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Title: Hormonal regulation of hepatocyte tight junctional permeability

Abstract

The authors have investigated the effects of hormones on the permeability of the hepatocyte tight junction to two probes, ({sup 14}C)sucrose and horseradish peroxidase, using one-pass perfused rat livers. Using a single injection of horseradish peroxidase the authors have demonstrated that this probe can enter bile by two pathways that are kinetically distinct, a fast pathway, which corresponds to the passage of the probe through the hepatocyte tight junctions, and a slow pathway, which corresponds to the transcytotic entry into bile. The passage of horseradish peroxidase through the hepatocyte tight junctions was confirmed by electron microscopic histochemistry. Vasopressin, epinephrine, and angiotensin II, hormones that act in the hepatocyte through the intracellular mediators calcium, the inositol polyphosphates, and diacylglycerol, increased the bile-to-perfusion fluid ratio of ({sup 14}C)sucrose and the rapid entry of horseradish peroxidase into bile, indicating that the permeability of the tight junctions to these probes was increased. The effect of these hormones was dose dependent and in the cases of angiotensin II and epinephrine was inhibited by the specific inhibitors (Sar{sup 1},Thr{sup 8})angiotensin II and prazosin, respectively. Dibutyryl adenosine 3{prime},5{prime}-cyclic monophosphate did not affect the ({sup 14}C)sucrose bile-to-perfusion fluid ratio or the fast entry of horseradish peroxidase into bile.more » These results suggest that the hepatocyte tight junction can no longer be considered a static system of pores separating blood from bile. It is rather a dynamic barrier potentially capable of influencing the composition of the bile.« less

Authors:
; ; ;  [1]
  1. (Veterans Administration Medical Center, San Diego, CA (USA) Univ. of California, San Diego (USA))
Publication Date:
OSTI Identifier:
6228279
Resource Type:
Journal Article
Resource Relation:
Journal Name: American Journal of Physiology; (USA); Journal Volume: 255:4
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; LIVER; TRANSMISSION ELECTRON MICROSCOPY; LIVER CELLS; PERMEABILITY; PEPTIDE HORMONES; BIOCHEMISTRY; ANGIOTENSIN; CARBON 14 COMPOUNDS; PERFUSED TISSUES; RATS; SACCHAROSE; ANIMAL CELLS; ANIMAL TISSUES; ANIMALS; BODY; CARBOHYDRATES; CARDIOVASCULAR AGENTS; CHEMISTRY; DIGESTIVE SYSTEM; DISACCHARIDES; DRUGS; ELECTRON MICROSCOPY; GLANDS; GLOBULINS; HORMONES; LABELLED COMPOUNDS; MAMMALS; MICROSCOPY; OLIGOSACCHARIDES; ORGANIC COMPOUNDS; ORGANS; PROTEINS; RODENTS; SACCHARIDES; SOMATIC CELLS; TISSUES; VASOCONSTRICTORS; VERTEBRATES; 551001* - Physiological Systems- Tracer Techniques

Citation Formats

Lowe, P.J., Miyai, K., Steinbach, J.H., and Hardison, W.G.M.. Hormonal regulation of hepatocyte tight junctional permeability. United States: N. p., 1988. Web.
Lowe, P.J., Miyai, K., Steinbach, J.H., & Hardison, W.G.M.. Hormonal regulation of hepatocyte tight junctional permeability. United States.
Lowe, P.J., Miyai, K., Steinbach, J.H., and Hardison, W.G.M.. Sat . "Hormonal regulation of hepatocyte tight junctional permeability". United States. doi:.
@article{osti_6228279,
title = {Hormonal regulation of hepatocyte tight junctional permeability},
author = {Lowe, P.J. and Miyai, K. and Steinbach, J.H. and Hardison, W.G.M.},
abstractNote = {The authors have investigated the effects of hormones on the permeability of the hepatocyte tight junction to two probes, ({sup 14}C)sucrose and horseradish peroxidase, using one-pass perfused rat livers. Using a single injection of horseradish peroxidase the authors have demonstrated that this probe can enter bile by two pathways that are kinetically distinct, a fast pathway, which corresponds to the passage of the probe through the hepatocyte tight junctions, and a slow pathway, which corresponds to the transcytotic entry into bile. The passage of horseradish peroxidase through the hepatocyte tight junctions was confirmed by electron microscopic histochemistry. Vasopressin, epinephrine, and angiotensin II, hormones that act in the hepatocyte through the intracellular mediators calcium, the inositol polyphosphates, and diacylglycerol, increased the bile-to-perfusion fluid ratio of ({sup 14}C)sucrose and the rapid entry of horseradish peroxidase into bile, indicating that the permeability of the tight junctions to these probes was increased. The effect of these hormones was dose dependent and in the cases of angiotensin II and epinephrine was inhibited by the specific inhibitors (Sar{sup 1},Thr{sup 8})angiotensin II and prazosin, respectively. Dibutyryl adenosine 3{prime},5{prime}-cyclic monophosphate did not affect the ({sup 14}C)sucrose bile-to-perfusion fluid ratio or the fast entry of horseradish peroxidase into bile. These results suggest that the hepatocyte tight junction can no longer be considered a static system of pores separating blood from bile. It is rather a dynamic barrier potentially capable of influencing the composition of the bile.},
doi = {},
journal = {American Journal of Physiology; (USA)},
number = ,
volume = 255:4,
place = {United States},
year = {Sat Oct 01 00:00:00 EDT 1988},
month = {Sat Oct 01 00:00:00 EDT 1988}
}
  • Multidrug resistance-associated protein 2 (MRP2) (ABCC2) is an ATP-binding cassette membrane protein located primarily on apical surface of hepatocytes that mediates transport of conjugated xenobiotics and endogenous compounds into bile. MRP2 is highly expressed in hepatocytes, and at lower levels in small intestines, stomach and kidney. Previous reports have characterized mammalian MRP2 promoters, but none have established the molecular mechanism(s) involved in liver enriched expression. This study aims to investigate the mechanism of hepatic MRP2 regulation. A 2130 bp of MRP2 promoter was cloned from PAC-1 clone P108G1-7, to identify putative liver specific/hormone responsive functional DNA binding sites. Using deletionmore » analysis, site specific mutagenesis and co-transfection studies, liver specific expression was determined. MRP2 promoter-LUC constructs were highly expressed in liver cell lines compared to non-liver cells. The region extending from - 3 to+ 458 bp of MRP2 promoter starting from AUG contained the potential binding sites for CAAATT box enhancer binding protein (C/EBP), hepatocytes nuclear factor 1, 3 and 4 (HNF1, HNF3, and HNF4. Only HNF1 and HNF4 co-transfection with MRP2 luciferase increased expression. Site specific mutational analysis of HNF1 binding site indicated an important role for HNF1{alpha}. HNF4{alpha} induction of MRP2 was independent of HNF1 binding site. C/EBP, HNF3, and HNF6 inhibited HNF1{alpha} while HNF4{alpha} induced MRP2 luciferase expression and glucocorticoids stimulated MRP2 expression. This study emphasizes the complex regulation of MRP2 with HNF1{alpha} and HNF4{alpha} playing a central role. The coordinated regulation of xenobiotic transporters and oxidative conjugation may determine the adaptive responses to cellular detoxification processes.« less
  • Tight junctions (TJs) restrict paracellular flux of water and solutes in epithelia and endothelia. In epidermis, the physiological role of TJs is not fully understood. In this study, sodium caprate (C10), which dilates intestinal TJs, was applied to cultured human epidermal keratinocytes and reconstructed human epidermis to investigate the effects of C10 on epidermal TJs. C10 treatment decreased transepithelial electrical resistance and increased paracellular permeability, although Western blots showed that the expression of TJ-related transmembrane proteins was not decreased. The effects of C10 were reversible. Immunofluorescence microscopy and immuno-replica electron microscopy showed that the localization of TJ strands were disintegrated,more » concomitant with the dispersion and/or disappearance of TJ-related molecules from the cell surface. These findings suggest that C10 impairs barrier function by physically disrupting TJ conformation in the epidermis. Furthermore, these results also show that proper localization of the molecules on the cellular membrane is important for TJ barrier function.« less
  • The effect of deuterium oxide on junctional membrane permeability to dichlorofluorescein was examined to determine the mode of transfer of the dye from one cell interior to another in the septate giant axon of earthworm. Dichlorofluorescein was shown to diffuse through the nexus passively and in a hydrated form. Additionally, evidence suggested an alteration of the cell-to-cell channel structure by deuterium/hydrogen exchange. Dichlorofluorescein was rendered impermeant at 6 degrees C in D/sub 2/O and 4 degrees C in H/sub 2/O. Action potentials, however, were capable of propagation from cell to cell at 4 degrees C in D/sub 2/O and H/submore » 2/O. The results are consistent with a hydrophilic channel where solute molecules diffuse through the junction (nexus) in a hydrated form. The temperature blocks are presumably brought about by increasing hydration shells around solute and channel proteins with cooling until the solute is rendered too large to diffuse.« less
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  • The mechanism by which individual peptide and steroid hormones and cell-substratum interactions regulate milk protein gene expression has been studied in the COMMA-D mammary epithelial cell line. In the presence of insulin, hydrocortisone, and prolactin, growth of COMMA-D cells on floating collagen gels in comparison with that on a plastic substratum resulted in a 2.5- to 3-fold increase in the relative rate of ..beta..-casein gene transcription but a 37-fold increase in ..beta..-casein mRNA accumulation. In contrast, whey acidic protein gene transcription was constitutive in COMMA-D cells grown on either substratum, but its mRNA was unstable and little intact mature mRNAmore » was detected. Culturing COMMA-D cells on collagen also promoted increased expression of other genes expressed in differentiated mammary epithelial cells, including those encoding ..cap alpha..- and ..gamma..-casein, transferrin, malic enzyme, and phosphoenolpyruvate carboxykinase but decreased the expression of actin and histone genes. Using COMMA-D cells, the authors defined further the role of individual hormones in influencing ..beta..-casein gene transcription. With insulin alone, a basal level of ..beta..-casein gene transcription was detected in COMMA-D cells grown on floating collagen gels. Addition of prolactin but not hydrocortisone resulted in a 2.5- to 3.0-fold increase in ..beta..-casein gene transcription, but both hormones were required to elicit the maximal 73-fold induction in mRNA accumulation. The posttranscriptional effect of hormones on casein mRNA accummulation preceded any detectable changes in the relative rate of transcription. Thus, regulation by both hormones and cell substratum of casein gene expression is exerted primarily at the post transcriptional level.« less