[Effect of photoperiod and temperature on fertility alteration of short photoperiod-low temperature induced male sterile rice]

Short photoperiod-low temperature induced male sterile rice is a new germplasm, whose fertility alteration characteristic is contrary to that of long photoperiod and high temperature induced male sterile rice. Compared with that of Yid1s sowed under natural conditions by stages, the fertility alteration of Yid1s was observed under simulated short photoperiod treatment. The results showed that the photoperiod-sensitive stage of Yid1s occurred from differentiation of rachis primordia (phase I) to secondary rachis-branch and spikelet primordia (phase III). The panicles induced by appropriate short daylight treatment at photoperiod-sensitive stage tended to be completely sterile under normal temperature, but the sterile effect was weakened under high temperature. The pollen fertility of Yid1s was reduced under high or low temperature. The temperature-sensitive stages of Yid1s based on the analysis of the effects of high and low temperature on fertility were basically identical, i.e., from pollen mother cell formation (phase V) to single nucleus (phase VII).

Lead-induced hypertension. III. Increased hydroxyl radical production

Lead-induced hypertension has previously been shown to be closely associated with an increase in reactive oxygen species in low lead (100 ppm)-treated rats. The present study has attempted to define the specific moiety involved by noting the blood pressure (BP), reactive oxygen species (MDA-TBA), hydroxyl radical, and nitrotyrosine responses to infusion of the reactive oxygen species scavenger dimethylthiourea. Dimethylthiourea, a reputed scavenger of hydroxyl radical, normalized BP and MDA-TBA in the lead-treated rats but had no effect in normal control animals. MDA-TBA, hydroxyl radical, and nitrotyrosine, the tissue end product of peroxynitrite, were reduced to or toward normal by dimethylthiourea. The results, therefore, are consistent with the suggestion that either hydroxyl radical or peroxynitrite may be the reactive species affected by lead.

[Influence of genetic background of photoperiodic response on expression of short photoperiod sensitive male sterility in rice]

The photoperiodic response of F1 and its parents was analyzed, and the photoperiodic response and short photoperiod sensitive male sterility of F2 progenies were studied in this paper. The results showed that the strong response was dominant over the weak response to photoperiod. The photoperiodic response of plants with short photoperiod sensitive male sterility in F2 was above medial degree(the rate of heading acceleration > 15%). Photoperiodic response showed a positive correlation with short photoperiod sensitive male sterility. The main sterility genes of Yid1s and Yid2s were allelism. It can be inferred that the short photoperiod sensitive male sterile gene might be expressed upon the presence of the photoperiodic response genes, and that the short photoperiod sensitive male sterility of plants with the same genes could differ in their reproductive expressions, not because of the changes of the genes, but the difference in genetic backgrounds of photoperiodic response.

Effect of cyclosporine on HMG-CoA reductase, cholesterol 7alpha-hydroxylase, LDL receptor, HDL receptor, VLDL receptor, and lipoprotein lipase expressions

Long-term administration of cyclosporine (CsA) has been shown to cause hypercholesteremia, hypertriglyceridemia, and elevations of plasma low-density and very low-density lipoprotein (LDL and VLDL) levels in humans. This study was undertaken to explore the effects of CsA on expressions of the key lipid regulatory enzymes and receptors. Thus, hepatic expressions of cholesterol 7alpha-hydroxylase (the rate-limiting step in cholesterol conversion to bile acids), LDL receptor, and high-density lipoprotein (HDL) receptor proteins, as well as 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity were determined in rats treated with CsA (18 mg/kg/day) or placebo for 3 weeks. In addition, skeletal muscle and adipose tissue expressions of lipoprotein lipase and VLDL receptor were measured. Western blot analysis was used for all protein measurements using appropriate antibodies against the respective proteins. CsA-treated animals showed mild but significant elevations of plasma cholesterol and triglyceride concentrations. This was associated with a marked down-regulation of cholesterol 7alpha-hydroxylase in the liver and a severe reduction of lipoprotein lipase abundance in skeletal muscle and adipose tissue. However, hepatic LDL receptor and HDL receptor expressions and HMG-CoA reductase activity were not altered by CsA therapy. Likewise, skeletal muscle and adipose tissue VLDL receptor protein expressions were unaffected by CsA administration under the given condition. In conclusion, CsA administration for 3 weeks resulted in a significant reduction of hepatic cholesterol 7alpha-hydroxylase and marked down-regulation of skeletal muscle and adipose tissue lipoprotein lipase abundance in rats. The former abnormality can contribute to hypercholesterolemia by limiting cholesterol catabolism, whereas the latter may contribute to hypertriglyceridemia and VLDL accumulation by limiting triglyceride-rich lipoprotein clearance in CsA-treated animals.

[The effects of exogenous p16 gene on proliferation and apoptosis of human nasopharyngeal carcinoma cell line CNE-2]

OBJECTIVE

To study the effects of exogenous p16 gene on proliferation and apoptosis of human nasopharyngeal carcinoma cell line CNE-2.

METHODS

Exogenous p16 gene was transfected into CNE-2 cells by lipofectin. After G418 selection, we obtained p16 stably expressed NPC cell clones (CNE-2-p16), and compared it with the mock-transfected clones(CNE-2-vect). Cell cycle was determined by flow cytometry, and cell apoptosis was examined by fluorescent (Hoechst) staining and TUNEL. P16 protein and p53 protein were stained immunohistochemically with relevant antibodies.

RESULTS

Exogenous p16 gene was successfully expressed by CNE-2 2 cells. The growth of CNE-2-p16 cells was inhibited significantly. In CNE-2-p16 cells, cycle arrest in G1 phase, with decrease in percentage of S phase cells. Apoptotic index of CNE-2-p16 was significantly increased. CNE-2-p16 cells were positive for p53 protein that it was negative in CNE-2 cells.

CONCLUSION

Exogenous p16 inhibits proliferation and induces apoptosis of human nasopharyngeal cancer CNE-2 cell line. It may be related to the up-regulation of wild type p53 gene.

[Genetic effect of panicle traits of intersubspecific crosses of rice (Oryza sativa.) and its interaction with environment]

The models of genetic effects and genotype x environment interaction for Additive-Dominant-Additive x Additive epistasis were used to analyze the panicle traits of intersubspecific crosses of rice (Oryza sativa.) in different environments. It was found that significant additive, dominant and additive x additive epistatic effects and genotype x environment (GE) interaction were observed in main panicle length, spikelet density, primary branches, total lengths of primary and secondary branches, but the numbers of main panicle and secondary branches showed no significant additive x environment (AE) interaction and dominant x environment (DE) interaction. The seven traits studied were mainly controlled by dominant effects, but branches traits were more obviously affected by DE interaction. Heritabilities analysis showed that the general heritability in broad sense (HG2) was much larger than other heritabilities. To certain extent, the interaction heritabilities showed their effects in seven panicle traits tested. Heterotic prediction indicated a positive heterosis in all panicle traits except the numbers of primary and secondary branches. GE only influenced the expression extents of heterosis, but was not able to change their directions. According to the predicated genetic effects, IR66158-37, IR65600-85, Minhui63 and R669 were better than other parents in the tactics of breeding for improving panicle traits, because the progenies from these crosses always showed that panicle traits were slightly affected by environment.

[Study on endothlin and its gene expression in splanchnic vessels in cirrhotic rats]

OBJECTIVE

To investigate the role of endothelin(ET) in the pathogenesis of portal hypertension, ET-1 level and its gene expression in splanchnic vessels from cirrhotic rats were observed.

METHODS

ET levels of both plasma and vascular tissues were determined by radioimmunoassay. ET mRNA in vascular tissues was probed with RT-PCR technique expressed as optical density(OD) value from image analysis.

RESULTS

ET peptide and mRNA in PV and SMA vessels were all significantly higher in cirrhotic rats than those in normal rats, while in cirrhotic rats, ET and its gene expression of PV was dramatically higher than that of SMA(P < 0.05). In addition, the positive correlation was observed in difference between PV and SMA in ET concentration with portal pressure(r = 0.737, P < 0.01).

CONCLUSION

ET may be involved in the mechanisms of the formation of portal hypertension mainly due to constructing portal vein, increasing portal flow resistance.

Increased nitric oxide inactivation by reactive oxygen species in lead-induced hypertension

BACKGROUND

We have recently found evidence for increased reactive oxygen species (ROS) in rats with lead-induced hypertension. We hypothesized that increased ROS activity may contribute to hypertension by enhancing inactivation of nitric oxide (NO) in this model.

METHODS

Rats were treated for 12 weeks with either lead acetate (100 p.p.m.) alone (Pb group) or lead acetate plus vitamin E-fortified food (5000 U/kg rat chow, Pb + E group). The control animals were fed either regular rat chow or a vitamin E-fortified diet. Blood pressure, creatinine clearance, and urinary excretion of stable NO metabolites (NOx) were monitored, and plasma and tissue abundance of nitrotyrosine, which is the footprint of NO oxidation by ROS, were determined.

RESULTS

The Pb group showed a marked rise in blood pressure, a significant increase in plasma and kidney, heart, liver, and brain nitrotyrosine abundance, and a substantial fall in urinary NOx excretion. Concomitant administration of high-dose vitamin E in the Pb + E group ameliorated hypertension and normalized both urinary NOx excretion and tissue nitrotyrosine without altering tissue lead content. However, vitamin E supplementation had no discernible effect on either blood pressure or nitrotyrosine abundance in the normal controls.

CONCLUSIONS

These findings point to enhanced ROS-mediated inactivation and sequestration of NO, which can potentially contribute to hypertension, tissue damage, and reduced urinary NOx excretion in rats with lead-induced hypertension. The beneficial effects of high-dose vitamin E on blood pressure, tissue nitrotyrosine burden, and urinary NOx excretion support the role of increased ROS activity in the pathogenesis of these abnormalities in this model.

Down-regulation of hepatic high-density lipoprotein receptor, SR-B1, in nephrotic syndrome

BACKGROUND

Nephrotic syndrome (NS) is a prototype of acquired hypercholesterolemia. Hepatic synthesis and removal of cholesterol play major roles in the regulation of plasma concentration of this sterol. Low-density lipoprotein (LDL) and high-density lipoprotein (HDL) particles are the primary vehicles for cholesterol transport to the liver. We have recently demonstrated that NS results in acquired hepatic LDL receptor deficiency in rats. This study was undertaken to determine the effect of NS on hepatic expression of the newly discovered, long-sought HDL receptor.

METHODS

Hepatic HDL receptor and apolipoprotein A-I (apo A-I) expressions were studied in rats with puromycin-induced NS. The results were compared with those obtained in placebo-treated, normal controls.

RESULTS

The NS group exhibited a marked reduction in hepatic tissue HDL receptor protein abundance when compared with the control group. In contrast, hepatic HDL receptor mRNA abundance in the NS group was similar to that of the control group. As expected, the NS group showed a marked increase in hepatic apo A-I mRNA abundance.

CONCLUSIONS

The study explored the effect of experimental NS on hepatic HDL receptor expression, and the results revealed a marked down-regulation of HDL receptor in rats with NS. In contrast, hepatic expression of Apo A-I, the principal protein constituent of HDL, was markedly increased in NS rats. The HDL receptor deficiency shown here can potentially limit the efficiency of HDL as the primary vehicle for reverse cholesterol transport in NS.

Runners adjust leg stiffness for their first step on a new running surface

Human runners adjust the stiffness of their stance leg to accommodate surface stiffness during steady state running. This adjustment allows runners to maintain similar center of mass movement (e.g., ground contact time and stride frequency) regardless of surface stiffness. When runners encounter abrupt transitions in the running surface, they must either make a rapid adjustment or allow the change in the surface stiffness to disrupt their running mechanics. Our goal was to determine how quickly runners adjust leg stiffness when they encounter an abrupt but expected change in surface stiffness that they have encountered previously. Six human subjects ran at 3 m s(-1) on a rubber track with two types of rubber surfaces: a compliant "soft" surface (ksurf = 21.3 kN m(-1) and a non-compliant "hard" surface (ksurf = 533 kN m(-1). We found that runners completely adjusted leg stiffness for their first step on the new surface after the transition. For example, runners decreased leg stiffness by 29% between the last step on the soft surface and the first step on the hard surface (from 10.7 kN m(-1) to 7.6 kN m(-1), respectively). As a result, the vertical displacement of the center of mass during stance ( approximately 7 cm) did not change at the transition despite a reduction in surface compression from 6 cm to less than 0.25 cm. By rapidly adjusting leg stiffness, each runner made a smooth transition between surfaces so that the path of the center of mass was unaffected by the change in surface stiffness.

Hepatic HDL receptor, SR-B1 and Apo A-I expression in chronic renal failure

BACKGROUND

Chronic renal failure (CRF) is associated with hypertriglyceridaemia and depressed plasma high-density lipoprotein (HDL)-cholesterol and apolipoprotein A-I (Apo A-I) concentrations. Uraemic hypertriglyceridaemia is due, in part, to lipoprotein lipase and hepatic lipase deficiencies, which are causally linked to excess parathormone (PTH). This study was designed to test the hypothesis that depressed plasma concentration and abnormal composition of HDL in CRF may be due to dysregulation of hepatic expression of Apo A-I and/or the newly discovered HDL receptor.

METHODS

Hepatic Apo A-I and HDL receptor mRNA abundance (Northern blot), and HDL receptor protein mass (Western blot) were determined in CRF rats (5/6 nephrectomy), parathyroidectomized CRF rats (CRF-PTx) and sham-operated controls.

RESULTS

The CRF group exhibited normal hepatic HDL receptor mRNA and HDL receptor protein abundance coupled with reduced hepatic Apo A-I mRNA. Hepatic Apo A-I mRNA, HDL receptor mRNA and protein abundance were not affected by PTx.

CONCLUSIONS

CRF results in the down-regulation of hepatic Apo A-I gene expression, which accounts for the known reduction in plasma Apo A-I concentration. However, CRF does not affect HDL receptor mRNA or protein expression in this model. Neither Apo A-I nor HDL receptor expression were modified by PTx in CRF rats.

Effect of increased afterload on cardiac lipoprotein lipase and VLDL receptor expression

Fatty acids are a major source of fuel for energy production by myocytes. Lipoprotein lipase (LPL) and very low density lipoprotein (VLDL) receptor are abundantly expressed by the heart and skeletal muscles. LPL and possibly VLDL receptor represent the primary route of access to fatty acids contained in circulating triglyceride-rich lipoproteins. Physical exercise and thyroid hormone, which promote energy consumption, upregulate LPL expression in skeletal muscles. This study tested the hypothesis that increased cardiac workload might modulate myocardial LPL and/or VLDL receptor expressions. Accordingly, cardiac tissue LPL activity, LPL and VLDL receptor proteins and mRNA abundance were studied in Sprague-Dawley rats 4 weeks after induction of severe thoracic aorta constriction or sham operation. Elevation of afterload with thoracic aortic constriction led to a significant cardiomegaly and a marked upregulation of cardiac LPL activity, LPL mRNA and LPL protein abundance, but did not modify VLDL receptor mRNA or protein abundance. Thus, increased cardiac workload in this model results in upregulation of myocardial LPL expression which can enhance fatty acid availability to accommodate the heart's increased energy requirement.

[Nitric oxide levels in cirrhotic patients]

The aim of this study is to ascertain whether the formation of nitric oxide is argumented in patients with liver cirrhosis and its mechanism. 38 cirrhotic patients and 15 normal controls were studied. Higher plasma levels of NO2-/NO3- (stable end products of nitric oxide), endotoxin, tumor necrosis factor alpha (TNF alpha) and cyclic guanosine monophosphate (cGMP) were observed in patients with cirrhosis than in normal controls (P < 0.01, 0.01, 0.01, 0.05). The higher Child-Pugh, the higher plasma NO2-/NO3- level. The concentration of NO2-/NO3- had a positive correlation with that of endotoxin and TNF alpha (r = 0.481, P < 0.01; r = 0.351, P < 0.05). It is suggested that the production of nitric oxide is augmented and could be induced by endotoxin and TNF alpha. Execessive formation of nitric oxide may be related to hyperdynamic circulation in cirrhosis.

Role of secondary hyperparathyroidism in the genesis of hypertriglyceridemia and VLDL receptor deficiency in chronic renal failure

Recent studies have revealed marked down-regulation of hepatic lipase (HL), lipoprotein lipase (LPL) and very low density lipoprotein-receptor (VLDL-R) expressions in animals with chronic renal failure (CRF). Acquired deficiency of these proteins, which together play an important role in catabolism of triglyceride-rich lipoproteins, is involved in the pathogenesis of CRF hypertriglyceridemia. Down-regulation of HL and LPL expressions in CRF can be completely reversed by parathyroidectomy (PTx), suggesting the role of excess parathormone (PTH). However, the role of hyperparathyroidism in the pathogenesis of CRF-induced VLDL-R deficiency has not been investigated before, and was studied here. To this end, VLDL-R mRNA (Northern analysis) and VLDL-R protein (Western analysis) of the fat pad and soleus muscle were compared in CRF (5/6 nephrectomized) rats, CRF animals with PTx (CRF-PTx) and sham-operated control animals. The CRF animals exhibited marked hypertriglyceridemia coupled with significant reductions in skeletal muscle and adipose tissue VLDL-R mRNA abundance and protein mass. Parathyroidectomy resulted in a significant, but partial, amelioration of CRF hypertriglyceridemia. However, in contrast to its effect on HL and LPL expressions, PTx did not improve VLDL-R expression, suggesting a PTH-independent mechanism for the latter abnormality. The differential effect of PTx on HL and LPL on the one hand and VLDL-R on the other can, in part, account for partial as opposed to complete correction of the associated hypertriglyceridemia with PTx in the CRF animals.

[Radiation-induced apoptosis of two nasopharyngeal carcinoma cell lines]

OBJECTIVE

To study apoptosis induced by radiation in two nasopharyngeal carcinoma (NPC) cell lines, CNE and CNE-2.

METHODS

Hoechst 33342 staining, immunocytochemical staining, RT-PCR, DNA dot blotting and Southern blotting were used to identify apoptosis.

RESULTS

A single dose of X-irradiation resulted in apoptosis, the apoptotic index (AI) was time- and dose-dependent. Different apoptotic responses existed in the two cell lines. Immunocytochemical staining showed that bcl-2 protein was strongly positive in CNE but negetive in CNE-2. However, RT-PCR revealed p53 mRNA in CNE-2 but not in CNE. p53 and bcl-2 genes were both present in the two cell lines as shown by DNA blotting, but the 2.8 kb fragment of the p53 gene was much lower than the 5.6 Kb fragment in CNE which was clearly shown in Southern hybridization, suggestive of partial deletion of p53 gene in CNE.

CONCLUSION

Apoptotic response to radiation is different in 2 NPC cell lines. CNE is more radio-resistant than CNE-2. Overexpression of bcl-2 protein and partial deletion of p53 gene may explain their difference in radio-sensitivity.

Effects of pHGF on hepatocyte DNA synthesis after partial hepatectomy in rats

The effects of pHGF on the changes of hepatocyte proliferative cycle and liver regenerative capacity after partial hepatectomized rats were observed by flow cytometry (FCM). The results were as follows: 1) S phase fraction (SPF) in group of normal rats (group A) accounted for 9.89% and increased gradually within 6 h, following a peak at 12th h or 36th h after operation, but in the group of pHGF-treated rats (group B) the peak appeared at 24th h after operation; 2) Proliferation index (PI) of group A was 19.6% before partial hepatectomy, increased to 34.91% within 6 h and reached a peaks at 12th or 36th h after operation, and in group B the peak appeared at 48th h after operation. There were significant differences between two groups in SPF and PI (P < 0.01). The weight of liver began to increase 12 h after operation, and almost reached the preoperative weight 5 days after operation. These findings suggest that pHGF can promote the DNA synthesis and segmentation of hepatocyte.

Experimental study on the correlation of nitric oxide with portal hypertensive enteropathy

To explore the role of nitric oxide (NO) in the pathogenesis of portal hypertensive enteropathy (PHE), cirrhotic portal hypertension was induced in Wistar rats by subcutaneous administration of carbon tetrachloride. At the end of 12th week, NADPH-diaphorase staining was performed on ice frozen sections with the sample of fresh colonic tissues. NO synthase (NOS) activities and NOS mRNA expression of colonic tissues were investigated with chemoluminescence method and reverse transcription-polymerase chain reaction (RT-PCR), respectively. After NADPH-diaphorase histochemical staining, the computer image analysis and paired t test showed that NOS staining intensities of submucosal vascular endothelial cells and nerve fibers were all significantly higher in PHE group than those in normal group (P < 0.01 and P < 0.05, respectively), but the intensities of superficial epithelial cells were significantly lower than those of controls (P < 0.01). Chemoluminescence method demonstrated that general NOS activity of colonic mucosa was significantly higher in PHE group than that in control group (P < 0.01). Moreover, the degree of iNOS activity increase was greater than that of cNOS (104% vs 35%). RT-PCR revealed that NOS mRNA expressions were dramatically higher in PHE group than those in control group (P < 0.01). The results suggested that NO, with its property of vasodilatation, may be involved in the pathogenesis of vascular lesions of PHE in cirrhotic rats, and may also has something to do with mucosal lesions of colon in PHE.

Secondary hyperparathyroidism downregulates lipoprotein lipase expression in chronic renal failure

In a recent study, we found marked downregulation of lipoprotein lipase (LPL) gene expression in fat, myocardium, and skeletal muscle of rats with chronic renal failure (CRF). Recently, hepatic lipase expression was shown to be depressed in CRF rats, and parathyroidectomy (PTX) was shown to reverse this abnormality. This study was undertaken to determine whether down-regulation of LPL expression in CRF is due to secondary hyperparathyroidism. Accordingly, LPL mRNA (Northern analysis), protein mass (Western analysis using mouse antibovine LPL monoclonal antibody, 5D2), and catalytic activity of the fat pad and soleus muscle were compared in five-sixths-nephrectomized male rats (CRF), parathyroidectomized CRF rats, and sham-operated control animals. The CRF animals exhibited marked hypertriglyceridemia and significant reductions of fat and skeletal muscle LPL mRNA abundance, protein mass, and catalytic activity (P < 0.05 vs. controls, for all parameters). PTX completely normalized the LPL mRNA, protein mass, and enzymatic activity and partially ameliorated the CRF hypertriglyceridemia (P < 0.05 vs. CRF group, for all parameters). Thus secondary hyperparathyroidism is responsible for impaired LPL expression in experimental CRF. This abnormality is completely corrected by PTX.

Gene expression of lipoprotein lipase in experimental nephrosis

Nephrotic syndrome (NS) is commonly associated with marked hypertriglyceridemia, impaired triglyceride-laden lipoprotein clearance, and reduced peripheral tissue uptake of triglycerides from chylomicrons. Lipoprotein lipase (LPL) is the rate-limiting step in triglyceride-rich lipoprotein metabolism. Earlier studies have demonstrated a marked reduction of plasma post-heparin lipolytic activity and LPL protein in NS. However, the effect of NS on gene expression of LPL has not been elucidated. We studied rats with puromycin aminonucleoside-induced NS and the placebo-injected control animals. Heart, soleus muscle, and fat body LPL activity, protein mass, and mRNA were measured and plasma lipid levels were quantitated. The NS group exhibited marked proteinuria, hypoalbuminemia, and hypertriglyceridemia. This was associated with significant reductions of LPL activity and immunodetectable protein in the heart, adipose tissue, and soleus muscle in the NS group. The reduction in LPL protein mass in the tissues tested was accompanied by a parallel reduction in LPL mRNA of the heart but not of either adipose tissue or skeletal muscle, suggesting translational or posttranslational modifications. A negative correlation was found between plasma triglyceride concentration and the LPL, activities of the tissues tested in the study population. Thus this study has revealed a significant down-regulation of tissue LPL protein in experimental NS. This phenomenon can, in part, account for hypertriglyceridemia, impaired catabolism of chylomicrons, and very low-density lipoprotein by peripheral tissues and decreased postheparin lipolytic activity in NS.

Gene expression of LDL receptor, HMG-CoA reductase, and cholesterol-7 alpha-hydroxylase in chronic renal failure

BACKGROUND

Chronic renal failure (CRF) is associated with an atherogenic lipid profile and an increased risk of ischaemic cardiovascular disease. The associated hyperlipidaemia is reportedly ameliorated by erythropoietin (Epo) therapy. According to a recent report, rats studied 3 weeks after 5/6 nephrectomy and fed a high-protein diet exhibited increased activities of hepatic HMG-CoA reductase (HMG-CoAR) and cholesterol 7 alpha-hydroxylase (Ch-7 alpha-H), despite normal corresponding mRNA values.

DESIGN AND METHODS

This study was designed to examine the effects of naturally progressing CRF of longer duration as well as those of Epo therapy on gene expressions of the key factors involved in hepatic cholesterol metabolism, i.e., LDL receptor (LDLR), HMG-CoAR, and Ch-7 alpha-H. Sprague-Dawley rats were randomized to the CRF group (5/6 nephrectomy), Epo-treated CRF group (given Epo 150 U/kg/twice weekly) and sham-operated, placebo-treated normal controls. They were allowed free access to regular rat chow and studied 6 weeks after surgery. Liver mRNAs and protein mass or activities of the above factors were studied.

RESULTS

Plasma cholesterol concentration was significantly increased in the CRF group (P < 0.001) and was modestly lowered (P < 0.05) by Epo therapy. However, microsomal cholesterol concentration and LDLR, HMG-CoAR, and Ch-7 alpha-H mRNA as well as HMG-CoAR activity, and Ch-7 alpha-H and LDLR protein mass measurements were virtually identical in the three groups. Thus, hepatic LDLR, HMG-CoAR, and Ch-7 alpha-H mRNA and protein measurements in rats with CRF were similar to those of the normal control group representing an inappropriate response to the associated hypercholesterolemia. Epo therapy led to partial amelioration of CRF-associated hypercholesterolaemia with no discernible effect on hepatic tissue expression of the above factors.

Acquired VLDL receptor deficiency in experimental nephrosis

Nephrotic syndrome (NS) is commonly associated with elevation of plasma very low density lipoprotein (VLDL) and triglyceride concentrations. VLDL receptor (VLDL-R) is a novel protein that specifically binds and internalizes VLDL particles and is primarily distributed in heart, skeletal muscle, brain and adipose tissue. Based on these properties, VLDL-R is thought to play a role in VLDL and triglyceride metabolism. The present study was undertaken to test the hypothesis that elevation of plasma VLDL in NS may be, in part, related to VLDL-R deficiency. To this end, heart and skeletal muscle VLDL-R protein (Western blot) and mRNA (Northern blot) were measured at various points in the course of puromycin-induced NS in rats. The results were compared with those obtained in the placebo-treated normal control animals. The NS group showed a significant decline in VLDL-R protein (relative to total plasma membrane protein mass) in the heart and skeletal muscle paralleling the rise in plasma VLDL and triglyceride concentrations. The fall in VLDL-R protein was accompanied by a parallel decline in VLDL-R mRNA in the heart but not skeletal muscle. VLDL-R protein was directly related to proteinuria and inversely related to plasma VLDL and triglyceride concentrations. In conclusion, puromycin-induced NS in rats is associated with profound reduction in heart and skeletal muscle VLDL receptor protein. Acquired VLDL-R deficiency, shown for the first time here, may contribute to elevation of plasma concentration of triglyceride-rich VLDL in the nephrotic rat. Recognition of this abnormality reveals another dimension of the complex dysregulation of lipid metabolism in NS. The precise mechanism responsible for NS-induced VLDL-R deficiency in this model is not clear and awaits further investigation.

Down-regulation of hepatic lipase expression in experimental nephrotic syndrome

Hepatic lipase (HL) plays an important role in catabolism of chylomicron remnants, conversion of intermediate density lipoprotein (IDL) to low-density lipoprotein (LDL) and reverse transport of cholesterol to the liver. Several features of the nephrotic dyslipidemia point to the possible presence of HL deficiency. In an attempt to address this possibility, gene expression of HL was studied in rats with puromycin-induced nephrotic syndrome (NS). The results were compared with those obtained in a group of placebo-treated control animals. The NS group showed marked proteinuria, hypoalbuminemia, hypercholesterolemia, hypertriglyceridemia, normal creatinine clearance and normal hepatic tissue cholesterol concentration. HL activity of the liver tissue was reduced by approximately 60% in the NS group as compared to that found in the normal control group. The reduction of HL activity in the NS group was accompanied by a reduction of HL mRNA of virtually similar magnitude. HL activity of the liver tissue was inversely related to urinary protein excretion, serum cholesterol and serum triglyceride concentrations. In contrast, HL activity was directly related to serum albumin concentration and HL mRNA. No significant difference was observed in HL activity between the control group and the pre-nephrotic animals studied at days 1 and 5 following puromycin administration. This observation excludes an acute effect of puromycin as a possible cause of HL deficiency in the NS animals. Thus, NS in this model results in a marked down-regulation of HL expression which may, in part, contribute to the nephrotic dyslipidemia.

Down-regulation of VLDL receptor expression in chronic experimental renal failure

VLDL receptor (VLDL-R) is a novel member of the LDL receptor gene family with distinct tissue distribution and function. It binds and internalizes VLDL particles and is primarily expressed in skeletal muscle, heart, brain and adipose tissue, which use fatty acids for energy production or storage. CRF is associated with elevated serum triglyceride and VLDL concentrations and depressed VLDL and chylomicron clearance. We have recently shown marked down-regulation of lipoprotein lipase expression in CRF. This study was conducted to test the hypothesis that VLDL-R expression may be similarly depressed in CRF. To this end, VLDL-R mRNA (Northern blot) and protein mass (Western blot) of skeletal muscle (soleus) and heart were measured in male Sprague-Dawley rats six weeks after 5/6 nephrectomy (CRF group) or sham operation (NL group). A group of erythropoietin (EPO)-treated (150 U/kg twice weekly) CRF animals was included to determine the possible effect of EPO-deficiency anemia (EPO-CRF group). Subgroups of animals were studied at weeks 1, 3 and 6. The CRF group showed a fivefold increase in plasma triglyceride concentration. This was associated with an impressive fourfold reduction in heart and skeletal muscle VLDL-R mRNA and protein mass. VLDL-R mRNA levels in the heart and skeletal muscle were directly related to creatinine clearance and inversely related to serum triglyceride and VLDL concentrations. EPO therapy led to a mild improvement in CRF hypertriglyceridemia but failed to improve VLDL-R expression. Thus, the rise in plasma triglyceride and VLDL concentrations in CRF animals was associated with marked down-regulation of VLDL-R expression. Down-regulation of VLDL-R expression, shown here for the first time, reveals another facet of disturbed lipid metabolism in CRF.

Nitric oxide synthase activity in arterial tissues of cirrhotic rats

The changes in the activities of constitutive nitric oxide (NO) synthase (cNOS) and inducible NOS (iNOS) were investigated in arterial tissues of CCl4-induced cirrhotic adult SD rats. The aortic tissue homogenate were prepared in normal and cirrhotic rats. NOS activity was measured by conversion of 3H-arginine to 3 H-citrulline. The activities of cNOS and iNOS were calculated in terms of presence or absence of Ca2+. The results showed that activities of total NOS, cNOS and iNOS in arterial tissues were all increased significantly in cirrhotic rats as compared with those in normal controls. There was a significant positive correlation between the activities of total NOS and cGMP content in cirrhotic arterial tissues.