazole Derivative) is transported in vitro by hepatic uptake transporters such as OATP1B1 and NTCP and efflux transporter BSEP. In this in vivo “proof of principle” study, we tested if [18F]LCATD may be used to evaluate drug-drug interactions (DDIs) caused by inhibition of liver transporters. Hepatic clearance of [18F]LCATD in rats was significantly modified upon coadministration of rifamycin SV or sodium fusidate, which are known to inhibit clinically relevant uptake transporters (OATP1B1, NTCP) and canalicular hepatic transporters (BSEP) in humans. Treatment with rifamycin SV (total dose 62.5 mg·Kg−1) reduced the maximum radioactivity of [18F]LCATD recorded in the liver from 14.2 ± 0.8% to 10.2 ± 0.9% and delayed t_max by 90 seconds relative to control rats. AUCliver 0–5 min, AUCbile 0–10 min and hepatic uptake clearance CLuptake,in vivo of rifamycin SV treated rats were significantly reduced, whereas AUCliver 0–30 min was higher than in control rats. Administration of sodium fusidate (30 mg·Kg−1) inhibited the liver uptake of [18F]LCATD, although to a lesser extent, reducing the maximum radioactivity in the liver to 11.5 ± 0.3%. These preliminary results indicate that [18F]LCATD may be a good candidate for future applications as an investigational tracer to evaluate altered hepatobiliary excretion as a result of drug-induced inhibition of hepatic transporters.

Comparison of the effects of dietary n−3 and n−6 polyunsaturated fatty acids on very-low-density lipoprotein secretion when delivered to hepatocytes in chylomicron remnants

2001 ◽  
Vol 357 (2) ◽  
pp. 481-487 ◽  
Author(s):  
Xiaozhong ZHENG ◽  
Michael AVELLA ◽  
Kathleen M. BOTHAM
Keyword(s):  
Fatty Acids ◽  
Polyunsaturated Fatty Acids ◽  
Fish Oil ◽  
Corn Oil ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Very Low Density Lipoprotein ◽  
Low Density ◽  
Chylomicron Remnants

The effects of chylomicron remnants enriched in n-3 or n-6 polyunsaturated fatty acids (derived from fish or corn oil respectively) on the secretion of very-low-density lipoprotein (VLDL) lipid and apolipoprotein B (apoB) by rat hepatocytes in culture was investigated. Remnants were prepared in vivo from chylomicrons obtained from rats given an oral dose of fish or corn oil and incubated with cultured hepatocytes for up to 16h. The medium was then removed and the secretion of cholesterol and triacylglycerol into the whole medium or the ρ < 1.050g/ml fraction during the following 7–24h was determined. After exposure of the cells to fish-oil as compared with corn-oil remnants, secretion of both cholesterol and triacylglycerol into the whole medium was decreased by 25–35%, and secretion into the ρ < 1.050g/ml fraction was decreased by 20–25%. In addition, the levels of apoB48 found in the ρ < 1.050g/ml fraction were significantly lower in cells treated with fish-oil rather than corn-oil remnants, although the levels of apoB100 remained unchanged. The expression of mRNA for apoB, as determined by reverse-transcriptase PCR, however, was not significantly changed after exposure of the cells to both types of remnants. These results demonstrate that the effects of dietary n-3 polyunsaturated fatty acids in depressing hepatic VLDL secretion occur directly when they are delivered to the liver from the intestine in chylomicron remnants, and that the secretion, but not the synthesis, of apoB is targeted.

Catabolism of Fibrinogen and its Derivatives

1977 ◽  
Vol 38 (04) ◽  
pp. 0809-0822 ◽  
Author(s):  
Laurence A. Sherman
Keyword(s):  
Experimental Data ◽  
Molecular Weight ◽  
Degradation Products ◽  
Reticuloendothelial System ◽  
Hepatic Uptake ◽  
Low Molecular Weight ◽  
Cell Membrane Binding ◽  
Relationship Of ◽  
The Relationship

SummaryAlthough the site and manner of normal catabolism of most of the fibrinogen pool is uncertain, certain pathways have been defined for various fibrinogen derivatives. Several organs, including the kidneys and reticuloendothelial system (RES) have been directly implicated as catabolic sites for various fibrinogen derivatives. The catabolic sites are not the same for different derivatives. These differences in catabolism are probably in part related to biochemical differences between fibrinogen and its various derivatives. Fibrinogen itself may be catabolized in endothelial cells, although little experimental data is available. RES uptake of intact fibrinogen does not occur, and removal of sialic acid does not result in the rapid hepatic uptake seen with other desialop rote ins. In contrast, a variety of studies have shown that fibrin is taken up by the RES by at least 2 mechanisms. The first is phagocytosis of microparticulate fibrin. The second involves a RES cell membrane binding of soluble fibrin which remains soluble in the blood, when complexed to fibrinogen or degradation products. Fibrinogen degradation products alone may in part also be cleared in the RES. Fragments D and E appear to be catabolized in the kidney, although both the intrarenal site of catabolism and the means of cellular uptake is unknown. It is clear that normally there is no urinary excretion of D and E. Another fibrinogen derivative, low molecular weight clottable fraction 1–8, is derived in vivo from intact fibrinogen. 1–8 is found normally in the blood and has a shorter t ½ than fibrinogen although much longer than D and E. While originally thought to be the result of limited plasmin degradation, 1–8 may be the result of another type of proteolysis. The sites of both 1–8 formation and degradation are unknown. Catabolism via fibrin, 1–8, or D and E appears to be only a small percent of normal turnover, albeit of much greater significance in disease. The relationship of these pathways to the as yet unknown catabolic site for the bulk of normal fibrinogen remains to be determined.

scholarly journals Capacity of human serum to depolymerize actin filaments

Blood ◽  
1987 ◽  
Vol 70 (2) ◽  
pp. 524-530 ◽  
Author(s):  
PA Janmey ◽  
SE Lind
Keyword(s):  
Human Serum ◽  
Actin Filaments ◽  
Serum Proteins ◽  
Normal Serum ◽  
Slow Phase ◽  
Rapid Phase ◽  
Plasma Gelsolin ◽  
Preferential Formation

Abstract Human blood depolymerizes filamentous (F-)actin. The interaction of actin filaments and monomers with human serum was studied by following the kinetics and extent of the depolymerization of pyrene-labeled F- actin and by analysis of serum proteins adhering to immobilized actin monomers. In physiologic Ca2+ concentrations, the depolymerization of F- actin proceeds in two stages: a rapid phase, attributed to direct severing of filaments by plasma gelsolin, and a slow phase attributed to the binding of actin monomers to vitamin D-binding protein (DBP). Without Ca2+, only the slow phase is observed. Human serum can completely depolymerize 10 to 18 mumol/L of actin, of which approximately 5 mumol/L occurs rapidly. Depolymerization can be accounted for by the normal serum concentrations of gelsolin and DBP. Fibrin(ogen) and fibronectin, which bind actin in vitro, do not contribute to the kinetics or extent of its depolymerization. Affinity chromatography and functional assays for the presence of gelsolin-actin complexes show that addition of G-actin to serum results in preferential formation of actin-DBP complexes, but that addition of F- actin to serum produces both gelsolin-actin complexes and DBP-actin complexes. The distinctive binding of actin monomers and polymers to these two serum proteins suggests a means by which their coordinated actions are maximized in vivo, from the standpoint of depolymerizing filaments and clearing monomers from the circulation.

scholarly journals Kinetics of removal of intravenous testosterone pulses in normal men

2010 ◽  
Vol 162 (4) ◽  
pp. 787-794 ◽  
Author(s):  
Johannes D Veldhuis ◽  
Daniel M Keenan ◽  
Peter Y Liu ◽  
Paul Y Takahashi
Keyword(s):  
Sampling Strategy ◽  
Free Testosterone ◽  
Slow Phase ◽  
Total Testosterone ◽  
Rapid Phase ◽  
Deconvolution Analysis ◽  
Normal Men ◽  
Frequent Sampling ◽  
Kinetics Of

BackgroundTestosterone is secreted into the bloodstream episodically, putatively distributing into total, bioavailable (bio) nonsex hormone-binding globulin (nonSHBG-bound), and free testosterone moieties. The kinetics of total, bio, and free testosterone pulses are unknown.DesignAdrenal and gonadal steroidogenesis was blocked pharmacologically, glucocorticoid was replaced, and testosterone was infused in pulses in four distinct doses in 14 healthy men under two different paradigms (a total of 220 testosterone pulses).MethodsTestosterone kinetics were assessed by deconvolution analysis of total, free, bioavailable, SHBG-bound, and albumin-bound testosterone concentration–time profiles.ResultsIndependently of testosterone dose or paradigm, rapid-phase half-lives (min) of total, free, bioavailable, SHBG-bound, and albumin-bound testosterone were comparable at 1.4±0.22 min (grand mean±s.e.m. of geometric means). Slow-phase testosterone half-lives were highest for SHBG-bound testosterone (32 min) and total testosterone (27 min) with the former exceeding that of free testosterone (18 min), bioavailable testosterone (14 min), and albumin-bound testosterone (18 min; P<0.001). Collective outcomes indicate that i) the rapid phase of testosterone disappearance from point sampling in the circulation is not explained by testosterone dose; ii) SHBG-bound testosterone and total testosterone kinetics are prolonged; and iii) the half-lives of bioavailable, albumin-bound, and free testosterone are short.ConclusionA frequent-sampling strategy comprising an experimental hormone clamp, estimation of hormone concentrations as bound and free moieties, mimicry of physiological pulses, and deconvolution analysis may have utility in estimating the in vivo kinetics of other hormones, substrates, and metabolites.

Vascular clearance and organ uptake of G- and F-actin in the rat

1993 ◽  
Vol 265 (6) ◽  
pp. G1071-G1081 ◽  
Author(s):  
A. J. Herrmannsdoerfer ◽  
G. T. Heeb ◽  
P. J. Feustel ◽  
J. E. Estes ◽  
C. J. Keenan ◽  
...  
Keyword(s):  
Kupffer Cells ◽  
Slow Component ◽  
Cell Uptake ◽  
Slow Phase ◽  
Organ Distribution ◽  
Rapid Phase ◽  
Time Constants ◽  
Clearance Kinetics ◽  
Two Phases

This study comparatively evaluated the kinetics of removal and organ distribution of circulating G- and F-actin. Both F- and G-actin were cleared in two phases (fast component with a t1/2 of 3-5 min and a slow component with a t1/2 of hours). There was no effect of dose on either the fast- or slow-compartment clearance kinetics at the doses tested (5-100 micrograms/100 g body wt). However, at the same challenging dose of F- and G-actin, more F-actin was removed during the rapid phase. Although the time constants (Tfast) for F- and G-actin removal from the vasculature during the initial rapid phase were the same, during the slow phase the time constants (Tslow) for removal of F-actin were less (P < 0.001) than that of G-actin. The fraction of F-actin removed during the rapid phase ranged from 33 to 63% and was significantly greater (P < 0.01) than the fraction of G-actin removed during this phase (10-33%). The liver was the main organ of localization, and autoradiographic studies of liver tissue demonstrated that G-actin monomers were removed by Kupffer cells, whereas F-actin was predominantly removed by hepatic sinusoidal endothelial cells. In vivo endotoxin activation of Kupffer cells enhanced the rate of G-actin removal and increased liver localization of G-actin but had no effect on F-actin removal. This further supports a role for Kupffer cells in the clearance of G-actin. These studies therefore demonstrate that F- and G-actin clearance mechanisms are different. G-actin removal, presumably mediated by its binding to vitamin D binding protein, is accomplished by Kupffer cells, whereas F-actin removal at the same doses is due mainly to hepatic endothelial cell uptake.

Clearance of Tissue Plasminogen Activator by Mannose and Galactose Receptors in the Liver

1990 ◽  
Vol 63 (01) ◽  
pp. 060-066 ◽  
Author(s):  
Bård Smedsrød ◽  
Monica Einarsson
Keyword(s):  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Hepatic Uptake ◽  
Uptake Mechanism ◽  
Total Size ◽  
Rapid Phase ◽  
Radioactive Label ◽  
Tissue Plasminogen ◽  
Clearance Kinetics

SummaryThe mechanism of uptake of radio-iodinated tissue plasminogen activator (125I-t-PA) was studied in rats. When trace amounts of 125I-t-PA were injected alone, the clearance followed a biphasic pattern in which 65% and 35% were cleared with α- and β-kinetics (t1/2 (α) = 0.6 min, and t1/2 (β) = 6.4 min), respectively. Coinjection with excess unlabelled t-PA or inannan changed the uptake kinetics to the muiiupliasic β-elimination pattern. Mannosylated albumin and ovalbumin, both of which bind to the hepatic mannose receptor, reduced the proportion of t-PA cleared with t1/2 (α) to 48% and 21%, respectively. A corresponding increase in the β-elimination ot t-PA was observed. The t1/2 (α) and t1/2 (β) were unchanged. Studies on the eleaiaucc of 125I-ovalbumin also showed a biphasic elimination with an initial rapid phase, t1/2 (α), accounting for only 39% of the clearance of ovalbumin, as compared to 65% in the case of t PA. Macromolecules with affinity for the galactose-receptor only, such as asialofetuin, or galactosylated albumin, did not significantly affect the clearance kinetics at the concentrations used. Asialoorosomucoid, which also carries galactosyl residues in the terminal position, reduced somewhat (from 65% to 48%) the proportion cleared with α-kinetics. Very high concentrations of galactose and N-acetyl-galactosamine, which are also known to compete for binding to the galactose receptor, lowered the proportion of t-PA cleared in the late β-phase (reduced from 35% to 26% with galactose and to 19% with N-acetyl-galactosamine).To determine the hepatocellular site of uptake of t-PA, the protein was conjugated with 125I-labelled tyramine cellobiose (125I-TC) and injected intravenously (i.v.). This adduct is nonbiodegradable, and is trapped intralysosomally after endocytosis. I.v. injection of 125I-TC-t-PA and subsequent isolation of the liver cells showed that the Kupffer cells (KC), liver endothelial cells (LEC) and parenchymal cells (PC) contained 11%, 44% and 45%, respectively, of the radioactive label recovered in liver (hepatic uptake 80% of injected dose). The in vivo uptake per cell was about three times higher in KC and LEC than in PC. Injection of 125I-TC-t-PA together with mannose inhibited uptake in LEC and increased uptake in PC. Conversely, co-injection with galactose inhibited the uptake of 125I-TC-t-PA in PC and increased the uptake in LEC. Co-injection with excess amounts of unlabelled t-PA shifted the site of uptake from LEC to PC and changed the clearance kinetics to a monophasic β-elimination. The inhibitors used had only marginal effects on the uptake of 125I-TC-t-PA in KC. Although significant amounts of label were recovered in KC, the total size of the population of these cells is relatively small, so that the main hepatic uptake of 125I-TC-t-PA was in LEC and PC.In conclusion, the elimination of t-PA from the blood by the liver is strongly dependent on the structure of its carbohydrate side chains. The main cellular sites of clearance are LEC (via mannose receptors), and PC (via galactose receptors and an unsaturable noncarbohydrate uptake mechanism).

scholarly journals Direct demonstration of actin filament annealing in vitro.

1988 ◽  
Vol 106 (6) ◽  
pp. 1947-1954 ◽  
Author(s):  
D B Murphy ◽  
R O Gray ◽  
W A Grasser ◽  
T D Pollard
Keyword(s):  
Self Assembly ◽  
Actin Filaments ◽  
Atp Hydrolysis ◽  
Electron Microscopic Examination ◽  
Slow Phase ◽  
Electron Microscopic ◽  
Rapid Phase ◽  
Direct Demonstration

Direct electron microscopic examination confirms that short actin filaments rapidly anneal end-to-end in vitro, leading over time to an increase in filament length at steady state. During annealing of mixtures of native unlabeled filaments and glutaraldehyde-fixed filaments labeled with myosin subfragment-1, the structural polarity within heteropolymers is conserved absolutely. Annealing does not appear to require either ATP hydrolysis or the presence of exogenous actin monomers, suggesting that joining occurs through the direct association of filament ends. During recovery from sonication the initial rate of annealing is consistent with a second-order reaction involving the collision of two filament ends with an apparent annealing rate constant of 10(7) M-1s-1. This rapid phase lasts less than 10 s and is followed by a slow phase lasting minutes to hours. Annealing is calculated to contribute minimally to filament elongation during the initial stages of self-assembly. However, the rapid rate of annealing of sonicated fixed filaments observed in vitro suggests that it may be an efficient mechanism for repairing breaks in filaments and that annealing together with polymer-severing mechanisms may contribute significantly to the dynamics and function of actin filaments in vivo.

scholarly journals Turnover and uptake by organs of radioactive serum high-density lipoprotein cholesteryl esters and phospholipids in the rat in vivo

1981 ◽  
Vol 196 (3) ◽  
pp. 877-885 ◽  
Author(s):  
Ferdinand M. Van't Hooft ◽  
Teus Van Gent ◽  
Arie Van Tol
Keyword(s):  
High Density Lipoprotein ◽  
Partial Hepatectomy ◽  
Density Lipoprotein ◽  
Slow Phase ◽  
Sham Operation ◽  
Cholesteryl Esters ◽  
Rapid Phase ◽  
Serum High Density Lipoprotein ◽  
T Values

The serum decay of rat serum high-density lipoprotein (HD lipoprotein), labelled biosynthetically with 32P in the phospholipid or with 3H in the cholesteryl ester moiety, was measured in rats after partial hepatectomy or sham operation. The serum decay of 3H-labelled HD lipoprotein cholesteryl esters was biexponential. In sham-operated rats the t½ values for the rapid phase and the slow phase were 0.2±0.1h and 4.2±0.4h (means±s.e.m.) respectively. After removal of two-thirds of the liver the t½ value of the rapid phase did not change (0.1±0.1h), whereas the t½ value of the slow phase increased to 5.7±0.8h. Partial hepatectomy hardly changed extrahepatic tissue radioactivities, whereas the percentage of the injected dose recovered in the liver 6h after injection decreased from 34.0±1.9% before to 13.5±1.6% after partial hepatectomy. The 32P-labelled HD lipoprotein phospholipids showed a rapid monoexponential decay from serum with t½ values of 0.71±0.3h and 1.48±0.11h after sham operation or partial hepatectomy respectively. The tissue 32P radioactivities in the shamoperated rats, measured 1h after injection, were 46.0±1.7% (liver), 1.7±0.3% (adipose tissue), 3.7±1.2% (skeletal muscle) and 3.0±0.0% (erythrocytes) of the injected dose. Only the value for liver was affected by partial hepatectomy and decreased to 16.7±3.8%. In a previous publication [Van Tol, Van Gent, Van' Hooft & Vlaspolder (1978) Atherosclerosis29, 439–448] we showed in a highly comparable experimental setting that the turnover rates of HD apolipoproteins A and C in vivo are not influenced by removal of two-thirds of the liver. From the present study it is clear that the removal rates of radioactive HD lipoprotein cholesteryl esters and HD lipoprotein phospholipids from serum in vivo are decreased by partial hepatectomy. The results indicate the possibility of partly separate metabolic pathways of HD apolipoproteins A and C, HD lipoprotein cholesteryl esters and HD lipoprotein phospholipids. The phospholipids and cholesteryl esters of HD lipoprotein are metabolized predominantly by the liver. Possible mechanisms for the hepatic uptake and metabolism of HD lipoprotein cholesteryl (esters) and phospholipids are discussed.

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