Demonstration of a high affinity receptor for 1,25-dihydroxyvitamin D3 in rat pancreas

The existence of a high affinity receptor for 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) in rat pancreas was biochemically demonstrated in this study. In order to study the properties of this putative receptor, we took advantage of the analysis of low ionic strength chromatin-localized 1,25(OH)₂D₃ receptor. Using this method, the susceptibility of receptor protein to enzymatic degradation was so decreased, and the contamination by plasma vitamin D binding protein (DBP) component was so efficiently eliminated that a specific, saturable binding for 1,25(OH)₂D₃ could be demonstrated in the saturation analysis and the peak for the receptor was consistently apparent in the sucrose density gradient analysis. The equilibrium dissociation constant (Scatchard K_d) was found to be 3.7 ± 1.5 × 10^-10 (M), and the concentration of specific binding sites was calculated to be 1.22 ± 0.40 (fmol/mg protein). The number of specific binding sites in the rat pancreas was only 0.44% of that present in rat intestine (277 ± 19 (fmol/mg protein)) and 6.7% of that in rat kidney (18.1 ± 1.0 (fmol/mg)). However, when a correction is made for the 1,25(OH)₂D₃ receptor distribution in the tissues and expressed as the receptor concentration per receptor-containing cells, the rat pancreatic receptor level was calculated to be about 30% of the rat intestine. Sucrose density gradient sedimentation of this receptor yielded a value of 3.2 ± 0.1 (S) for the sedimentation coefficient and this peak was displaceable by a 100-fold excess of nonradioactive 1,25(OH)₂D₃. These data provide evidence for the presence of a specific 1,25(OH)₂D₃ receptor in mammalian pancreas, and we suggest, in conjunction with the facts that vitamin D₃ and its active metabolites play a physiological role on insulin secretion from rat pancreatic β-cells, that this receptor might be involved in the mechanisms of action of vitamin D₃ on insulin secretion from rat pancreas via a genomic effect.     

The effects of 17\-estradiol on chondrocyte differentiation are modulated by vitamin D3 metabolites

Both 17β-estradiol (17β) and the vitamin D metabolites, 1,25-(OH)₂D₃ (1,25) and 24,25-(OH)₂D₃ (24,25), regulate endochondral bone formation in vivo and in vitro. The effects of 17β are sex-specific and cell maturation-dependent. Similarly, the effects of 1,25 and 24,25 are cell maturation-dependent, with 1,25 affecting growth zone chondrocytes (GC) and 24,25 affecting resting zone chondrocytes (RC). This study examined whether the response of chondrocytes to 17β is altered after pretreatment with 1,25 or 24,25. Cells were isolated from the costochondral cartilage of male or female rats. Confluent, fourth-passage GC and RC cultures were pretreated with 1,25 or 24,25, respectively, for 24 or 48 h followed by treatment with 17β for an additional 24 h. At harvest, cell proliferation ([³H]-thymidine incorporation), differentiation (alkaline phosphatase specific activity [ALPase]), general metabolism ([³H]-uridine incorporation), and proteoglycan production ([³⁵S]-sulfate incorporation) were determined. 1,25 enhanced the inhibitory effect of 17β on [³H]-thymidine incorporation by female GC cells; in contrast, no effect was observed in GC cells obtained from male rats. When male RC cells were treated with 17β, [³H]-thymidine incorporation was inhibited; however, when these cells were pretreated with 24,25 for 48 h, 17β stimulated [³H]-thymidine incorporation 24,25 had no effect on 17β-dependent [³H]-thymidine incorporation by female RC cells. 17β stimulated ALPase in female GC cells, but had no effect on male GC cells. 1,25 pretreatment of female GC cells inhibited the stimulatory effect of 17β on ALPase, but had no effect on ALPase in male GC cultures. 17β had no effect on male RC cell ALPase and stimulated ALPase in female RC cells. This was not affected by pretreatment with 24,25. Pretreatment with 1,25 increased the basal level of sulfate incorporation only in female GC. No effect was found in RC cells. These results indicate that pretreatment of rat costochondral chondrocytes with vitamin D metabolites modulate the effect of 17β. Although the effect of vitamin D metabolites alone on these chondrocytes is maturation-dependent and not sex-specific, the influence of preincubation with vitamin D metabolites on the effect of 17β is hormone-specific, sex-specific, and maturation-dependent.     

Tissue-specific expression and regulation by 1,25(OH)2D3 of chick protein kinase inhibitor (PKI) mRNA

The heat-stable protein kinase inhibitor (PKI) protein is a specific and potent competitive inhibitor of the catalytic subunit of cAMP-dependent protein kinase (PKA). Previously, it has been shown that vitamin D status affects chick kidney PKI activity: a 5- to 10-fold increase in PKI activity was observed in kidneys of chronically vitamin D-deficient chicks and treatment with 1,25-dihydroxyvitamin D₃ (1,25[OH]₂D₃) in cultured kidney cells resulted in a 95% decrease in PKI activity. The authors have recently cloned the cDNA for chick kidney PKI and have used the coding sequence to study the regulation of PKI mRNA. Northern analysis showed the expression of two PKI messages, which are 2.7 and 3.3 kb in size. These mRNAs are expressed in brain, muscle, testis, and kidney, but not in pancreas, liver, or intestine. PKI mRNA steady-state levels are downregulated by 47% in kidneys from vitamin D-replete chicks as compared to vitamin D-deficient chicks. PKI mRNA levels in brain, muscle, and testis are not affected by vitamin D status. Treatment of primary chick kidney cultures treated with 10⁻⁷ M, 1,25(OH)₂D₃ for 24 h resulted in a 20–30% decrease in PKI mRNA. 1,25(OH)₂D₃ treatment does not affect the stability of PKI mRNA as determined by treatment of cell cultures with actinomycin D. This study shows that 1,25(OH)₂D₃ directly and tissue-specifically downregulates PKI mRNA in the chick kidney.     

1,25-二羟维生素D3对于哮喘大鼠及其肺泡巨噬细胞中VDUP1/TRX的影响

目的探讨1,25-二羟维生素D3（1,25-dihydroxyvitamin D3,1,25（OH）2D3）对哮喘大鼠支气管肺泡灌洗液（bronchoalveolar lavage fuluid,BALF）中维生素D上调蛋白1（vitamin D up-regulated protein 1,VDUP1）和硫氧还蛋白（thioredoxin,TRX）表达及气道炎症的影响。方法将28只Wistar大鼠随机分为4组,以卵白蛋白（ovalbumin,OVA）诱导哮喘发作,并给予1,25（OH）2D3和地塞米松干预,同时设对照组。测定BALF中IL-4和IL-10水平,细胞总数和肺组织病理变化。同时提取7只哮喘模型大鼠BALF中的巨噬细胞,体外给予1,25（OH）2D3干预。用逆转录-聚合酶链反应检测肺组织及BALF中巨噬细胞表达VDUP1和TRX的水平。结果 1,25（OH）2D3治疗组BALF中细胞总数及嗜酸粒细胞计数和IL-4水平降低,IL-10水平增高。肺组织及肺泡巨噬细胞中VDUP1和TRX表达增加。结论给予哮喘大鼠1,25（OH）2D3可抑制气道炎症,增加TRX和VDUP1的表达,两者可作为哮喘氧化应激的监测指标。     

Preferential accumulation in vivo of 24R,25-dihydroxyvitamin D(3) in growth plate cartilage of rats

Vitamin D₃ is metabolized in vivo through 25-(OH)D₃ (25D) to both 1α,25-(OH)₂D₃ (1,25D) and 24R,25-(OH)₂D₃ (24,25D). Whereas it is assumed that this metabolism occurs primarily in the kidney, recent studies show that there are extrarenal 1α-and 24R-hydroxylase activities as well, and in chondrocytes, these enzymes are regulated by hormones and growth factors. Furthermore, chondrocytes from the resting zone of growth plate cartilage are a target cell population for 24,25D action, suggesting that this vitamin D metabolite may be targeted to this tissue in vivo. To test this hypothesis, 30 normal male Sprague Dawley rats (120 ±20 g) were divided into three groups of eight animals each, and a control group of six animals, and fed ad libitum for 2 wk, a standard rat chow (Teklad LM-485), which contained 3 IU vitamin D₃/g. The rats were then injected im daily at 9:00am, for 4 consecutive d, with 0.1 mL of either [³H]-25D, [³H]-1,25D or [³H]-24,25D. Each dose contained 13 pmol of hormone (0.36 μCi/dose). The distribution of these metabolites was assessed in tibial bone (B) following ablation of the bone marrow, articular cartilage from the tibia (AC), costochondral growth plate cartilage (GC), serum (S), small intestine (I), and kidney (K). The use of high specific activity tritiated vitamin D metabolites facilitated determining tissue localization and further metabolism without perturbation of the body pools of each major metabolite. Accumulation of [³H]-1,25D or [³H]-24,25D in each tissue was compared to circulating serum levels. In rats dosed with [³H]-25D, the tissue:serum ratios for 1,25D were 4.1 (AC), 35.4 (GC), 1.3 (B), 0.7 (K), and 3.0 (I); and tissue:serum ratios for 24,25D were 1.6 (AC), 9.9 (GC), 0.04 (B), 0.2 (K), and 0.4 (I). In rats dosed with [³H]-24,25D alone, GC was the only tissue to accumulate the administered metabolite at a concentration significantly higher than that of serum. Similarly, in rats dosed with [³H]-1,25D alone, GC was the only tissue to accumulate 1,25D at a concentration higher than that of serum. These results demonstrate, for the first time, that under in vivo conditions, GC specifically accumulates 24,25D and 1,25D. This suggests that growth plate may be a target organ for these two hormones.     

三种剂量维生素D3结合高脂饲料建立大鼠动脉粥样硬化模型的比较

目的 探讨维生素D3结合高脂饲料建立大鼠动脉粥样硬化模型的方法.方法 健康雄性Wistar大鼠40只随机平均分为四组:对照组、模型1组、模型2组、模型3组.对照组喂常规饲料,模型组喂高脂饲料.模型1组在造模前腹腔注射维生素D370万IU/kg,分4次每隔两天注射;模型2组在造模前注射60万IU/kg,造模后第3、6、9周分别注射10万IU/kg;模型3组在造模前和造模后第3、6、9周分别注射60万IU/kg;喂养12周后比较各组动物体重、血脂和主动脉病理变化.结果 12周后,模型组各组体重较对照组明显下降(P＜0.01),其中模型3组体重下降最显著且死亡率最高;模型组各组的血清总胆固醇和低密度脂蛋白胆固醇与对照组比较均明显升高(P＜0.01);模型1、2、3组造模成功只数分别为3只、8只和5只.结论 高脂饲料结合造模前腹腔注射维生素D360万IU/kg,造模后第3、6、9周各补充10万IU/kg是比较有效的制备动脉粥样硬化大鼠模型方法.     

Response of jejunal phosphate absorption to 1,25-dihydroxyvitamin D(3) stimulationin vivo in young X-linked hypophosphatemic (Hyp) mice

YoungHyp mice malabsorb phosphate from the jejunum at 4 weeks of age. This has been attributed to both low plasma levels of 1,25-dihydroxyvitamin D and to intestinal resistance to stimulation by 1,25-dihydroxyvitamin D. To differentiate between these two hypotheses, 4 week old normal andHyp mice were treated with 0, 17, 50, or 150 ng/kg/day of 1,25-dihydroxyvitamin D₃ by Alzet osmotic mini pumps (n=10–12/group). After 4 days, the jejunum was isolated by sutures and 0.5 ml 2 mM Na₂HPO₄ in 150mm NaCl with 1.0 μCi³²PO₄ was injected into the lumen. After 8 min, plasma, jejunal tissue and lumenai contents were measured for³²P content. Absorption was measured as counts removed from the lumen. Both normal andHyp mice responded to the 1,25-dihydroxyvitamin D₃ with increased absorption, increased tissue³²P and increased plasma³²P.Hyp mice responded less than normal mice to the 50 ng/kg/day dose in plasma³²P levels (significant dose by genotype interaction,P<0.05). Plasma was pooled by genotype and dose for the measurement of plasma 1,25-dihydroxyvitamin D. This yielded 13 samples (7 normal and 6Hyp). Absorption of³²P (r=0.75, p=0.002) and jejunal tissue content of³²P (r=0.66, p=0.02) were correlated to plasma 1,25-dihydroxyvitamin D. Analysis of covariance revealed a significant difference in phosphate absorption between normal andHyp mice (p=0.02). In conclusion, there is a partial resistance of intestinal phosphate absorption to 1,25-dihydroxyvitamin D stimulation.     

Age and gender effects on 1,25-dihydroxyvitamin D3-regulated gene expression

Several factors involved in regulation of bone mineral metabolism were compared in male and female Fischer 344 rats of different ages (1, 2.5, 6, and 18 months). Plasma 1,25-(OH)₂D₃ concentrations decreased with age in rats of both genders. Abundance of calbindin-D_28K and its mRNA in kidney and calbindin-D_9K and its mRNA in duodenum also decreased with age in both male and female rats. Renal 24-hydroxylase activity and 24-hydroxylase mRNA content were elevated significantly in 18-month-old males and females, compared with younger ages. These data suggest that increased renal catabolism of 1,25-(OH)₂D₃ may be responsible for low plasma 1,25-(OH)₂D₃ concentrations observed in older animals. Plasma PTH and 1,25-(OH)₂D₃ concentrations, renal 24-hydroxylase enzyme activity and 24-hydroxylase mRNA content, duodenal 24-hydroxylase mRNA abundance, and duodenal calbindin-D_9K and calbindin-D_9K mRNA content were greater in males than in females at 2.5 months of age. Lower plasma 1,25-(OH)₂D₃ concentrations in females seem to explain observed gender differences in expression of 1,25-(OH)₂D₃-stimulated genes. The combined effects of these gender differences at ages when peak bone density is being developed may contribute to the greater incidence of osteoporosis in females than in males.     

Treatment of resting zone chondrocytes with bone morphogenetic protein-2 induces maturation into a phenotype characteristic of growth zone chondrocytes by downregulating responsiveness to 24,25(OH)2D3 and upregulating responsiveness to 1,25-(OH)2D3

To determine if bone morphogenetic protein-2 (BMP-2) can induce the endochondral maturation of resting zone (RC) chondrocytes, confluent fourth-passage cultures of these cells were pretreated for 24, 36, 48, 72, or 120 h with recombinant human BMP-2. At the end of pretreatment, the media were replaced with new media containing 10⁻¹⁰–10⁻⁸ M 1,25-(OH)₂D₃ or 10⁻⁹–10⁻⁷ M 24,25-(OH₂)D₃, and the cells incubated for an additional 24 h. This second treatment was chosen, because prior studies had shown that the more mature growth zone (GC) chondrocytes and RC cells respond to 1,25-(OH)₂D₃ and 24,25-(OH)₂D₃ in distinctly different ways with respect to the parameters examined. The effect of BMP-2 pretreatment on cell maturation was assessed by measuring alkaline phosphatase specific activity (ALPase). In addition, changes in matrix protein production were assessed by measuring collagen synthesis, as well as [³⁵S]-sulfate incorporation into proteoglycans. When RC cells were pretreated for 72 or 120 h with BMP-2, treatment with 1,25-(OH)₂D₃ caused a dose-dependent increase in ALPase specific activity and collagen synthesis, with no effect on proteoglycan sulfation. RC cells pretreated with 1,25-(OH)₂D₃ responded like RC cells that had not received any pretreatment. RC cells normally respond to 24,25-(OH)₂D₃; however, RC cultures pretreated for 72 or 120 h with BMP-2 lost their responsiveness to 24,25-(OH)₂D₃. These results indicate that BMP-2 directly regulates the differentiation and maturation of RC chondrocytes into GC chondrocytes. These observations support the hypothesis that BMP-2 plays a significant role in regulating chondrocyte maturation during endochondral ossification.     

Age-related increase of prostaglandin D2 synthase concentration and glycation in ovine cerebrospinal fluid

Prostaglandin D₂ synthase (PGDS) is a glycoprotein that is exclusively brain derived and is one of the most abundant proteins in the cerebrospinal fluid (CSF). Due to its high CSF specificity, it can be used as a tool for the diagnosis of central nervous system (CNS) disorders. However, several studies have yielded contradictory CSF PGDS concentrations in various CNS neurodegenerative disorders. Sheep CSF samples from different ages were used in this study and 2-dimensional electrophoresis (2-DE) was applied in PGDS identification and concentration calculation. SYPRO Ruby Protein Gel Stain was the staining method used to stain the 2-DE gel protein spots. Pro-Q Emerald 488 Staining for Glycoproteins was used for the staining of glycoproteins. A total of nine PGDS isoforms were identified and CSF total PGDS concentration was calculated to increase linearly by 44% from young (0.9323 ± 0.0637 mg dL⁻¹) to old (1.3669 ± 0.0558 mg dL⁻¹). However, the proportion of CSF total PGDS as a percentage of CSF total protein was discovered to decrease exponentially with age. This was due to the influence of larger age-related increase in CSF albumin concentration (>200% from young to old) as albumin is the most abundant protein in the CSF (>60% of total CSF proteins). Active deglycosylation was not observed in PGDS isoforms during healthy ageing. Some PGDS isoforms were observed to have age-related increase in glycation. These findings suggest that CSF PGDS concentration is increased during healthy ageing and must be taken into consideration when using PGDS as a potential biomarker in diagnosing CNS neurodegenerative disorders. Whether age-related increase in the glycation of some CSF PGDS isoforms will result in detrimental effects on the PGDS protein function needs further investigations.     

Autocrine Regulation of TGF β Expression in Adult Cardiomyocytes

G. Taimor, K.-D. Schlüter, K. Frischkopf, M. Flesch, S. Rosenkranz and H. M. Piper. Autocrine Regulation of TGF β Expression in Adult Cardiomyocytes. Journal of Molecular and Cellular Cardiology (1999)31 , 2127–2136. As shown before, TGF β acts in an autocrine manner on the induction of hypertrophic responsiveness to β -adrenoceptor stimulation in cultured ventricular cardiomyocytes of adult rat. We now investigated how TGF β expression and activation is regulated in these cultures and how β -adrenoceptor stimulation influences TGF β -mRNA expression. It was found that freshly isolated cardiomyocytes secrete latent TGF β in the culture medium. Supplementation of the cultures with 20% FCS resulted in activation of the secreted TGFβ to 4.1±0.2 ng/ml active TGF β after 6 days. Presence of the protease inhibitor aprotinin (50μ g/ml) reduced TGF β activity by 44±5% (n=5, P<0.05). In cultures supplemented with 5% FCS, TGF β was not activated. Active TGF β downregulated its mRNA-expression: after 6 days TGF β₁-mRNA was reduced to 55.1±11.0%, TGFβ₂ -mRNA to 30.1±16.5%, and TGF β₃-mRNA to 0.3±0.4% in 20% FCS-cultures as compared to their expression in freshly isolated cells (n=4, P<0.05). TGFβ -mRNA expression did not change in cultures without active TGF β. Isoprenaline (1 μ m) increased TGF β₁-mRNA only in cultures which had been pre-exposed to active TGF β. This effect was also seen when hearts from normal mice were compared with hearts from transgenic mice overexpressing TGFβ₁ : only in hearts from transgenic animals perfusion with isoprenaline increased TGFβ₁ -mRNA. In conclusion, isolated cardiomyocytes release latent TGF β, which is activated by external proteases. Active TGF β downregulates its own mRNA expression. Preexposure to TGF β is necessary for a β -adrenoceptor-mediated increase in TGF β₁-mRNA in cardiomyocytes.     

Adenosine A2A and A2B receptors work in concert to induce a strong protection against reperfusion injury in rat hearts

We aimed to test if stimulation of both adenosine A_2A and A_2B receptors is required to produce an effective cardioprotection against reperfusion injury. Isolated rat hearts were subjected to 30-min regional ischemia followed by 2 h of reperfusion. The adenosine A₁/A₂ receptor agonist 5′-(N-ethylcarboxamido) adenosine (NECA) given at reperfusion reduced infarct size, an effect that was reversed by both the adenosine A_2A antagonist SCH58261 and the A_2B antagonist MRS1706. The A_2B agonist BAY 60-6583 but not the selective A_2A agonist CGS21680 reduced infarct size. Interestingly, a combination of BAY 60-6583 and CGS21680 further reduced infarct size. These results suggest that both A_2A and A_2B receptors are involved in NECA's anti-infarct effect at reperfusion. NECA attenuated mitochondrial swelling upon reperfusion and this was blocked by both SCH58261 and MRS1706, indicating that activation of A₂ receptors with NECA can modulate reperfusion-induced mitochondrial permeability transition pore (mPTP) opening. In support, NECA also prevented oxidant-induced loss of mitochondrial membrane potential (ΔΨ_m) and matrix Ca²⁺ overload in cardiomyocytes via both the A₂ receptors. In addition, NECA increased mitochondrial glycogen synthase kinase-3β (GSK-3β) phosphorylation upon reperfusion and this was again blocked by SCH58261 and MRS1706. In conclusion, A_2A and A_2B receptors work in concert to prevent reperfusion injury in rat hearts treated with NECA. NECA may protect the heart by modulating the mPTP opening through inactivating mitochondrial GSK-3β. A simultaneous stimulation of A_2A and A_2B receptors at reperfusion is required to produce a strong cardioprotection against reperfusion injury.     

1,25-Dihydroxy-vitamin D3 (calcitriol)-dependent protein phosphorylation in rat duodenum: effects of ageing

We have examined the ability of 1,25(OH)₂-vitamin D₃ [1,25(OH)₂D₃; calcitriol], the hormonal form of vitamin D₃, to stimulate the phosphorylation of proteins in rat duodenum from young (3 months) and aged (22–24 months) rats. Brief (30 s) exposure of duodenum preincubated with ³²P-orthophosphate to the hormone increased the labeling of whole tissue proteins, an effect that was greatly diminished in aged animals. The response was dose-dependent, with maximal stimulation achieved at 1 nM calcitriol (+113% and +10% for young and aged rats, respectively). Phosphoproteins were resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and identified by autoradiography. The hormone potentiated the phosphorylation predominantly on serine, threonine, and tyrosine residues of five acidic proteins of relative molecular masses of 66, 48, 45, 28, and 16 kDa. Moreover, the effects of calcitriol were exerted at the membrane level and varied as a function of exposure time. Direct treatment of purified basal lateral membranes for 30 s with the hormone (1 nM) stimulated the incorporation of ³²P of a 66kDa protein by 75% and of a 48 and 45kDa proteins by 60%. The effects of the hormone on basal lateral membrane protein phosphorylation were suppressed by the PKA, PKC, and tyrosine kinase inhibitors, Rp-cAMPS, bisindolylmaleimide, and genistein, respectively. In basal lateral membrane isolated from old animals, only minor changes in calcitriol–induced protein phosphorylation of the 66-kDa protein were observed. Taken together, these results suggest that calcitriol modulates duodenal membrane protein phosphorylation, at least in part through PKA, PKC, and tyrosine kinases, and that this mechanism is severely altered with ageing. The identity of the proteins whose phosphorylation was stimulated by calcitriol and their physiological role is currently under investigation.     

The Long and Short of β2-agonists

For patients whose asthma is not adequately controlled with inhaled corticosteroid (ICS) therapy alone, increasing the dose of ICS or the addition of a long-acting β₂-agonist is recommended. Greater improvements in lung function are achieved with the addition of a long-acting β₂-agonist to ICS therapy, rather than doubling the dose of ICS. Formoterol and salmeterol have a similarly long duration of effect (up to 12 h). However, as a result of their different chemical structures, there are marked pharmacological differences in the mechanism of action which affect their speeds of onset. These differences amount to a more rapid onset of effect for formoterol compared with salmeterol. Long-acting β₂-agonists appear to be well tolerated at elevated doses. These two features (tolerability at high doses and rapid onset of effect) support the use of formoterol as a reliever medication in addition to use in maintenance therapy. The long-acting β₂-agonists can be considered as beneficial additions to ICS therapy for the management of moderate-to-severe asthma.     

HCV infection in haemodialysed patients: A role for serum IL-10 and TGF-β1 in liver damage?

BACKGROUND: Hepatitis C virus (HCV) infection is often clinically silent in haemodialysed (HD) patients and their immune response may modulate liver damage in HCV infection. IL-10 and TGF-beta1 could play a role in this setting as, IL-10 down-regulates hepatic fibrosis, while TGF-beta1 is a pro-fibrotic cytokine. AIM: To evaluate the role of IL-10 and TGF-beta1 in HD/HCV+ patients. PATIENTS: 71 HD/HCV+ patients (58 with normal [HD/HCV-N] and 13 with high serum transaminases [HD/HCV-H]), 40 non-uremic patients with chronic hepatitis C (HCV+), 56 HD anti-HCV- patients and 20 healthy volunteers (H). METHODS: IL-10 and TGF-beta1 serum levels were assessed using ELISA tests. Liver histology was assessed by Ishak's score. RESULTS: IL-10 serum levels were significantly higher in HD patients, both HCV+ (3.7+/-0.4 pg/ml; p<0.01) and HCV- (3.8+/-0.8 pg/ml; p<0.05) than in non-uremic HCV patients (2.3+/-0.4 pg/ml). Among the HD/HCV+ patients, IL-10 serum levels were similar in HD/HCV-N and in HD/HCV-H patients. Among the HD/HCV+ patients, IL-10 serum levels were similar in those with moderate histological damage compared to those with mild damage. TGF-beta1 serum levels were significantly lower in HD patients, both HCV+ (4.6+/-0.9 ng/ml) and HCV- (6.0+/-0.9 ng/ml) than in non-uremic HCV+ patients (8.1+/-1.1 ng/ml; p<0.001 and p<0.01, respectively), but similar to the values found in H (5.3+/-0.9 ng/ml; p=n.s.). No correlation was seen between IL-10 and TGF-beta1 serum levels in any of the groups considered. CONCLUSIONS: Patients on haemodialysis treatment to have high levels of IL-10, which remain high even when patients are anti-HCV+, whereas the opposite is true of TGF-beta1. The cytokine pattern observed in HD patients is compatible with the hypothesis explaining the relatively benign evolution of HCV-related liver disease in HD patients, and has a pathophysiological role.     

Phosphate Transport Adaptation in Rat Jejunum and Plasma Level of 1,25-Dihydroxyvitamin D3

Intestinal absorption of inorganic phosphate (Pi) increases in response to a reduction in the dietary supply of Pi. In this work this adaptive response has been characterized in jejunal brush border membrane vesicles and studied in temporal relationship with the change in the plasma level of 1,25(OH)2D₃. The results indicate that in rat jejunal brush border membrane vesicles the activity of the sodium-dependent Pi transport system is stimulated by a low Pi diet. This adaptive response was the result of an increase in the V_max and a reduction in the K_m of the cotransport system. This change in Pi transport was correlated with an increase in the circulating level of 1,25(OH)2D₃ in a time-related fashion. In conclusion, these results are consistent with the notion that Pi restriction leads to an increase in Pi transport activity in the luminal membrane of the intestine. A time course study suggests that the elevation in plasma 1,25(OH)2D₃ might be involved in the adaptation of the intestinal Pi transport system to Pi restriction.