Biomedical subjects

H Nguyen

Publications and source records attributed to H Nguyen.

At least 145 records · Page 8Linked to original sources

PubMed1996

Developmental alterations in 5-hydroxytryptamine concentration and turnover after treatment of neonatal rats with 5,7-dihydroxytryptamine.

Early disruption of the serotonin neurotransmitter system may have important consequences for normal neuro-physiological development. In order to further understand the neurochemical changes which occur after early insults to the system, intracerebroventricular injections of the serotonin-selective toxin, 5,7-dihydroxytryptamine were given to Sprague-Dawley rat pups on day 3 of life. Serotonin and 5-hydroxyindoleacetic acid concentration in cortex, striatum, hippocampus, and brainstem were measured after 4, 8, and 12 weeks. In controls, serotonin concentration in the striatum and cortex increased from 4 to 12 weeks, while it reached adult levels by 4 weeks in the hippocampus. 5-Hydroxyindoleacetic acid increased in cortex and hippocampus and was unchanged after 4 weeks in the striatum. An index of serotonin turnover (5-hydroxyindoleacetic acid/serotonin) decreased in striatum and cortex, but increased in the hippocampus over time. 5,7-Dihydroxytryptamine treatment induced permanent decreases in serotonin and 5-hydroxyindoleacetic acid concentration in all three forebrain regions, but had no region- and time-specific effects on serotonin turnover. In the brainstem of controls, serotonin concentration increased from 4 to 12 weeks, while 5-hydroxyindoleacetic acid concentration was unchanged, resulting in decreasing turnover. After 5,7-dihydroxytryptamine treatment, the brainstem did not show depletions of serotonin concentration in spite of significant serotonin neuronal loss, suggesting that compensatory mechanisms in remaining neurons may permit increased serotonin production. Regional and time-dependent responses to serotonin depletion may have functional implications for the developmental regulation of serotonin transmission after early insults to this neurotransmitter system.

5,7-Dihydroxytryptamine↗

PubMed1996

Increasing nitric oxide production improves survival in experimental hemorrhagic shock.

UNLABELLED: The purpose of this study was to evaluate the importance of nitric oxide (NO) upon outcome following hemorrhagic shock. L-Arginine, an NO precursor, and L-NMMA, an inhibitor of NO synthesis, were added to resuscitation in a prospective, randomized, and double-blinded experimental model, and the effects upon blood pressure and survival were measured. METHODS: 60 Sprague-Dawley rats were anesthetized and subjected to phlebotomy to induce hemmorrhagic shock. After a 45 min shock period, animals were resuscitated with either lactated Ringer's alone (control), L-NMMA in lactated Ringer's or L-arginine in lactated Ringer's. Blood pressure was monitored, and animals were observed for survival. As an additional control experiment, 15 additional animals underwent the same protocol, but underwent sham shock, i.e. were not haemorrhaged. RESULTS: L-NMMA increased blood pressure transiently following sham shock, but increased blood pressure to a greater extent and for a longer duration following hemorrhage. However, L-NMMA had no effect upon survival. L-Arginine had no measurable effect upon blood pressure, but significantly increased survival. CONCLUSION: NO may play an important role following hemorrhage. The effectiveness of L-NMMA as a pressor suggests that NO contributes to hypotension following hemorrhage. However, reversing hypotension with L-NMMA did not improve survival in this model. In contrast, L-arginine did not further lower blood pressure, but had significant survival benefit. This suggests a possible protective effect of NO after hemorrhage, perhaps by improving the distribution of capillary blood flow and/or by decreasing platelet aggregation and leukocyte adhesion within the microcirculation.

Analysis of Variance↗

PubMed1996

Methodologic standards in surgical trials.

BACKGROUND: Concerns have been raised that flaws in the design and analysis of trials will hinder the interpretation of their relevance to clinical practice. The objective of this study was to review the nature and methodologic standards of surgical trails published in 10 prestigious journals between January 1988 and December 1994. METHODS: We evaluated the demography and methodologic standards of 364 trials. Each article was independently scrutinized by two assessors with documentation of the interassessor variation. RESULTS: Less than 50% of the trials made comment about an unbiased assessment of outcome, gave an adequate description of the randomization technique, or provided a prospective estimate of the sample size. Economic factors were declared in 6.5% of the trials. Only 2% of the trials attempted to measure the effect of an intervention on the quality of life patients. CONCLUSIONS: Readers should be cautious when interpreting the results of surgical trials.

Clinical Trials as Topic↗

PubMed1996

Drug-resistant breast cancer cells frequently retain expression of a functional wild-type p53 protein.

Abnormalities in the p53 tumor suppressor gene have been shown to affect cellular processes related to cell cycle control and gene amplification. In this study we compare the status and function of wild-type p53 in MCF-7 breast cancer cells with sublines selected for resistance to chemotherapeutic agents having different mechanisms of action. Sublines that were resistant to melphalan, pyrazafurin, mitoxantrone, etoposide and PALA all retained expression of wild-type p53. Methotrexate-resistant MCF-7 cells were unusual heterozygotes that expressed a wild-type and dominant, in-frame p53 deletion mutant and the doxorubicin-resistant cells expressed only mutant p53. Analysis of the G1 checkpoint after treatment with ionizing radiation revealed that the pyrazafurin-, melphalan- and mitoxantrone-resistant cells arrested strongly in G1. The etoposide- and PALA-resistant cells had an intermediate G1 arrest phenotype and the methotrexate- and doxorubicin-resistant cells had a minimal G1 arrest phenotype. mRNA and protein analyses of downstream effector genes, including P21CIP1/Waf1, mdm2, Gadd 45 and the retinoblastoma protein, did not entirely differentiate sublines having a strong versus intermediate G1 arrest phenotype. Neither the p53 status nor the strength of the G1 arrest could be correlated with cell survival after ionizing radiation. When drug-sensitive MCF-7 cells were treated with the same chemotherapeutic agents, p53 and p21CIP1/Waf1 levels increased between 2- and 14-fold. Together these data suggest that other cellular factors likely play a role in overcoming the inhibitory effects of ionizing radiation on p53 in drug-resistant breast cancer cells.

Amides↗

PubMed1996

Treatment of old mice with IL-2 corrects dysregulated IL-2 and IL-4 production.

Splenic T cells from old BALB/c mice, activated in vitro with antibody to CD3epsilon, secrete more IL-4 but less IL-2 than splenic T cells from young mice. The age-associated increase in IL-4 secretion is associated with a significantly increased concentration of intracellular IL-4 and its mRNA, although there is no increase in the number of activated T cells with intracellular IL-4. In contrast, the age-associated decrease in IL-2 secretion is associated with a significant decrease in the number of activated T cells with intracellular IL-2. In vivo there is a similar age-associated change in the number of activated T cells with detectable cytokine. The number of activated T cells with intracellular IL-4 is comparable in old and young mice, while the number of activated T cells with intracellular IL-2 is significantly decreased in old compared with young mice. Of great interest is the fact that old mice continuously exposed to IL-2 in vivo following the transplantation of J558 cells expressing the transfected IL-2 gene product have an increased number of splenic T cells with intracellular IL-2 that equals the level of such cells observed in young mice. Most important, the effect of continuous IL-2 administration in vivo was stable as spleen cells from old, IL-2-treated mice when stimulated in vitro with anti-CD3epsilon had a young-like pattern of both intracellular IL-2 and IL-4 expression as well as IL-2 and IL-4 secretion following in vitro activation. Thus, it appears that exposure of old mice to exogenous IL-2 can redress the age-associated imbalance in cytokine expression in vivo and cytokine secretion in vitro.

Age Factors↗

PubMed1996

Stimulated gracilis neosphincter: a new procedure for anal incontinence.

BACKGROUND: The gracilis muscle has been used previously to construct an anal neosphincter, but this was not successful since a short-lived muscle contraction was insufficient to restore continence. Recently, a procedure was described in which conversion to a fatigue-resistant muscle was achieved by chronic low frequency electrical stimulation, and the resultant ability to sustain a constant contraction was associated with improved continence. Our initial results with this procedure, using a standardized operation and treatment protocol in 12 consecutive patients, is reported. METHODS: Seven women (mean age 50 years, range 22-71 years) had faecal incontinence, and five patients (F:M, 3:2; aged 53-72 years) underwent reconstruction after abdominoperineal excision of the rectum for cancer. A detailed questionnaire including continence score was completed pre-operatively. Eight patients have been assessed after ileostomy closure at a mean time of 10 months. RESULTS: Slow-twitch muscle conversion was achieved in each case and all patients have a functional neosphincter. Mean continence score was 6.8 (range 4-12), and seven patients were continent. There was significant improvement in continence in the non-cancer group (p = 0.03). Mean pre-operative resting anal pressure, functional neosphincter pressure (NPfunc), and maximal neosphincter pressure (NP(max)) were 36, 102 and 207 cmH2O, respectively. There was a significant improvement in pressure comparing NPfunc (P = 0.03) and NP(max) (P = 0.03) with pre-operative pressure. Complications included deep vein thrombosis, pulmonary embolism, saphenous nerve injury, leg wound haematoma, and late pacemaker infection. CONCLUSION: The stimulated gracilis neosphincter achieves satisfactory continence in a majority of patients.

Adult↗

PubMed1996

Delta F508-CFTR channels: kinetics, activation by forskolin, and potentiation by xanthines.

Trafficking, activation, and kinetics of delta F508-cystic fibrosis transmembrane conductance regulator (CFTR) and CFTR were compared in stably transduced C127I mouse mammary epithelial cells. Western blots detected a small amount of fully glycosylated delta F508-CFTR Efflux of 125I was stimulated by forskolin with the same mean effective concentration (EC50; approximately 0.5 microM) for CFTR and delta F508-CFTR cells, but the maximum response was reduced more than fivefold and its latency increased approximately threefold in delta F508-CFTR cells. In delta F508-CFTR cells, 3-isobutyl-1-methylxanthine (IBMX; EC50 = 1.45 microM) and 8-cyclopentyl-1,3-dipropylxanthine (CPX; EC50 = 58 microM) increased the peak forskolin-stimulated efflux rate approximately 2.5-fold and decreased the time to peak. A sevenfold increase in intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels accompanied potentiation of forskolin-induced 125I efflux by IBMX but not by CPX. Elevation of intracellular cAMP increased linear voltage-independent whole cell currents 30-fold in CFTR and 4-fold in delta F508-CFTR cells; the response rate in delta F508-CFTR cells was much slower. Single-channel currents were detected in 57 of 68 cell-attached patches from forskolin-prestimulated CFTR cells vs. 6 of 35 patches in delta F508-CFTR cells. Mean number of active channels per patch was 4.1 for CFTR [open probability (Po) = 0.34] and 0.2 for delta F508-CFTR (Po = 0.11). The lower Po of delta F508-CFTR resulted from an approximately threefold longer mean interburst interval. We estimate that forskolin-stimulated chloride conductance of delta F508-CFTR C127I cells is < 5% of CFTR cells. CPX is approximately 25-fold more potent than IBMX in potentiating delta F508-CFTR and may operate by a mechanism other than elevation of cAMP.

1-Methyl-3-isobutylxanthine↗

PubMed1996

Characterization of brimonidine metabolism with rat, rabbit, dog, monkey and human liver fractions and rabbit liver aldehyde oxidase.

1. In vitro metabolism of 14C-brimonidine by the rat, rabbit, dog, monkey and human liver fractions was studied to assess any species differences. In vitro metabolism with rabbit liver aldehyde oxidase and human liver slices, and in vivo metabolism in rats were also investigated. The hepatic and urinary metabolites were characterized by liquid chromatography and mass spectrometry. 2. Up to seven, six, 11 and 14 metabolites were detected in rat liver S9 fraction, human liver S9 fraction, human liver slices and rat urine respectively. Rabbit liver aldehyde oxidase catalysed the metabolism of brimonidine to 2-oxobrimonidine and 3-oxobrimonidine, and further oxidation to the 2,3-dioxobrimonidine. Menadione inhibited the liver aldehyde oxidase-mediated oxidation. 3. Hepatic oxidation of brimonidine to 2-oxobrimonidine, 3-oxobrimonidine and 2,3-dioxobrimonidine was a major pathway in all the species studied, except the dog whose prominent metabolites were 4',5'-dehydrobrimonidine and 5-bromo-6-guanidinoquinoxaline. 4. These results indicate extensive hepatic metabolism of brimonidine and provide evidence for aldehyde oxidase involvement in brimonidine metabolism. The species differences in hepatic brimonidine metabolism are likely related to the low activity of dog liver aldehyde oxidase. The principal metabolic pathways of brimonidine are alpha(N)-oxidation to the 2,3-dioxobrimonidine, and oxidative cleavage of the imidazoline ring to 5-bromo-6-guanidinoquinoxaline.

Acetates↗

PubMed1996

Cell cycle regulation of BRCA1 messenger RNA in human breast epithelial cells.

BRCA1 was originally isolated as a gene that conferred susceptibility to early-onset familial breast and ovarian cancers. The function and regulation of this gene is presently unknown. Northern blot analyses using probes that recognize different regions of the BRCA1 cDNA revealed the presence of at least two distinct mRNA species. In synchronized normal and immortalized human mammary epithelial cells, BRCA1 mRNA levels were high in exponentially growing populations, decreased upon growth factor withdrawal, and subsequently increased again in late G1 just prior to S-phase entry. BRCA1 mRNA levels were found to be dramatically reduced in senescent normal human mammary epithelial cells and in normal human mammary epithelial cells treated with transforming growth factor beta 1. When considered together, these data indicate that expression of BRCA1 mRNA is highly sensitive to changes in growth conditions in vitro. BRCA1 proteins with apparent molecular weights of M(r) 210,000, 185,000, 160,000, 135,000, and 85,000, respectively, were detected at varying levels in all breast epithelial cells examined. Further molecular characterization of the nature and function of the different BRCA1 mRNAs and proteins should increase our understanding of this gene in the etiology of human breast cancers.

Breast↗

PubMed1996

[Radiotherapy treatment of subfoveal retinal neovascularization: results after two years].

The treatment by radiotherapy (10 Grays) of subfoveal choroidal neovascular membranes is disappointing. Although after one year, 22% of cases had a positive result, after a mean follow up of 2.5 years only 14% of cases had a favourable outcome. The final visual acuity 30 months after treatment was the same as the one observed after 21 months of natural evolution. The well-defined nature of the subretinal new vessels, the presence of a pigment epithelial detachment and the occurrence of a vast hemorrhage were of bad prognosis.

Aged↗

PubMed1995

An STS-based map of the human genome.

A physical map has been constructed of the human genome containing 15,086 sequence-tagged sites (STSs), with an average spacing of 199 kilobases. The project involved assembly of a radiation hybrid map of the human genome containing 6193 loci and incorporated a genetic linkage map of the human genome containing 5264 loci. This information was combined with the results of STS-content screening of 10,850 loci against a yeast artificial chromosome library to produce an integrated map, anchored by the radiation hybrid and genetic maps. The map provides radiation hybrid coverage of 99 percent and physical coverage of 94 percent of the human genome. The map also represents an early step in an international project to generate a transcript map of the human genome, with more than 3235 expressed sequences localized. The STSs in the map provide a scaffold for initiating large-scale sequencing of the human genome.

Animals↗

PubMed1995

Hormone-dependent regulation of BRCA1 in human breast cancer cells.

BRCA1 mRNA and protein levels are regulated by the steroid hormones estrogen and progesterone in human breast cancer cells. BRCA1 mRNA and protein levels were significantly decreased in estrogen-depleted MCF-7 and BT20T cells and increased again after stimulation with beta-estradiol. The increase in BRCA1 expression upon stimulation with estrogen was not coordinated with the early induction of the estrogen-dependent pS2 gene but closely paralleled the delayed increase in the S-phase dependent marker cyclin A. T47-D cells deprived of steroid hormones and subsequently stimulated with progesterone also showed a delayed increase in BRCA1 mRNA expression. However, no change in BRCA1 protein was detected in these cells. When considered together, the data suggest that steroid hormones may affect BRCA1 expression indirectly by altering the proliferative status of the cells rather than acting directly on DNA sequences in the BRCA1 gene itself.

BRCA1 Protein↗

PubMed1995

Transcription factor IRF-2 exerts its oncogenic phenotype through the DNA binding/transcription repression domain.

The Interferon Regulatory Factors-1 and -2 (IRF-1 and IRF-2) play a transcriptional role in the regulation of the IFN-beta gene as well as other immunoregulatory genes. IRF-1 serves as a transcriptional activator whereas IRF-2 acts as an antagonistic transcriptional repressor. IRF-1 and IRF-2 also play opposing functional roles in cell growth regulation, and are implicated as a potential antioncogene and oncogene, respectively. To analyse the relationship between DNA binding/transcriptional repression and oncogenic transformation, NIH3T3 cells expressing C-terminal deletions of IRF-2 were established and assayed for transformation by saturation density analysis, anchorage independent growth in soft agar and tumor formation in nude mice. Cells expressing an IRF-2 protein of at least 160 N-terminal amino acids were transformed in vitro and tumorigenic in vivo, thus mapping IRF-2 oncogenic activity to its DNA binding/transcriptional repression domain. Overexpression of wild-type and truncated IRF-2 proteins resulted in reduced IFN-beta mRNA levels following induction by dsRNA. However, there was no effect of IRF-2 on IFN-beta inducibility by Sendai virus infection, suggesting the involvement of multiple IFN-beta induction pathways. In DNA binding assays, recombinant IRF-2 was found to preferentially bind to the IFN-beta PRDI site compared to IRF-1. These studies indicate that the transformed phenotype resulting from overexpression of IRF-2 may be due to constitutive engagement of the IRF-E recognition site, thus preventing DNA binding and transactivation of putative tumor suppressor genes by the IRF-1 anti-oncogene.

3T3 Cells↗

PubMed1995

Effects of cell cycle, wild-type p53 and DNA damage on p21CIP1/Waf1 expression in human breast epithelial cells.

In this study we examine the relationship between p21CIP1/Waf1 (CIP1), a 21 kDa protein that binds to and modulates the activity of several cyclin dependent kinases and expression of wild-type (WT) p53 in human breast epithelial cells. Basal CIP1 protein, but not CIP1 mRNA levels correlated well with expression of WT p53 in human breast epithelial cells. To obtain more direct evidence that WT p53 regulated the level of CIP1 protein, the Human Papilloma Virus (HPV) E6 protein was introduced into immortalized 184B5 breast cells. Residual WT p53 levels correlated well with CIP1 protein but not CIP1 mRNA levels in isolated clones of transfected cells. CIP1 protein was increased at early times after growth factor arrested cells were stimulated to proliferate. The rise in CIP1 protein was due to a concomitant increase in CIP1 mRNA levels in MCF10, but not in normal mammary epithelial cells. DNA damage induced by ionizing radiation resulted in a transient increase in WT p53 levels but a prolonged induction of CIP1 protein. The sustained increase in CIP1 protein 24 h after radiation could not be attributed to a concomitant increase in CIP1 mRNA levels. Although the half-life of the CIP1 protein was not altered following irradiation, a fourfold increase in the amount of radioactivity incorporated into CIP1 protein was detected. When considered together these data suggest that wild-type p53 affects CIP1 protein accumulation at a posttranscriptional level in human breast epithelial cells under different physiologic and stress conditions.

Breast↗

PubMed1995

Rejection of mouse melanoma elicited by local secretion of interleukin-2: implicating macrophages without T cells or natural killer cells in tumor rejection.

Tumor cells transduced with cytokine genes provide a model to study host-effector mechanisms involved in tumor rejection. Local IL-2 production within a tumor site mimics a specific helper-T-cell response, bypassing an immunization phase. Growth of mouse B16F10 melanomas transduced with interleukin-2 (IL-2) in syngeneic hosts were significantly delayed. IL-2-producing B16F10 cells were super-transduced with interferon-gamma to up-regulate expression of major-histocompatibility-complex (MHC) antigens. Expression of class-I- or class-II-MHC molecules did not augment tumor rejection of IL-2-secreting tumor cells. Rejection of IL-2-transduced B16F10 cells in syngeneic mice was unaffected by depletion of CD8+ T-cell and NK1.1+ natural-killer (NK) cell populations. Tumor rejection occurred in SCID mice even after depletion of NK1.1+ cells, confirming that T cells and NK cells were not required for tumor rejection. Histologic examination of sites of tumor rejection showed inflammation, characterized by infiltrates of macrophages, occasional neutrophils, and areas of necrosis. When mice were treated systemically with macrophage-colony-stimulating factor to expand monocyte pools, tumor rejection was significantly augmented further. This study shows that in situ IL-2 production can result in tumor rejection mediated by inflammatory events, possibly involving macrophages, and mimicking a delayed-type hypersensitivity (DTH) response even in the absence of T cells and NK cells. Furthermore, tumor rejection can be enhanced by systemic administration of a cytokine to expand potential inflammatory cell populations.

Animals↗

PubMed1995

Differential effects of prednisolone and indomethacin on zymosan-induced inflammation in a modified murine tissue-chamber model.

A tissue-chamber model of inflammation in mice has been modified and used to investigate the kinetics of zymosan-induced inflammatory mediators such as tumour necrosis factor alpha (TNF alpha), interleukin-1 beta (IL-1 beta) and prostaglandin E2 (PGE2). In addition, the influx of polymorphonuclear leukocytes (PMN) into the chamber fluid and the granuloma surrounding the chamber was measured by myeloperoxidase (MPO) activity using a new microtitre plate assay. TNF alpha and IL-1 beta reached a peak concentrations at 3 and 6 h respectively after zymosan injection. Intermediate high concentrations of IL-1 beta were observed until the end of the experiment at 72 h, but TNF alpha concentrations decreased from 24 h to biologically insignificant values. In contrast, exudate PGE2 and MPO activity increased up to 24 h after zymosan injection and remained high until 72 h. At 6 h after zymosan challenge, oral pre-treatment with prednisolone (3 to 30 mg/kg) dose-dependently reduced TNF alpha, IL-1 beta and PGE2 concentrations while indomethacin (0.3 to 3 mg/kg) significantly attenuated PGE2, slightly enhanced TNF alpha and had no effect on IL-1 beta concentrations in the exudate. Both drugs had similar potencies against exudate and tissue MPO activities. Prednisolone inhibited IL-1 beta at 72 h post-zymosan. Indomethacin was more potent than prednisolone against PGE2 (ID50 of< 0.3 versus 0.6 mg/kg). The data obtained confirm the usefulness and reliability of this model in evaluating the effects of anti-inflammatory agents on inflammatory mediators induced by zymosan.

Animals↗

PubMed1995

Mechanism of colonic permeation of inulin: is rat colon more permeable than small intestine?

BACKGROUND/AIMS: Colonic epithelium is considered to be relatively tight. The colonic "pore" diameter is 6 A; therefore, colonic epithelium has generally been considered to be impermeable to hydrophilic probes with a cross-sectional diameter of > 6 A. This study examined whether rat colon is permeable to inulin, a large hydrophilic macromolecule having a molecular weight of 5000 g/mol and a cross-sectional diameter of 15 A (hydration diameter, 20 A). METHODS: The colonic permeation of inulin (10 mumol/L) in vivo was investigated by perfusion of rat colonic segments. RESULTS: There was significant colonic permeation of inulin, but tissue retention of inulin was low. The net colonic flux of inulin was strongly dependent on net water flux, showing a strong solvent drag effect. Addition of 16,16-dimethyl prostaglandin E2 decreased water flux with a corresponding decrease in inulin flux; this process seemed to be mediated by 5'-cyclic adenosine monophosphate because both the phosphodiesterase inhibitor aminophylline and dibutyryl adenosine 5'-cyclic adenosine monophosphate decreased water and inulin flux in a parallel manner. Chenodeoxycholic and taurocholic acids decreased net mucosal-to-serosal water flux but increased inulin flux. The net colonic permeation rate of inulin was higher than the small intestinal permeation rate. CONCLUSIONS: Rat colon is permeable to inulin. The higher net colonic permeability may be caused by differences in mucosal surface, permselectivity, solvent drag effect, and differences in net water fluxes of the colon and small intestine.

16,16-Dimethylprostaglandin E2↗

PubMed1995

Modulation of intestinal chloride secretion at basolateral transport sites: opposing effects of cyclic adenosine monophosphate and phorbol ester.

BACKGROUND: Although intestinal Cl secretion is largely regulated by apical Cl channels, we have shown that net secretory capacity can be controlled at a basolateral site, the Na-K-2Cl cotransporter (NKCC). Phorbol myristate acetate (PMA) was found to inhibit both cyclic adenosine monophosphate (cAMP)-regulated Cl secretion and basolateral NKCC function in parallel but not apical Cl channels. Because inhibition of NKCC function could occur by reducing the number of membrane NKCC units, we examined the effect of PMA on cAMP-regulated NKCC function and number. METHODS: NKCC function and number were assessed in the human intestinal line HT29cl.19A by bumetanide-sensitive uptake of rubidium 86 and by specific binding of 3H-bumetanide. RESULTS: The cAMP agonist forskolin enhanced bumetanide-sensitive 86Rb uptake and doubled the number of NKCCs. PMA decreased both basal and cAMP-stimulated uptake in time- and dose-dependent fashion. In addition, PMA down-regulated basal NKCC number and abolished cAMP-induced NKCC recruitment. CONCLUSIONS: PMA opposes the action of cAMP on NKCC function by reducing both basal numbers of NKCCs and cAMP-induced recruitment of NKCCs and not by reducing ion translocation per NKCC. These data further emphasize the potential for modulation of intestinal Cl secretion at basolateral sites.

Biological Transport↗