Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “intercellular communication”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,081 records · Page 60Linked to original sources
PubMed1990

Analysis of gain-of-function mutations of the lin-12 gene of Caenorhabditis elegans.

Certain cell fate decisions are specified by cell-cell interactions during the development of the nematode Caenorhabditis elegans. For example, in a wild-type hermaphrodite gonad, two cells, Z1.ppp and Z4.aaa, have the potential to become the anchor cell (AC). Intercellular communication establishes their fates and ensures that only one cell becomes the AC, while the other becomes a ventral uterine precursor cell (VU). One component of this intercellular communication seems to be the 'AC-to-VU' signal from the presumptive AC that causes the other cell to become a VU. Genetic and developmental studies indicated that the lin-12 gene specifies the fates of Z1.ppp and Z4.aaa. Molecular studies suggest that lin-12 directly participates in their communications, perhaps acting as the receptor for the 'AC-to-VU' signal. Here, we report the molecular lesions associated with lin-12 gain-of-function mutations, cell isolation experiments, and genetic studies of an unusual lin-12 allele. These data suggest that self-association of the putative lin-12-encoded receptor leads to its activation, and that certain gain-of-function mutations result in ligand-independent activation.

Alleles↗
PubMed1997

Transfection of rhabdomyosarcoma cells with connexin43 induces myogenic differentiation.

Normal cell physiological processes rely heavily on cues from the extracellular environment to coordinate the proper functioning of cellular activities. The intercellular communication that takes place through gap junctions in neighboring cells has been implicated in growth control and embryonic differentiation. Indeed, many tumorigenic cells induced to overexpress gap junction proteins exhibit increased differentiation and decreased cell proliferation. Although absent in mature skeletal muscle, studies have demonstrated that gap junctions are present during the early stages of myogenesis, indicating their possible role in muscle development. In our present study, we have attempted to induce a more differentiated phenotype in communication-deficient rhabdomyosarcoma cells. These tumorigenic human cells were transfected with cDNA encoding the gap junction protein connexin43 (Cx43) such that clones of varying expression were isolated. Intercellular communication as measured with dye passage assays was directly proportional to the level of Cx43 expressed, and in those cells expressing Cx43 at high levels, a marked increase in cell membrane fusion and myosin expression was observed. Furthermore, clones expressing Cx43 at high levels exhibited a significant reduction in growth rate when grown under nonadhesive conditions, an indication that their tumorigenicity had been reduced. This apparent increase in myogenic differentiation lends further evidence to the possible role of gap junctional coupling during developmental processes.

Cell Differentiation↗
PubMed1994

Dissociation of PDGF receptor tyrosine kinase activity from PDGF-mediated inhibition of gap junctional communication.

Gap junction-mediated intercellular communication (GJC) may play an important role in cell proliferation and transformation since GJC is inhibited by growth factors, oncogenes, tumor promoters, and carcinogens. We have studied inhibition of GJC by platelet-derived growth factor-BB (PDGF) in the mouse fibroblast cell line C3H/10T1/2 and have sought to determine whether PDGF-induced inhibition of GJC is mediated by the PDGF receptor tyrosine kinase (RTK). PDGF-mediated inhibition of GJC was rapid and transient, with maximal inhibition occurring 40 min after PDGF addition and GJC returning to control levels after 70 min. The effect of PDGF on GJC was concentration-dependent, with maximal inhibition of 90% or greater occurring at 10 ng/ml PDGF. Stimulation of RTK activity, as determined by antiphosphotyrosine immunoblot analysis of PDGF receptor and the receptor substrates phospholipase C-gamma I (PLC-gamma I) and guanosine triphosphatase activating protein (GAP), was also concentration-dependent. Inhibition of GJC required a greater concentration of PDGF than did stimulation of RTK activity. The tyrosine kinase inhibitor genistein blocked PDGF-induced RTK activity, as measured by PDGF receptor, PLC-gamma I, and GAP tyrosine phosphorylation, in a concentration-dependent manner but did not affect PDGF-mediated inhibition of GJC. Genistein alone had no effect on GJC or PDGF receptor expression. PDGF treatment in the presence or absence of genistein resulted in phosphorylation of the connexin 43 protein on nontyrosine residues. These results suggest that inhibition of GJC by ligand-activated PDGF receptor is dissociable from the RTK activity responsible for PDGF, PLC-gamma I, and GAP phosphorylation.

Animals↗
PubMed1980

Cell communication in breast cancer.

Direct intercellular communication is the transfer of ions and small molecules between cells in contact. Cells derived from human breast tissue have been examined to determine their pattern of direct communication, which was measured by the 3H-uridine nucleotide transfer method. The behaviour of mammary epithelium from normal and pathological sources has been compared with that of malignant mammary epithelium. Normal human mammary fibroblasts and epithelium demonstrate selectivity in direct communication. Thus although both transfer nucleotide to and from their own cell type, they do not transfer nucleotide between one another in heterologous co-culture. Further study of a variety of non-human fibroblasts and epithelium showed that cells may be functionally subdivided into selective communicators, non-selective communicators, and non-communicators. None of the malignant human breast cells examined showed selectivity in communication. Thus both primary cultures and established lines were either non-communicators or non-selective communicators. This loss of selectivity could favour the metastasis of malignant cells, enabling them either to ignore inhibitory growth control signals or alternatively to receive stimulatory signals from abnormal sources.

Breast↗
PubMed1984

Inhibition of cell communication between Balb/c 3T3 cells by tumor promoters and protection by cAMP.

The effect of phorbol ester tumor promoters on the communication between individual cells in confluent culture was studied using a fluorescent dye transfer method. Cell-cell communication between mouse Balb/c 3T3 cells and between Chinese hamster V79 cells was inhibited almost completely by tumor-promoting phorbol esters, but not by nonpromoting derivatives; the effect was reversed upon removal of the promoter. Intercellular communication between Balb/c 3T3 cells, but not Chinese hamster V79 cells, was increased significantly in the presence of dbcAMP and caffeine, and these compounds counteracted the effects of tumor promoters. Inhibition of cell communication by phorbol esters appears to be receptor-mediated, since specific binding of 3H-phorbol-12,13-dibutyrate to Balb/c 3T3 cells was inhibited only by compounds that also inhibit intercellular dye transfer. A study with cycloheximide suggests that the reversible inhibition of intercellular communication by phorbol esters may not need de novo protein synthesis, while upregulation of communication by cAMP requires protein synthesis.

Animals↗
PubMed2003

Accelerated hippocampal spreading depression and enhanced locomotory activity in mice with astrocyte-directed inactivation of connexin43.

Using a human glial fibrillary acidic protein (hGFAP) promoter-driven cre transgene, we have achieved efficient inactivation of a floxed connexin43 (Cx43) gene in astrocytes of adult mice. The loss of Cx43 expression was monitored in a cell-autonomous manner via conditional replacement of the Cx43-coding region by a lacZ reporter gene. In this way, we bypassed the early postnatal lethality previously reported for Cx43 null mice and characterized the phenotypic consequences of Cx43 deficiency in the CNS. Mice lacking Cx43 in astrocytes were viable and showed no evidence of either neurodegeneration or astrogliosis. Spreading depression (SD) is a pathophysiological phenomenon observed in the CNS that is characterized by a propagating wave of depolarization followed by neuronal inactivation. Inhibitors of gap junctional communication have previously been shown to block initiation and propagation of SD. In contrast, we observed an increase in the velocity of hippocampal SD in the stratum radiatum of mice lacking Cx43 in astrocytes. In the same brain subregion, dye-coupling experiments revealed a reduction in overall astrocytic intercellular communication by approximately 50%. This strongly suggests separate and different neuronal and glial contributions of gap junctional intercellular communication to SD. Concomitant with increased velocity of spreading depression, we observed enhanced locomotory activity in mice lacking Cx43 in astrocytes.

Animals↗
PubMed2001

Physiological roles for K+ channels and gap junctions in urogenital smooth muscle: implications for improved understanding of urogenital function, disease and therapy.

Smooth muscle cells constitute a heterogeneous collection of effector cells that, by virtue of both their constituency in blood vessels and presence as primary parenchymal cells in diverse tissues, affect the function of all organs. Thus, perhaps it is not surprising that alterations in, and/or dysfunction of, smooth muscle cells are quite common, and responsible, at least in part, for the morbidity and mortality associated with a very wide range of human diseases. These facts point to the necessity for improved understanding of the mechanism(s) governing the control of myocyte contractility (i.e., tone). Such understanding has been rapidly forthcoming in recent years, and has indicated that in many smooth muscle cell types intercellular communication through gap junctions acts in concert with nonjunctional (K+) ion channels to make important contributions to the control of myocyte tone and tissue homeostasis in physiologically diverse organs. Intercellular communication through connexin43-derived gap junction channels and K+ flux through the KCa and KATP channel subtypes, in particular, appear to play prominent roles in this process. The goal of this report, therefore, is to review the data concerning junctional and nonjunctional ion channels on the detrusor myocytes of the urinary bladder, as well as on the specialized vascular myocytes of the corpus cavernosum. The choice of an excitable (i.e., bladder detrusor myocytes) and nonexcitable (i.e., corporal smooth muscle) smooth muscle cell type ensures that the discussion will at least encompass consideration of a large portion of the spectrum of physiological possibilities for the participation of junctional and nonjunctional ion channels in the initiation, maintenance and modulation of smooth muscle tone. A central thesis of this communication is that detailed knowledge of the myocyte- and tissue-specific properties of K+ channels and gap junctions will likely lead to the improved understanding and treatment of human smooth muscle diseases/disorders.

Animals↗
PubMed1993

Gap junctions in the brain: where, what type, how many and why?

Gap junctions represent well-documented means of intercellular communication in various tissues, including the brain, where they function as portals allowing the exchange of electrolytes, second messengers and metabolites between cells. In view of the enormous recent surge of information dealing with the cellular and molecular biology of gap junctions in non-nervous tissue, as well as current interest in the cell biology of glia, this review is intended to provide an overview of the molecular and functional implications of gap-junction-mediated intercellular communication in the nervous system.

Animals↗
PubMed2002

Intercellular calcium signaling in astrocytes via ATP release through connexin hemichannels.

Astrocytes are capable of widespread intercellular communication via propagated increases in intracellular Ca(2+) concentration. We have used patch clamp, dye flux, ATP assay, and Ca(2+) imaging techniques to show that one mechanism for this intercellular Ca(2+) signaling in astrocytes is the release of ATP through connexin channels ("hemichannels") in individual cells. Astrocytes showed low Ca(2+)-activated whole-cell currents consistent with connexin hemichannel currents that were inhibited by the connexin channel inhibitor flufenamic acid (FFA). Astrocytes also showed molecular weight-specific influx and release of dyes, consistent with flux through connexin hemichannels. Transmembrane dye flux evoked by mechanical stimulation was potentiated by low Ca(2+) and was inhibited by FFA and Gd(3+). Mechanical stimulation also evoked release of ATP that was potentiated by low Ca(2+) and inhibited by FFA and Gd(3+). Similar whole-cell currents, transmembrane dye flux, and ATP release were observed in C6 glioma cells expressing connexin43 but were not observed in parent C6 cells. The connexin hemichannel activator quinine evoked ATP release and Ca(2+) signaling in astrocytes and in C6 cells expressing connexin43. The propagation of intercellular Ca(2+) waves in astrocytes was also potentiated by quinine and inhibited by FFA and Gd(3+). Release of ATP through connexin hemichannels represents a novel signaling pathway for intercellular communication in astrocytes and other non-excitable cells.

Adenosine Triphosphate↗
PubMed2000

Cellular communication in clone 9 cells exposed to magnetic fields.

Magnetic-field exposure (45 Hz B(a.c.) over a flux density range of 7.7 to 49.9 microT r.m.s. with parallel B(d.c.) of 36.6 microT) has been reported by Blackman and coworkers to inhibit gap junction intercellular communication in Clone 9 cells treated with chloral hydrate for 24 h prior to field exposure in accord with predictions of the ion parametric resonance model. The study reported here is an attempt to reproduce this effect. Baseline experiments showed that growth in culture and state of confluence at time of addition of chloral hydrate were comparable in both laboratories. PMA inhibited cell-cell communication in a dose-dependent manner, similar to the results of Blackman and coworkers, whereas cells in the present study were somewhat more sensitive to chloral hydrate than reported by Blackman and coworkers. A total of 38 exposure experiments were undertaken using a 45 Hz magnetic field with a flux density of 23.8 microT r.m.s., in parallel with a 36.6-microT static magnetic field for 40 to 45 min, after pretreatment with 2.5 mM chloral hydrate for 24 h. In 14 unblinded experiments, a small but statistically significant effect of magnetic-field exposure was observed, but due to the subjective nature of the assay, it was deemed essential to carry out blinded experiments. The remaining 24 experiments were blinded. In 15 blinded experiments, cells purchased from the American Type Culture Collection and grown only in this laboratory were used, while in 9 experiments, the cells had originally been grown in Blackman's laboratory and were subsequently sent to this laboratory. There was no statistically significant effect of magnetic-field exposure on gap junction intercellular communication in these blinded experiments using either cell line.

Animals↗
PubMed2000

Regulation of connexin degradation as a mechanism to increase gap junction assembly and function.

Connexins, the integral membrane protein constituents of gap junctions, are degraded at a rate (t(12) = 1.5-5 h) much faster than most other cell surface proteins. Although the turnover of connexins has been shown to be sensitive to inhibitors of either the lysosome or of the proteasome, how connexins are targeted for degradation and whether this process can be regulated to affect intercellular communication is unknown. We show here that reducing connexin degradation with inhibitors of the proteasome (but not with lysosomal blockers) is associated with a striking increase in gap junction assembly and intercellular dye transfer in cells inefficient in both processes under basal conditions. The effect of proteasome inhibitors on wild-type connexin stability, assembly, and function was mimicked by treatment of assembly-inefficient cells with inhibitors of protein synthesis such as cycloheximide. Sensitivity of connexin degradation to cycloheximide, but not to proteasome inhibitors, was abolished when connexins were rendered structurally abnormal by perturbation of essential disulfide bonds or by mutation. Our findings provide the first evidence that intercellular communication can be up-regulated at the level of connexin turnover and that a short-lived protein may be required for conformationally mature connexins to become substrates of proteasomal degradation.

Animals↗
PubMed2001

Connexin expression by alveolar epithelial cells is regulated by extracellular matrix.

Extracellular matrix (ECM) proteins promote attachment, spreading, and differentiation of cultured alveolar type II epithelial cells. The present studies address the hypothesis that the ECM also regulates expression and function of gap junction proteins, connexins, in this cell population. Expression of cellular fibronectin and connexin (Cx) 43 increase in parallel during early type II cell culture as Cx26 expression declines. Gap junction intercellular communication is established over the same interval. Cells plated on a preformed, type II cell-derived, fibronectin-rich ECM demonstrate accelerated formation of gap junction plaques and elevated gap junction intercellular communication. These effects are blocked by antibodies against fibronectin, which cause redistribution of Cx43 protein from the plasma membrane to the cytoplasm. Conversely, cells cultured on a laminin-rich ECM, Matrigel, express low levels of Cx43 but high levels of Cx26, reflecting both transcriptional and translational regulation. Cx26 and Cx43 thus demonstrate reciprocal regulation by ECM constituents.

Animals↗
PubMed2003

A genomewide survey of developmentally relevant genes in Ciona intestinalis. X. Genes for cell junctions and extracellular matrix.

Cell junctions and the extracellular matrix (ECM) are crucial components in intercellular communication. These systems are thought to have become highly diversified during the course of vertebrate evolution. In the present study, we have examined whether the ancestral chordate already had such vertebrate systems for intercellular communication, for which we have searched the genome of the ascidian Ciona intestinalis. From this molecular perspective, the Ciona genome contains genes that encode protein components of tight junctions, hemidesmosomes and connexin-based gap junctions, as well as of adherens junctions and focal adhesions, but it does not have those for desmosomes. The latter omission is curious, and the ascidian type-I cadherins may represent an ancestral form of the vertebrate type-I cadherins and desmosomal cadherins, while Ci-Plakin may represent an ancestral protein of the vertebrate desmoplakins and plectins. If this is the case, then ascidians may have retained ancestral desmosome-like structures, as suggested by previous electron-microscopic observations. In addition, ECM genes that have been regarded as vertebrate-specific were also found in the Ciona genome. These results suggest that the last common ancestor shared by ascidians and vertebrates, the ancestor of the entire chordate clade, had essentially the same systems of cell junctions as those in extant vertebrates. However, the number of such genes for each family in the Ciona genome is far smaller than that in vertebrate genomes. In vertebrates these ancestral cell junctions appear to have evolved into more diverse, and possibly more complex, forms, compared with those in their urochordate siblings.

Animals↗
PubMedDate not supplied

Connexin43 gene expression in the rabbit arterial wall: effects of hypercholesterolemia, balloon injury and their combination.

The specialized functions of endothelium require intercellular communication between endothelial cells within the monolayer, and between endothelium and other cells present in the vessel wall. This is accomplished by a combination of paracrine soluble mediators and direct gap-junctional intercellular communication (GJIC) mediated by a family of connexin proteins. A prominent connexin expressed by vascular cells in vivo and in vitro is connexin 43 (Cx43). We have investigated the in vivo gene regulation of Cx43 in the context of vascular pathology, as a result of mechanical injury, hypercholesterolemia or both. The aortoiliac bifurcation in the rabbit was examined following three types of insult: (1) diet-induced hypercholesterolemia resulting in macrophage-rich fatty streak lesions, (2) mechanical, stretch-denudation injury resulting in intimal smooth muscle cell (SMC) proliferation and (3) mechanical injury superimposed on hypercholesterolemia resulting in a complex vascular lesion having characteristics of both interventions. The normal rabbit iliac artery expressed approximately equal levels of Cx43 mRNA in the medial SMC layers and in the endothelium. In hypercholesterolemia-induced atherosclerosis, Cx43 expression was most prominent in macrophage foam cells even though normocholesterolemic precursor monocytes did not express Cx43 mRNA. Antibodies directed specifically to Cx43 protein confirmed the expression of macrophage gap junction protein in these cells. Medial SMC in hypercholesterolemia exhibited less Cx43 than their normal counterparts in control animals. Mechanical injury in the absence of hypercholesterolemia resulted in intimal thickening in which Cx43 expression in the intimal SMC was equivalent to that in the subjacent medial SMC, both being approximately equivalent to normal uninjured rabbit medial SMC expression. Cell-specific expression of Cx43 in combined mechanical injury/hypercholesterolemia was similar to that observed in hypercholesterolemia alone: Cx43 upregulation in macrophages, while medial SMC were downregulated. Normo- and hypercholesterolemic alveolar macrophages of the lung and Kupffer cells of the liver did not exhibit induction of Cx43 mRNA, nor did macrophages isolated from peritoneal or bronchial lavage fluid of the same animals. This work extends our previous finding of Cx43 upregulation in human atherectomy tissue and demonstrates that atherosclerotic lesions in situ, in a controlled animal model of atherosclerosis, exhibit cell-specific changes in Cx43 gene expression. Changes in medial SMC migration, proliferation and phenotype, as well as enhanced interactions between adherent/infiltrating monocytes and endothelium may be related to modified GJIC pathways in the vessel wall.

Animals↗
PubMed2005

In vivo and in vitro expression of connexins in the human corneal epithelium.

PURPOSE: This study is designed to provide a comprehensive expression profile of connexins in the human corneal epithelium (in vivo) and in cultured primary corneal epithelial cells (PCECs) (in vitro). It also evaluates the pathologic effects of a pathogenic missense mutation in Cx26, which causes keratitis-ichthyosis-deafness syndrome (KIDS), a rare genetic disorder with corneal involvement. METHODS: RT-PCR analysis, immunohistochemistry, and fluorescent dye transfer assays were used to determine the expression pattern and gap junction intercellular communication in PCECs and human cornea. Differentiation-dependent differences in connexin expression of PCECs after a calcium switch were verified by real-time RT-PCR. The common KIDS mutation Cx26(D50N) was studied by determining transient expression in PCECs. RESULTS: In vivo immunostaining revealed widespread and overlapping expression of Cx43 and -30 in the basal and suprabasal layers. Cx26 staining was limited to the lower suprabasal cells, whereas Cx31.1 localized to the apical surface of basal cells in the central cornea and to the lower and middle suprabasal cells in the limbal region. Immunostaining for nine other connexins, including Cx50, was negative. In PCEC, nine connexin genes were detectable by RT-PCR, however, only Cx26, -30, and -43 formed visible gap junction plaques. High-Ca(2+) culture conditions were accompanied by a 1.6- to 2.2-fold upregulation of expression of Cx26, -30, and -43 and a significant increase in gap-junction-mediated dye transfer. Transient expression of mutant Cx26(D50N) in PCECs resulted in cytoplasmic accumulation and lack of gap junction plaque formation and was not altered by coexpression of wild-type (wt)Cx26 or -30. CONCLUSIONS: Gap junction communication in the human corneal epithelium is mediated by Cx26, -30, -31.1, and -43. Poorly differentiated PCECs are uncoupled, and Ca(2+) induced differentiation is associated with an upregulation of connexin expression and intercellular communication. The transfection experiments suggest that KIDS Cx26(D50N) impairs intracellular formation and transport of connexons formed by Cx26 and -30, consistent with a dominant negative effect.

Adult↗
PubMed2005

Dye coupling in Purkinje cells of organotypic slice cultures.

Cerebellar slice cultures of newborn rats showed poorly developed dendritic arborization of Purkinje cells, whereas cultures of 10-day-old rats revealed prominent dendritic branching. Gap junctional intercellular communication between Purkinje cells, investigated as dye transfer of microinjected neurobiotin, occurred through dendro-dendritic contacts, with decreased dye spreading in old cell cultures. These results indicate a possible correlation of gap junctional intercellular communication and the development of Purkinje cells.

Animals↗
PubMed1998

Functional gap junctions in corneal fibroblasts and myofibroblasts.

PURPOSE: Within the corneal stroma, keratocytes communicate through gap junctions. These plasma membrane channels, which connect the cytoplasm of adjacent cells, are composed of connexins. In a cell culture model, an investigation was conducted to determine whether connexin-based gap junction intercellular communication is present in fibroblasts and myofibroblasts, both of which replace keratocytes after wounding. METHODS: Fibroblasts and myofibroblasts were grown according to preestablished methods. Phenotype was determined by immunocytochemistry. A gap junction-permeant dye, Lucifer yellow or Cascade blue, and nonpermeant 10-kDa Texas red-dextran were used. Tracer fluorescent dyes were introduced by scrape-loading or by microinjection, and their diffusion into adjacent cells was recorded photographically. Inhibition of gap junction dye transfer was elicited by treatment with 18-alpha-glycyrrhetinic acid (AGA). RESULTS: In confluent fibroblast or myofibroblast cultures, the scrape-loaded dextran probe remained within wounded cells, whereas the Lucifer yellow or Cascade blue dye diffused into adjacent intact cells. Similarly, in nonconfluent fibroblast and myofibroblast cultures, microinjected Lucifer yellow rapidly diffused from the microinjected cell to adjacent cells. Treatment with 2 microM AGA, an uncoupling agent, blocked the spread of Lucifer yellow in fibroblast and myofibroblast cultures. CONCLUSIONS: Cultured fibroblasts and myofibroblasts have functional gap junctions as has previously been demonstrated for keratocytes in vivo. Thus, fibroblasts and myofibroblasts have the ability to establish and maintain intercellular communication with themselves and with nonactivated keratocytes. This property may be critical in the wound-healing process, especially in the avascular corneal environment.

Actins↗
PubMed1997

Dye spread through gap junctions in the corneal epithelium of the rabbit.

PURPOSE: Microelectrode dye injection of 5,6-carboxyfluorescein was used to investigate gap junctional communication in the corneal epithelium. METHODS: Dye injection started in the superficial layer and proceeded stepwise into the underlying epithelial layers until spread was observed. Intracellular [Ca2+] was manipulated by exposing the cornea to the calcium ionophore A23187 (global increase) or by increasing the [Ca2+] in the injection electrode (source cell increase). Intracellular pH was manipulated by exposing the cornea to nigericin in a low-pH KCI Ringer's (global decrease) or by lowering the pH in the injection electrode (source cell decrease). Heptanol was tested for its ability to uncouple gap junctions. Gap junctional communication was based on the layer at which spread was first observed and on the apparent dye travel distance from the point of injection. RESULTS: Control dye spread occurred, on average, in the third layer from the surface. Increased [Ca2+] in the source cell resulted in an initial spread occurring in the second layer. Globally increasing [Ca2+] with A23187 resulted in no change in the average initial spread layer. Lowering intracellular pH of the source cell did not affect the initial dye spread layer. Globally lowering intracellular pH resulted in significant gap junctional inhibition in a time-dependent manner. Dye spread distance was not significantly affected by [Ca2+] or pH manipulations. Heptanol (2.5 mM) completely inhibited dye coupling. CONCLUSION: All cell layers of the corneal epithelium contain functional gap junctions, although it appears that intercellular communication in the superficial layers does not occur under our control conditions. Intercellular communication through these junctions can be altered by various manipulations of [Ca2+] and pH.

Alcohols↗