胰岛素对大鼠骨骼肌细胞脂联素受体基因表达的影响

目的了解体外胰岛素对原代培养大鼠骨骼肌细胞脂联素受体1表达的影响。方法体外原代培养骨骼肌细胞,应用SYBRGreenⅠ染料建立一种快速、可靠的实时定量PCR,对其主要要素进行优化。观察不同胰岛素浓度不同作用时间下,大鼠骨骼肌细胞脂联素受体基因表达水平的动态变化。结果建立敏感、特异、快速检测脂联素受体1mRNA的实时定量PCR方法,随着胰岛素浓度的增加,脂联素受体1表达逐渐降低。在较低浓度（胰岛素浓度〈1nmol/L）时,脂联素受体1表达的降低无统计学意义,当胰岛素浓度增加到10nmol/L及以上时,骨骼肌细胞脂联素受体1表达的降低有统计学意义（P〈0.05）,这种抑制作用1h后出现,24h后达到高峰。结论成功地建立SYBRGreenⅠ实时定量PCR检测脂联素受体基因的表达方法,体外高胰岛素对骨骼肌细胞脂联素受体1mRNA表达有抑制作用,并呈时间和剂量依赖性。     

Regulation of platelet-derived growth factor ligand and receptor gene expression by alpha-thrombin in vascular smooth muscle cells.

Since the expression of genes for platelet-derived growth factor (PDGF)-A and PDGF beta-receptor are reciprocally regulated in vascular wall cells after balloon injury, we have investigated the ability of specific vasoactive molecules or growth factors to reproduce the injury pattern of gene expression in cultured rat smooth muscle cells (SMCs) and assessed the effect of inactivating alpha-thrombin on injury-induced expression of PDGF-A mRNA by vascular wall cells in vivo. The molecules investigated, to which vascular SMCs may be locally exposed after mechanical injury, included vasoactive factors (alpha- and beta-adrenergic agonists, serotonin, histamine, angiotensin II, and endothelin) and growth factors (PDGF-AA, PDGF-BB, basic fibroblast growth factor, insulin-like growth factor, epidermal growth factor, and alpha-thrombin). In cultured rat SMCs, only alpha-thrombin (0.1-100 nM), among these compounds, produced the pattern of transiently increased PDGF-A and decreased PDGF beta-receptor mRNA. PDGF-B chain mRNA levels remained undetectable in these cultured SMCs. The dependence of these changes in gene expression on the proteolytic activity of alpha-thrombin was shown by the interruption of altered gene expression or DNA synthesis after incubating the cultured SMCs with covalently inactivated alpha-thrombin using D-Phe-Pro-Arg chloromethyl ketone, a synthetic direct active-site irreversible inhibitor of alpha-thrombin. Continuous intravenous infusion of this synthetic antithrombin into baboons for 6 hours (100 nmol/kg per minute maintaining constant plasma levels of 3.0 +/- 0.5 microns/ml) after inducing balloon-catheter arterial injury also prevented the threefold increase in expression of PDGF-A mRNA characteristically exhibited by untreated mechanically injured vessels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Myocardial retinoid X receptor, thyroid hormone receptor, and myosin heavy chain gene expression in the rat during adult aging

Although previous studies have shown that cardiac myosin heavy chain (MHC) composition undergoes a switch from the alpha- to beta-isoform in the heart during adult aging, the underlying mechanisms responsible for this switch are unknown. Cardiac MHC gene expression is regulated, in part, by thyroid hormone responsive elements present in the regulatory control regions of the alpha- and beta-MHC genes. Age-associated changes in the expression of thyroid hormone receptors (THRs) and/or retinoid X receptors (RXRs), the heterodimeric partner for THRs, could explain the age-associated changes in MHC expression. Accordingly, we measured mRNA levels for the cardiac muscle MHCs and the rat THR and RXR genes in the left ventricles of Wistar rats at 2, 6, and 24 months of age. Although there were no significant changes in RXR alpha or RXR beta mRNA levels with age, both alpha 1 and alpha 2 THR mRNA levels decreased significantly between 2 and 6 months of age. During this same time period, the mRNA levels for alpha-MHC declined by more than half, whereas beta-MHC mRNA levels remained low and unchanged. On the other hand, between 6 and 24 months, when mRNA levels for beta-MHC increased and alpha-MHC continued to decrease, there was a significant decline in THR beta 1 and RXR gamma mRNA levels accompanied by a reduction in the THR beta 1 and RXR gamma protein levels. These data show a pattern of change that suggests that the decline in alpha-MHC gene expression may be biphasic and due to a decline in alpha 1 (and possibly alpha 2) THR levels between 2 and 6 months of age and a decline in THR beta 1 and RXR gamma levels at later stages. In contrast, the increase in beta-MHC gene expression was associated only with the changes in THR beta 1 and RXR gamma mRNA and protein levels.     

A sauvagine/corticotropin-releasing factor receptor expressed in heart and skeletal muscle.

Corticotropin-releasing factor (CRF) mediates many critical aspects of the physiological response to stress. These effects are elicited by binding to specific high-affinity receptors, which are coupled to guanine nucleotide stimulatory factor (Gs)-response pathways. Recently, a gene encoding a receptor for CRF, expressed in pituitary and the central nervous system (PC-CRF receptor), was isolated and characterized. Here we report the identification and characterization of a second, distinct CRF receptor that is expressed primarily in heart and skeletal muscle and exhibits a specific ligand preference and antagonist sensitivity compared with the PC-CRF receptor. We refer to this second receptor as the heart/muscle (HM)-CRF receptor.