A high concentration of dopamine preferentially permitted release of newly synthesized prolactin

We used continuous labelling ([3H]leucine) of cultured adenohypophysial cells to investigate the relationship between the storage and release of newly synthesized and stored prolactin in response to dopamine (1 mumol/l) and thyrotropin-releasing hormone (TRH) (0.1 mumol/l) challenge. Newly synthesized prolactin was identified by the tritium radiation activity incorporated in prolactin. A maximal dose of dopamine (1 mumol/l) could not completely block prolactin release from a primary culture of lactotrophs. During 3 h of continuous labelling under maximal dopaminergic inhibition, newly synthesized prolactin was released which was of a significantly higher specific activity than control groups. In contrast, TRH stimulation produced results consistent with previous observations of the release of predominantly old, stored hormone. However, the absolute amount of the newly synthesized prolactin was increased by the TRH administration, and the increased release of the newly synthesized prolactin could be accounted for by increased levels of synthesis. Our results are consistent with the concept of the existence of a regulated route and a dopamine-insensitive constitutive route of prolactin release which predominantly encompasses newly synthesized hormone. However, the possibility that cellular heterogeneity or that non-dopaminergic prolactin-release inhibiting factor(s) (PIF) is responsible for this observed release cannot be ruled out.     

罗格列酮对高糖环境下内皮祖细胞增殖和凋亡的影响

目的 观察高糖环境对内皮祖细胞(EPC)的损伤作用及罗格列酮对其的保护作用.方法 将健康志愿者骨髓单个核细胞接种于包被有人纤维黏连蛋白的培养板中,培养7天后获得正分化的EPC.贴壁细胞随机分为对照组、高糖组和高糖加罗格列酮组,分别于24h、96h后MTT测定3组细胞增殖功能,PI单染法检测其凋亡率.结果 高糖作用24h促进EPC的增殖能力,与对照组比,其OD值更大(P<0.05),且凋亡率没有明显增加(P>0.05).96h后,高糖明显抑制其增殖能力,OD值低于对照组(P<0.05),且凋亡率明显增加(P<0.01).罗格列酮干预后OD值比高糖组明显增加(P<0.05),且凋亡率明显降低(P<0.01).结论 长期高糖作用可抑制EPC增殖功能,使凋亡率增加;罗格列酮可能保护高糖环境下EPC的增殖能力并降低凋亡率.     

Chronic ethanol reduces nicotine-induced dopamine release in PC12 cells

Background: There is a high correlation between alcohol and nicotine use; that is, alcohol use is associated with high levels of smoking. One important aspect of nicotine addiction appears to be the activation of nicotinic acetylcholine receptors on dopaminergic neurons projecting from the ventral tegmental area to the nucleus accumbens. The release of dopamine from these neurons is thought to mediate, at least in part, the reward of nicotine consumption. If chronic alcohol consumption affects the amount of dopamine released in response to nicotine, it could contribute to the high level of smoking seen in alcoholics. Methods: We have used an in vitro model system to study the effects of chronic ethanol exposure on acute nicotine‐induced dopamine release and the withdrawal from ethanol. A pheochromocytoma cell line (PC12 cells) was exposed to ethanol for periods of 3 to 96 hr, followed by a 5 min exposure to nicotine. Dopamine released in response to nicotinic stimulation was measured by high‐pressure liquid chromatography. Results: Exposure of PC12 cells to chronic ethanol resulted in a time‐ and dose‐dependent inhibition of nicotine‐induced dopamine release. A moderate dose of ethanol (50 mM) resulted in a significant reduction in as little as 3 hr. The cells demonstrated a form of cross‐tolerance in that they showed diminished response to nicotine even though they had never been exposed to nicotine. After ethanol was withdrawn from the cells after a chronic exposure (96 hr), dopamine release slowly returned to normal levels but demonstrated a significant period of “overshoot” or hyperresponsiveness between 24 and 48 hr after withdrawal. Conclusions: These results show that chronic ethanol exposure decreases nicotine‐induced dopamine release and demonstrate a period of hyperresponsiveness during withdrawal from ethanol. These studies suggest potential interactions between chronic ethanol and nicotine that may provide insight into such phenomena as cross‐tolerance and increased use of nicotine by alcoholics.     

罗格列酮对高糖诱导下大鼠肾小球系膜细胞增殖及细胞周期的影响

以大鼠肾小球系膜细胞株(HBZY-1)为靶细胞,观察不同浓度不同时间罗格列酮(RSG)对高糖培养的系膜细胞的作用,发现RSG在一定范围内以剂量和时间依赖关系抑制高糖诱导的肾小球系膜细胞增殖,阻止系膜细胞由G1期进入S期,并诱导细胞凋亡。RSG有效减轻了高糖诱导的肾小球系膜细胞的病理损伤。     

氟伐他汀对高糖环境中肾小球系膜细胞胞外信号调节激酶活性的影响

高糖环境中SD大鼠肾小球系膜细胞胞外信号调节激酶（ERK）活性、转化生长因子β1（TGF—β1）mRNA水平升高，Ⅳ型胶原含量增多，氟伐他汀可抑制上述反应，提示ERK通路的激活参与糖尿病肾病的发生、发展，氟伐他汀可能通过抑制ERK通路活化及TGF—β1表达发挥非降脂相关的肾保护作用。     

β-连环蛋白在高糖诱导的内皮细胞损伤中的作用

内皮细胞功能紊乱被认为是高糖诱导血管并发症的始动因素和加重的基础。Wnt／β-连环蛋白信号途径在内皮细胞增生和凋亡的调控上起着重要作用,这条信号通路关键调节靶点是胞浆中β-连环蛋白的水平,它决定了Wnt靶基因的活化水平。当内皮细胞处于高糖环境中,β-连环蛋白减少,Wnt信号减弱,内皮细胞抗凋亡能力下降,增殖受到抑制,从而导致血管并发症。除此以外,在高糖作用下,β-连环蛋白介导的内皮细胞间黏附连接的破坏将导致内皮通透性增高,使蛋白质等大分子物质漏出血管外,同样造成血管功能紊乱。     

Effect of glucose and insulin on immunoreactive endothelin-1 release from cultured porcine aortic endothelial cells

We measured the release of immunoreactive endothelin-1 (IR-ET-1) by cultured porcine aortic endothelial cells under normoglycemic (5.5 mmol/L) and hyperglycemic (27.5 and 55 mmol/L) conditions. Compared with cells incubated in the presence of a normal glucose concentration, cells incubated in 27.5 mmol/L glucose medium released 52% less IR-ET-1, and those incubated in 55 mmol/L glucose medium released 54% less IR-ET-1. The observed effects of elevated glucose on IR-ET-1 release were both sugar-specific and not due to increased osmolarity. Fetal calf serum (FCS)-stimulated IR-ET-1 release in the presence of elevated glucose was also less than that in the presence of a normal glucose concentration. In addition, the effects of two hormones, insulin and insulin-like growth factor 1 (IGF-1), on IR-ET-1 release were examined. Both insulin and IGF-1 dose-dependently stimulated IR-ET-1 release. Twenty micrograms/mL insulin and 10(-8) mol/L IGF-1 increased IR-ET-1 release by 38% and by 44%, respectively. These results indicate that hyperglycemic condition results in reduction of IR-ET-1 release from cultured porcine aortic endothelial cells and that insulin and IGF-1 stimulate its release. The possible relevance of these observations to physiological regulation of ET-1 release in vivo and pathological processes in diabetes remains to be established.     

高糖对人脐静脉内皮细胞内皮抑素表达的影响

目的 研究高糖对人内皮细胞内皮抑素(ES)mRNA及蛋白表达水平的影响及其意义.方法 培养人脐静脉内皮细胞(HUVECs),分为正常糖(5.6mmol/L)对照组,高糖(11.2、22.4mmol/L)组.培养24、48、72、96h后,收集各组不同作用时间点细胞,用RT-PCR法检测ES mRNA表达水平,Western blot法检测ES蛋白的表达.结果 高糖对HUVECs中ES mRNA和蛋白表达水平的影响是双相的:短时间内起促进作用,具有时间依赖性;随作用时间延长转为抑制作用,22.4mmol/L糖培养HUVECs 96h时组ES mRNA和蛋白表达水平较对照组明显降低(P<0.05).结论 糖尿病(DM)慢性病程中,ES表达的降低可能与DM血管病变的发生有关.     

Effect of glucose concentration on foam cell formation in THP-1 cells.

We investigated whether a high glucose condition could affect cholesterol ester (CE) synthesis and accumulation of cholesterol in arterial wall cells by using the human monocytic cell line THP-1. After 24-hour PMA treatment, cells were grown in control (200 mg/dl of glucose) or high glucose concentration (400, 600, 800, or 1,600 mg/dl) medium for 6 days. CE synthesis was then investigated in cells incubated with 50 microg/ml of native, glycated, acetylated, or oxidized LDL. Cells grown in 400 mg/dl of glucose showed a significant increase of CE synthesis regardless of whether they were incubated with native, glycated or oxidized LDL, compared with cells grown in 200 mg/dl of glucose. In parallel with the studies of CE synthesis, the intracellular accumulation of CE also increased in cells grown in 400 mg/dl of glucose when incubated with oxidized LDL (50 microg/ml), compared with that in cells grown in 200 mg/dl of glucose. The amount of oxidized LDL associated with cells grown in 400 mg/dl of glucose was markedly higher than that in cells grown in 200 mg/dl of glucose. This suggests that there is an optimal glucose concentration (400 mg/dl) which increases the number of some scavenger receptors (receptors for oxidized LDL) expressed on cells, and might increase and stimulate CE synthesis, resulting in intracellular accumulation of CE in macrophage. A high blood glucose concentration could change the metabolism of arterial wall cells and play an important role in the pathogenesis of vascular complications of diabetes mellitus.     

胰腺星状细胞对高糖诱导的胰岛β细胞凋亡的影响

目的 观察胰腺星状细胞对高糖诱导的大鼠胰岛β细胞株Ins-1细胞活力及凋亡的影响,探索胰腺星状细胞在糖尿病胰岛功能衰竭进程中的作用.方法 构建Ins-1及胰腺星状细胞共培养系统,细胞分为Ins-1对照组、Ins-1高糖组(25 mmol/L葡萄糖)、Ins-1高渗组(25 mmol/L甘露醇)、共培养对照组、共培养高糖组(25 mmol/L葡萄糖)、共培养高渗组(25 mmol/L甘露醇).24 h后采用流式细胞法分析Ins-1细胞早期凋亡水平,48 h后分别采用嚷唑蓝(MTT)法和4,6-二氨基-2-苯基吲哚(DAPI)染色法检测细胞活力及凋亡细胞形态.使用单因素方差分析进行数据统计.结果 Ins-1高糖组与Ins-1对照组比较,Ins-1细胞凋亡率显著增加(分别为7.93%±0.41%、3.73%±0.35%,F=55.68,P<0.05);共培养高糖组与共培养对照组比较,Ins-1细胞凋亡率显著增加(分别为11.73%±1.20%、5.03%±0.41%,F=55.68,P<0.05).Ins-1高糖组与Ins-1对照组比较,细胞活力明显下降(分别为2.28±0.13、2.85±0.31,F=97.75,P<0.05);共培养高糖组与共培养对照组比较,细胞活力明显下降(分别为0.62±0.06、1.29±0.19,F=97.75,P<0.05).共培养对照组、共培养高糖组、共培养高渗组与Ins-1对照组、Ins-1高糖组、Ins-1高渗组比较,Ins-1细胞凋亡率显著增加(分别为5.03%±0.41%、3.73%±0.35%;11.73%±1.20%、7.93%±0.41%;7.60%±0.72%、5.60%±0.40%;F=55.68,P<0.05),细胞活力明显下降(分别为1.29±0.19、2.85±0.31;0.62±0.06、2.28±0.13;0.65±0.07、2.35±0.12;F=97.75,P<0.05),并可见凋亡细胞典型形态特征.结论 高糖、胰腺星状细胞可致大鼠胰岛β细胞Ins-1活力下降,凋亡增加;胰腺星状细胞可促进高糖诱导的胰岛β细胞凋亡.     

Effect of dopamine on parathyroid hormone release during surgery

There is much evidence that dopamine (DA) may play an important role in modulating parathyroid gland function. DA stimulates parathyroid hormone (PTH) secretion in cattle, which increases ionized calcium, but is without such effect on humans under normal physiological conditions. Ionized calcium plays a major role in muscle contraction including myocardial contractility. Therefore, we studied the PTH response to infusion of DA (4 micrograms/kg/min) under pathophysiological states during two different types of surgery; gastrectomy with halothane anesthetics and open heart surgery with high-dose fentanyl anesthetics. There was no change in PTH concentration, as measured by radioimmunoassay, in patients undergoing gastrectomy, although infusion of DA in these patients was effective in lowering the prolactin levels. However, plasma PTH concentration significantly increased where DA was applied (4 micrograms/kg/min) in patients undergoing open heart surgery. These results suggest that DA may stimulate PTH secretion by an indirect mechanism in humans under pathophysiological states, although details of the mechanism are unknown, and that there is the possibility that DA would indirectly regulate the levels of electrolytes such as ionized calcium and phosphate in patients undergoing open heart surgery mediated by elevation of PTH.     

Decrease in insulin binding to aortic endothelial cells cultured with high glucose concentration

We studied the effects of glucose on specific insulin binding to cultured endothelial cells from the bovine aorta. We cultured the cells in Dulbecco's modified Eagle's medium, containing 100 or 300 mg/dl glucose or 100 mg/dl glucose plus 200 mg/dl mannitol. We added 125I-insulin to monolayers of these cells and counted the radioactivity resulting. Specific insulin binding increased with time and dosage. Maximal binding resulted from 0.17 nM 125I-insulin being incubated for 30 min at 37 degrees C, and amounted to 0.35% per 10(5) cells being bound in cultures of 100 mg/dl glucose. The higher concentration of glucose led to significantly less binding (P less than 0.05) (0.24 +/- 0.03% vs. 0.38 +/- 0.02%, n = 6). The addition of mannitol, on the other hand, did not affect binding. All three incubation conditions produced curvilinear competition curves. Scatchard analysis showed that insulin bound significantly less (P less than 0.05) to endothelial cells in 300 mg/dl glucose than to those in 100 mg/dl glucose (4.0 +/- 1.2 nmol/l vs. 12.8 +/- 3.1, n = 6, mean +/- SEM). Insulin binding capacity, however, did not change. We conclude that glucose can reduce insulin binding to endothelial cells and that it may reduce receptor-related insulin transport into and out of the cells.     

Effect of tolbutamide on insulin, glucagon, and somatostatin release from the diabetic rat pancreas with special reference to glucose concentration

The effects of tolbutamide on insulin, glucagon, and somatostatin secretion were investigated in the isolated perfused pancreas from normal and diabetic rats under low (30 mg/dl), normal (100 mg/dl), and high (300 mg/dl) glucose conditions. In the normal rat pancreas, tolbutamide-induced insulin release was increased when the glucose concentration in the perfusion medium was increased from 30-300 mg/dl. Tolbutamide had an inhibitory effect on glucagon release at the low (30 mg/dl) glucose concentrations, although a stimulatory effect was observed under normoglycemic conditions. The total amount of somatostatin secretion above baseline during tolbutamide infusion was higher under the normal glucose than under the low glucose condition. However, further augmentation of somatostatin release was not found at the high glucose concentration. In the diabetic rat pancreas, insulin release was diminished and tolbutamide-induced somatostatin release was enhanced with increasing glucose concentrations. Glucagon release was stimulated at the normal glucose concentration, but inhibited temporarily at the high glucose concentration. The maximum somatostatin response in the early phase was significantly decreased in the diabetic pancreas under low and normal glycemic conditions, when expressed as an incremental change (percentage) above baseline. From these results, one can conclude: (1) tolbutamide has a stimulatory effect on the pancreatic D cell in both the normal and diabetic pancreas; (2) the early response of somatostatin is decreased in the diabetic pancreas, except under conditions of high glucose concentration; and (3) the pancreatic A cell response to tolbutamide was not uniform and was quite different from the response of the D cell.     

雷帕霉素对高糖诱导肾小球系膜细胞增殖的影响

目的 探讨雷帕霉素对高糖诱导肾小球系膜细胞（GMC）增殖的影响及其可能涉及的途径。方法高糖培养GMC,以不同剂量雷帕霉素干预,MTT及流式细胞仪等方法观察雷帕霉素对细胞增殖和周期的影响,RT-PCR、Western印迹观察细胞Cyclin D1、CyclinE和p27^KIP1的变化。结果高糖刺激下,GMC增殖明显;雷帕霉素能抑制这一作用,且呈剂量依赖性,并下调CyclinD1、CyclinE的基因及蛋白水平,上调p27^KIP1的蛋白表达;与对照组相比,高糖组G0／G1期细胞减少,S期细胞比例增加（P均＜0．05）;雷帕霉素干预后,G0／G1期细胞升高,S期细胞比例减少（P均＜0．05）。结论雷帕霉素可抑制高糖状态下GMC的增殖,且呈剂量依赖性;其可能机制是通过下调CyclinD1、CyclinE及上调p27^KIP1,参与了G1／S期阻滞。     

α-亚麻酸对高糖导致的人脐静脉内皮细胞损伤的影响

目的观察α-亚麻酸（ALA）对高糖导致的人脐静脉内皮细胞（HUVECs）损伤的影响,探讨ALA在糖尿病血管并发症防治中的作用。方法采用体外培养的第24代HUVECs,分为6组,即正常对照组、高糖组（HG组）及HG+ALA（ALA浓度分别为10、50、100和200μmol/L）组。各组细胞于不同培养环境中培养72h后收集标本,用MTT比色法测定细胞活力,通过测定细胞上清液中一氧化氮（NO）和丙二醛（MDA）含量评估内皮功能,末端脱氧核糖核酸酶介导的dUTP末端标记法（TUNEL法）和流式细胞仪法检测细胞凋亡情况。结果较低浓度（10、50、100μmol/L）的ALA组中,细胞存活率和合成NO浓度均显著高于高糖组（P<0.05）,MDA浓度和细胞凋亡率显著低于高糖组（P<0.05）;尤以50μmol/L时为著。当ALA浓度增至200μmol/L时,细胞存活率和合成NO浓度反而低于高糖组,MDA浓度和细胞凋亡率也较高糖组进一步增加。结论ALA对高糖环境下培养的内皮细胞有着双重效应,既有保护作用也有细胞毒效应,与其浓度有关。     

Effect of high concentrations of glucose on differentiation of rat trophoblast cells in vitro

AIMS/HYPOTHESIS: Previous studies have shown that diabetic placentas are characterized by structural and biochemical anomalies, including defects in the differentiation of trophoblasts. In this study, the Rcho-1 cell line was used to investigate the impact of high glucose concentrations on different markers of differentiation of rat trophoblast cells in giant cells (endoreduplication, invasive phenotype and endocrine phenotype). MATERIALS: Rcho-1 cells were incubated for 12 days in medium supplemented with different concentrations of glucose and 10% horse serum to optimize differentiation. The cells were examined for the proportion of nuclei showing signs of apoptosis. The effect of high glucose was investigated on the endoreduplication process, on invasive phenotype (secretion of gelatinase B) and on endocrine phenotype (expression of placental lactogen I (PL-I) and II (PL-II) and progesterone secretion). RESULTS: Apoptosis was not induced by high glucose in Rcho-1. The number of cells was higher in the cultures exposed to high glucose (p<0.05) and their nuclei contained more DNA compared with control cells (p<0.001), while their nuclear size was smaller (p<0.001). Gelatinase B secretion increased during differentiation but no difference was found when gelatinase B secretion from trophoblasts exposed to high glucose was compared with the control cells. Rcho-1 cell cultures showed an increase in PL-I and PL-II mRNA expressions during differentiation and which was not affected by high glucose. Progesterone secretion increased during differentiation in control cultures. However, this increase was abolished when trophoblasts were cultured in high glucose. CONCLUSIONS/INTERPRETATION: Our data suggest that high glucose influences the endoreduplication process and the steroidogenesis during differentiation of rattrophoblasts.     

球型脂联素对高糖环境NIT-1胰岛β细胞功能的影响

用β细胞株NIT-1来研究球型脂联素对高糖损伤β细胞分泌功能及相关基因表达的影响.结果 显爪球型脂联素可恢复部分β细胞功能相关基因的表达,抑制高糖诱导NAD(P)H氧化酶组分p47phox表达增加,但未能改善高糖诱导的胰岛素mRNA水平下降及胰岛素分泌缺陷.     

球型脂联素对高糖环境NIT-1胰岛β细胞功能的影响

用β细胞株NIT-1来研究球型脂联素对高糖损伤β细胞分泌功能及相关基因表达的影响.结果 显爪球型脂联素可恢复部分β细胞功能相关基因的表达,抑制高糖诱导NAD(P)H氧化酶组分p47phox表达增加,但未能改善高糖诱导的胰岛素mRNA水平下降及胰岛素分泌缺陷.