Ursodeoxycholic acid protects hepatocytes against oxidative injury via induction of antioxidants

The therapeutic efficacy of ursodeoxycholic acid (UDCA) has been widely demonstrated in various liver diseases, suggesting that UDCA might protect hepatocytes against common mechanisms of liver damage. A candidate for such protection is oxidative injury induced by reactive oxygen species. This study was designed to assess the effects of UDCA on oxidative injury and antioxidative systems in cultured rat hepatocytes. The viability of the hepatocytes dose-dependently decreased after hydrogen peroxide or cadmium administration. Pretreatment with UDCA significantly prevented this decrease in viability. The amounts of glutathione (GSH) and protein thiol increased significantly, but the activities of antioxidative enzymes such as superoxide dismutase, glutathione peroxidase and catalase were unchanged in UDCA-treated hepatocytes. The mRNA levels of gamma-glutamylcysteine synthetase and metallothionein (MT) were significantly higher in UDCA-treated hepatocytes than in controls. In conclusion, UDCA increased hepatocyte levels of GSH and thiol-containing proteins such as MT, thereby protecting hepatocytes against oxidative injury. Our results provide a new perspective on the hepatoprotective effect of UDCA.

Plasma brain natriuretic peptide levels in normotensive noninsulin-dependent diabetic patients with microalbuminuria

Brain natriuretic peptide (BNP), a member of the natriuretic peptide family, is produced and released from cardiac ventricles. BNP regulates the body fluid volume, blood pressure, and vascular tones through the A-type guanylate cyclase-coupled receptor. The presence of renal dysfunction in patients with diabetes affects the plasma levels of atrial natriuretic peptide (ANP). In the present study, we investigated the plasma levels of BNP and ANP and their relationship in normotensive diabetic patients with normoalbuminuria and microalbuminuria. Forty-seven normotensive lean noninsulin-dependent diabetic patients (31 with normoalbuminuria, 16 with microalbuminuria), with normal cardiac function, and 30 age-matched control subjects were enrolled in this study. The plasma levels of BNP in diabetic patients with microalbuminuria were significantly higher than those in diabetic patients with normoalbuminuria (16.7+/-2.4 vs. 9.6+/-1.3 pg/mL, P<0.01) or normal subjects (16.7+/-2.4 vs. 7.0+/-0.6 pg/mL, P<0.01). There was a significant positive correlation between plasma BNP levels and urinary albumin excretion rate in all diabetic patients (r = 0.58, P<0.0001). There was also a significantly positive correlation between plasma BNP and ANP levels in diabetic patients (r = 0.62, P<0.0001). The increased plasma level of BNP in patients with microalbuminuria and its significant correlation with urinary albumin excretion rate suggest that the elevated circulating levels of BNP are caused by the presence of diabetic nephropathy. Down-regulation of A-type guanylate cyclase-coupled receptor of renal tubules may explain the increased plasma levels of both BNP and ANP in normotensive diabetic patients with microalbuminuria.

Significance of exercise QT dispersion in patients with coronary artery disease who do not have exercise-induced ischemic ST-segment changes

The poor sensitivity and the poor predictive value of ST-segment depression have limited the usefulness of the exercise electrocardiogram (ECG) in the diagnosis and evaluation of coronary artery disease (CAD). The QT dispersion (QTD), recorded as the difference between maximal and minimal QT intervals on a 12-lead exercise ECG, is sensitive to myocardial ischemia and may improve the accuracy of exercise testing in patients with CAD who do not show an ST-segment depression. Exercise ECGs were analyzed in 50 subjects who had undergone coronary angiography for clinical indications. None of them showed an ST-segment depression during or after exercise: There were 25 patients with significant coronary artery stenosis and 25 without significant stenosis. The QTD measured before, immediately after, and 1 min after exercise was similar in the 2 groups. The QTD at 3 and 5 min after exercise was significantly greater in patients with CAD than in the controls, and the most marked difference in QTD was observed at 3 min after exercise. A QTD at 3 min after exercise of >60 ms had a sensitivity of 80% and specificity of 88% regarding the diagnosis of CAD. When a deltaQTD (post-exercise QTD minus QTD at rest) at 3 min after exercise of >0 ms was added to a QTD of >60 ms as a condition for positivity, the specificity increased to 96%. QTD measured at 3 min after exercise increases the accuracy of exercise testing in patients with CAD who do not show an ST-segment depression.

Differential involvement of small G proteins in Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by the progressive deterioration of cognitive function and memory in association with the wide-spread presence of senile plaques, neurofibrillary tangles and neuronal cell death. However, its pathophysiology remains unknown. GTP-binding proteins with molecular weights of approximately 20,000 are designated small G proteins. In the present study we quantitatively analyzed the small G proteins, Ras, Rap, Ral and Rab in brains removed at autopsy from controls and AD patients to examine whether small G proteins are equally or differentially affected in AD. Western blot analysis indicated that the protein level of Ras and RalB in both the cytosolic and membranous fractions and that of Rap2 in the cytosolic fraction was significantly decreased, while that of Rab8 in the membranous fraction was significantly increased in AD brains compared with controls. The protein level of other small G proteins was not different between control and AD brains. These results suggest a differential involvement of small G proteins in AD.

Tissue-specific changes of type 1 angiotensin II receptor and angiotensin-converting enzyme mRNA in angiotensinogen gene-knockout mice

This study examined whether type 1 angiotensin II receptor (AT1) and angiotensin-converting enzyme (ACE) mRNAs are regulated during dietary salt loading in angiotensinogen gene-knockout (Atg-/-) mice which are genetically deficient in endogenous production of angiotensin II. Wild-type (Atg+/+) and Atg-/- mice were fed a normal-salt (0.3% NaCl) or a high-salt (4% NaCl) diet for 2 weeks. The mRNA levels were measured by Northern blot analysis. In Atg+/+ mice, concentrations of plasma angiotensin peptides were decreased by salt loading, whereas the treatment increased the brainstem, cardiac, pulmonary, renal cortex, gastric and intestinal AT1 mRNA levels. Salt loading also enhanced renal cortex ACE mRNA levels in Atg+/+ mice. Although plasma angiotensin peptides and urinary aldosterone excretion were not detected in Atg-/- mice, salt loading increased blood pressure in Atg-/- mice. In Atg-/- mice, pulmonary, renal cortex, gastric and intestinal AT1, and renal cortex and intestinal ACE mRNA levels were higher than those in Atg+/+ mice. However, salt loading upregulated AT1 mRNA expression only in the liver of Atg-/- mice, and the treatment did not affect ACE mRNA levels in Atg-/- mice. Furthermore, although the levels of ACE enzymatic activity showed the same trend with the ACE mRNA levels in the lung, renal cortex and intestine of both Atg-/- and Atg+/+ mice, the results of radioligand binding assay showed that cardiac expression of AT1 protein was regulated differently from AT1 mRNA expression both in Atg-/- and Atg+/+ mice. Thus, expression of AT1 and ACE is regulated by salt loading in a tissue-specific manner that appears to be mediated, at least partly, by a mechanism other than changes in the circulating or tissue levels of angiotensin peptides.

Codon 54 polymorphism of the fatty acid binding protein gene and insulin resistance in the Japanese population

AIM

To determine the relationship of the polymorphism at codon 54 of the intestinal fatty acid binding protein gene (FABP2) with insulin resistance and susceptibility to Type 2 diabetes mellitus (DM) in the Japanese population.

METHODS

We evaluated the polymorphism by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 150 Type 2 DM patients and 147 healthy control subjects. The frequency of alleles encoding threonine (Thr54) and alanine (Ala54) at codon 54 of FABP2 in Type 2 DM patients was compared with that of healthy controls. Insulin sensitivity was assessed by the hyperinsulinaemic euglycaemic clamp in Type 2 DM patients with Ala54 homozygotes, Ala54/Thr54 heterozygotes and Thr54 homozygotes and by homeostasis model assessment (HOMA) in the nondiabetic group.

RESULTS

The frequency of alleles encoding Ala54 and Thr54 was 0.59 and 0.41 in Type 2 DM patients, respectively, similar to that observed in nondiabetic controls (0.64 for Ala54 and 0.36 for Thr54). Insulin sensitivity was not significantly different between subjects with and without Thr54 allele either within the DM group or healthy controls.

CONCLUSIONS

The allele encoding threonine in the FABP2 does not predispose to Type 2 DM or insulin resistance in the Japanese population.

Renin-angiotensin system and fibronectin gene expression in Dahl Iwai salt-sensitive and salt-resistant rats

OBJECTIVE

The tissue renin-angiotensin system and extracellular matrix are involved in the cardiovascular hypertrophy and remodeling induced by hypertension. In this study, we examined the gene expression of the tissue renin-angiotensin system and fibronectin in inbred Dahl Iwai salt-sensitive and salt-resistant rats.

MATERIALS AND METHODS

Eight pairs of 6-week-old male Dahl Iwai salt-sensitive and salt-resistant rats were fed either a low- or high-salt diet (0.3% or 8% NaCl, respectively) for 4 weeks. Activities of the circulating renin-angiotensin system were measured by radioimmunoassay and the gene expression of tissue angiotensinogen, the angiotensin II type 1 receptor (AT1) and fibronectin were analyzed by Northern blot analysis.

RESULTS

Salt loading significantly increased blood pressure and produced cardiovascular hypertrophy and nephrosclerosis in the salt-sensitive rats. Activities of the circulating renin-angiotensin system were lower in salt-sensitive rats than in salt-resistant rats fed the low-salt diet, and salt loading lowered these activities in salt-resistant rats but not in salt-sensitive rats. In salt-resistant rats, salt loading increased renal, cardiac and aortic angiotensinogen, AT1 and fibronectin messenger (m)RNA expression except for aortic fibronectin mRNA expression. In contrast, in the salt-sensitive rats, salt loading stimulated the expression of cardiac fibronectin and aortic angiotensinogen, AT1 and fibronectin mRNAs. Furthermore, the cardiac and aortic fibronectin mRNA levels in salt-sensitive rats were higher than those in salt-resistant rats when both strains were fed the high-salt diet.

CONCLUSIONS

These results demonstrate that the expression of tissue angiotensinogen, AT1 and fibronectin mRNAs is regulated differently in Dahl Iwai salt-sensitive and salt-resistant rats, and indicate that salt-mediated hypertension activates the cardiac fibronectin gene independently of the tissue renin-angiotensin system and stimulates the aortic fibronectin gene with activation of the tissue renin-angiotensin system.

Extrahepatic biliary cystadenocarcinoma arising from the left hepatic duct

A 54-year-old man, who had no clinical symptoms, underwent a routine health checkup at our hospital. Abdominal ultrasonography disclosed a well demarcated tumor containing a solid portion occupying the dilated left hepatic duct and a cystic portion expanding into the parenchyma of the left hepatic lobe, with mild dilatation of the intrahepatic bile ducts. These findings were later confirmed by computed tomography (CT) and magnetic resonance imaging. Endoscopic retrograde cholangiography revealed a complete defect at the level of the left hepatic duct, while drip infusion cholangiographic-CT (DIC-CT) disclosed a defect of the left hepatic duct only, with the distal portions of the left intrahepatic ducts being visualized on the image. Hepatic angiography revealed light stains in the solid portion in the parenchymal phase. At left lobectomy, a multiloculated polyp-like tumor was found arising from the left hepatic duct and expanding into the parenchyma of the left hepatic lobe. Microscopically, all the lining cells in the cysts and the tumor cells in the solid portion showed the features of papillary adenocarcinoma. In this patient with extrahepatic biliary cystadenocarcinoma, DIC-CT was useful in identifying the site of origin of the tumor, and hepatic angiography was also useful in differentiating this rare malignant tumor from benign cystadenoma.

Differential expression of rat brain bcl-2 family proteins in development and aging

We have previously examined the involvement of the B cell leukemia-2 gene product (Bcl-2) family proteins (Bcl-2, Bcl-x, Bax, Bak, and Bad) in Alzheimer's disease (AD) and found that Bcl-2, Bcl-x, Bak, and Bad were upregulated. As AD is an aging-associated disease, in the present study we examined the developmental and aging-related changes in Bcl-2 family proteins in the rat brain. Immunoblot analyses of brain extracts from embryonic day 19 (E19) to postnatal 96-week-old rats indicated that the Bcl-2 protein level was highest at E19 and decreased after birth. Bcl-x levels remained high from E19 to 96 weeks. Bax levels were high from E19 to 2 weeks and decreased from 4 weeks onward. Bak levels were highest at E19 and decreased abruptly after birth. Bad levels were high from E19 to 2 weeks and decreased abruptly at 4 weeks. The present results suggest that the expression of each Bcl-2 family protein is differentially regulated during development and aging and that the changes in the senescent brains are different from those observed in AD.

Differential expression of rat brain synaptic proteins in development and aging

We have previously reported the differential involvement of synaptic proteins in Alzheimer's disease (AD). As AD is an aging-associated disease, in the present study we examined the developmental and aging-related changes in synaptic proteins such as synaptophysin, synaptobrevin, synaptotagmin, synaptosomal-associated protein 25 (SNAP-25), syntaxin 1/HPC-1 and drebrin in the rat brain. Immunoblot analyses of brain extracts from embryonic day 19 (E19) to postnatal 96-week-old rats indicated that the protein level of synaptophysin and synaptobrevin increased after birth, being highest at 24 weeks, and then decreased with aging. Synaptotagmin was detected at E19, with levels increasing after birth to 96 weeks. SNAP-25 levels were highest at 4 weeks, and then decreased with aging. Syntaxin 1/HPC-1 levels were high at E19 and 1 week, decreasing rapidly from 2 weeks onwards, and drebrin levels were highest at E19 and 1 week, and decreased during aging. The present results suggest that the expression of each synaptic protein is differentially regulated in development and aging.

Significant decreased insulin secretion in a diabetic patient with clinically probable multiple sclerosis

A 39-year-old man with chief complaints of aphasia, disorientation and acalculia was admitted to our hospital. He was diagnosed as a clinically probable case of multiple sclerosis (MS) and his symptoms improved while on steroid pulse therapy. The patient had been diagnosed as having diabetes mellitus 16 years before the onset of MS and his insulin secretion further decreased with time. Slight insulin resistance was observed during a euglycemic hyperinsulinemic clamp study. These results suggested that this patient developed diabetes mellitus mainly due to the decrease of insulin secretion.

Effect of genetic deficiency of angiotensinogen on the renin-angiotensin system

This study examined expression of renin-angiotensin system (RAS) component mRNAs in angiotensinogen gene knockout (Atg-/-) mice. Wild-type (Atg+/+) and Atg-/- mice were fed a normal-salt (0.3% NaCl) or high-salt (4% NaCl) diet for 2 weeks. Angiotensinogen, renin, angiotensin-converting enzyme (ACE), angiotensin II type la receptor (AT1A), and angiotensin II type 2 receptor (AT2) mRNA levels were measured by Northern blot analysis. In Atg+/+ mice, activities of circulating RAS and renal angiotensinogen mRNA level were decreased by salt loading, whereas levels of renal and cardiac ACE; renal, brain, and cardiac AT1A; and brain and cardiac AT2 mRNA were increased by salt loading. Although activities of circulating RAS were not detected in Atg-/- mice, salt loading increased blood pressure in Atg-/- mice. In Atg-/- mice, renal renin mRNA level was decreased by salt loading; in contrast, salt loading increased renal AT1A and cardiac AT2 mRNA levels in Atg-/- mice, and these activated levels in Atg-/- mice were higher than those in Atg+/+ mice fed the high-salt diet. Thus, expression of each component of the RAS is regulated in a tissue-specific manner that is distinct from other components of systemic and local RAS and that appears to be mediated by a mechanism other than changes in the circulating or tissue levels of angiotensin peptides.

Alteration of myo-inositol monophosphatase in Alzheimer's disease brains

myo-Inositol monophosphatase (E.C.3.1.3.25) catalyzes the hydrolysis of myo-inositol 1-phosphate in the presence of Mg2+ at a physiologic pH to form free myo-inositol, maintaining a supply that represents the precursor for inositol phospholipid second messenger signaling systems. In the present study the activity and protein level of myo-inositol monophosphatase were investigated in samples from normal human and Alzheimer's disease (AD) postmortem brains. The separation profile on Sephadex G-100 gel filtration chromatography revealed one major form of myo-inositol monophosphatase in crude extracts from both normal human and AD brains. In AD brains myo-inositol monophosphatase activity and its protein level were significantly higher than in control brains. The activity of myo-inositol monophosphatase per enzyme molecule was similar in control and AD brains. These results suggest that myo-inositol monophosphatase is upregulated in AD, probably reflecting compensatory mechanisms concerned with phospholipid metabolism.

Endocrinological abnormalities in angiotensinogen-gene knockout mice: studies of hormonal responses to dietary salt loading

OBJECTIVE

Physiological roles of the renin-angiotensin system in maintaining blood pressure and sodium-water balance in angiotensinogen gene-knockout mice were evaluated with special reference to endogenous pressor substances.

METHODS

Angiotensinogen-gene knockout mice and control mice were fed a 0.3 or 4% NaCl diet for 2 weeks. Systolic blood pressure and urinary excretions of electrolytes, creatinine, aldosterone, adrenaline, noradrenaline, dopamine and vasopressin were measured.

RESULTS

About 60% of our angiotensinogen-gene knockout mice did not survive until weaning. These mice presented with hypotension and polyuria. Urinary excretion of aldosterone from such mice was significantly lower (not detected) than that from control mice (2.0+/-0.3 pg/mg creatinine). In contrast, urinary excretion of vasopressin from angiotensinogen-gene knockout mice (0.7+/-0.1 ng/mg creatinine) was greater than that from control mice (0.3+/-0.1 ng/mg creatinine), and those of adrenaline and of noradrenaline were similar for knockout and control mice. After salt loading (a 4% NaCl diet), angiotensinogen-gene knockout mice exhibited a significant increase in systolic blood pressure (from 68.3+/-2.9 to 95.9+/-5.9 mmHg), significant decreases in urinary excretions of adrenaline (from 65+/-8 to 40+/-7 pg/mg creatinine) and noradrenaline (from 467+/-48 to 281+/-41 pg/mg creatinine) and no change in excretion of vasopressin compared with such mice fed a 0.3% NaCl diet

CONCLUSION

The present results with angiotensinogen-gene knockout mice confirm that the renin-angiotensin system plays fundamental roles in maintaining the blood pressure and sodium-water balance. Because the vasopressin and catecholaminergic systems may be altered by lack of angiotensin in angiotensinogen-gene knockout mice, these systems perhaps are not able to restore blood pressure and sodium-water depletion to normal levels in these mice.

Serum levels of tumor necrosis factor-alpha are increased in obese patients with noninsulin-dependent diabetes mellitus

To clarify the significance of the serum levels of tumor necrosis factor-alpha (TNF-alpha) in the mechanism of insulin resistance, we studied 12 obese patients with noninsulin-dependent diabetes mellitus (NIDDM). We evaluated the relationship of TNF-alpha levels with the visceral, subcutaneous, and total fat areas measured by computed tomography (CT), and with insulin resistance evaluated by the glucose infusion rate (GIR) observed during an euglycemic hyperinsulinemic clamp study. Controls consisted of 12 normal subjects and 12 nonobese patients with NIDDM. TNF-alpha levels were measured using a high sensitivity enzyme-linked immunosorbent assay. Following admission, all patients with NIDDM participated in a 4-week program of diet and exercise. After this treatment, we evaluated the relationship of the serum levels of TNF-alpha with the area of body fat, the GIR, and the resultant change in the TNF-alpha level. Serum levels of TNF-alpha in the obese patients with NIDDM significantly exceeded those observed in normal subjects (P < 0.01) or in the nonobese patients with NIDDM (P < 0.01). Serum levels of TNF-alpha in obese NIDDM patients showed a significant positive correlation with the area of visceral fat before (r = 0.662, P < 0.03) and after (r = 0.508, P < 0.05) the treatment; similar correlation was observed in all patients with NIDDM before (r = 0.537, P < 0.02) and after (r = 0.430, P < 0.05) the treatment. Serum levels of TNF-alpha in obese NIDDM patients showed a significant negative correlation with GIR after the treatment (r = -0.595, P < 0.05). Serum levels of TNF-alpha were significantly reduced in the obese patients with NIDDM after the treatment (P < 0.01), while those in the nonobese NIDDM patients were unchanged. These results suggest that serum TNF-alpha levels may play an important role in mechanism of insulin resistance associated with obesity.

Dietary salt loading decreases the expressions of neuronal-type nitric oxide synthase and renin in the juxtaglomerular apparatus of angiotensinogen gene-knockout mice

The present study investigates whether neuronal type nitric oxide synthase (N-NOS) in the macula densa participates in the regulation of renal renin expression during altered dietary salt intake in angiotensinogen gene-knockout (Atg-/-) mice. Wild-type (Atg+/+) and Atg+/+ mice were fed a low-salt (0.04% NaCl), normal-salt (0.3% NaCl), or high-salt (4% NaCl) diet for 2 wk. Histochemical staining for NADPH diaphorase (NADPHd) and renin were analyzed morphometrically. Levels of N-NOS and renin mRNA in renal cortical tissues were determined by reverse transcription-PCR and Northern blot analysis, respectively. In animals fed a normal-salt diet, the renal expressions of N-NOS and renin were markedly increased in Atg-/- mice compared with Atg+/+ mice. When mutant mice were fed a high-salt diet, the signal intensity of the NADPHd reaction and the number of positively stained macula densa cells were significantly decreased. The levels of renal cortical N-NOS mRNA were also suppressed by the treatment. These changes were paralleled by decreases in renal renin-immunoreactive areas and the levels of renin mRNA. On the other hand, salt restriction did not produce further significant increases in the renal N-NOS and renin expressions in mutant mice, whereas a parallel inverse relationship was observed between these enzyme expressions and the levels of salt intake in wild-type mice. These results suggest that the N-NOS expression in the macula densa is inversely regulated by salt intake and that the enzyme activity is functionally linked to renal renin production. Salt-modulated renal N-NOS and renin expressions are independent on angiotensin formation in Atg-/- mice.

Angiotensin II receptors in cardiac left ventricles of Dahl rats

1. Dahl Iwai salt-sensitive (DS) rats have been reported as becoming hypertensive with left ventricular hypertrophy (LVH) and heart failure when on a high-salt diet. Their circulating renin-angiotensin system (RAS) has been reported to be suppressed. To evaluate the role of angiotensin II (AngII) type 1 and type 2 receptors (AT1 and AT2, respectively) in LVH, we compared cardiac AT1 and AT2 receptors in 10-week-old DS rats and Dahl Iwai salt-resistant (DR) rats. 2. Seven pairs of 6-week-old male DS and DR rats were fed either a low- or high-salt diet (0.3 or 8% NaCl, respectively) for 4 weeks. Left ventricular AngII receptors were measured by radioligand binding assays using [125I]-[Sar1,Ile8]-AngII in plasma membrane fractions from these four groups. The AT1 and AT2 receptors were distinguished using their specific antagonists CV 11974 and PD 123319, respectively. 3. The high-salt diet increased blood pressure and the left ventricle:bodyweight ratio in DS rats. However, neither Bmax for AT1 and AT2 receptors nor Kd for [125I]-[Sar1,Ile8]-AngII differed between the groups. These results are different from those of other reports of pressure-overload LVH, such as spontaneously hypertensive rats or renovascular hypertension rats, in which AT1 and AT2 receptors were reported to be up-regulated.

Genetic deficiency of angiotensinogen produces an impaired urine concentrating ability in mice

Angiotensinogen gene-knockout (Atg-/-) mice lacking angiotensin II exhibit chronic hypotension. The present study was designed to investigate pathophysiology of Atg-/- mice from the renal functional view. Wild-type (Atg+/+) and Atg-/- mice at 10 weeks of age were housed in metabolic cages for 24-hour urine collection. When provided free access to water, Atg-/- mice showed an increased urine output and a decreased urine osmolality compared with Atg+/+ mice. Urinary excretion and plasma levels of vasopressin were significantly higher in mutant mice than in wild-type mice. On the other hand, urinary excretion of aldosterone in mutant mice was suppressed to the levels under the detection limit of the assay system. The mean plasma aldosterone level of Atg-/- mice was suppressed to 30% of that of Atg+/+ mice. Plasma levels of creatinine, endogenous creatinine clearance, and urinary electrolyte excretion were not different between these mice. In Atg+/+ mice, urine osmolality was markedly increased from 1929 +/- 21 to 3314 +/- 402 mOsm/kg during water deprivation, whereas this parameter in Atg-/- mice did not change significantly (from 1413 +/- 121 to 1590 +/- 92 mOsm/kg). Urinary vasopressin excretion increased during water deprivation from 0.24 +/- 0.04 and 0.70 +/- 0.08 to 0.42 +/- 0.06 and 2.31 +/- 0.35 ng/mg creatinine in wild-type and mutant mice, respectively. Histologic study revealed interstitial inflammation, and atrophic changes in the tubules and papilla in Atg-/- mice. In conclusion, a genetic deficiency of angiotensinogen produced an impaired urine concentrating ability and tubulointerstitial lesions, indicating the critical role of angiotensinogen in developing normal tubular function and construction.

Regulation of cardiac angiotensinogen mRNA in vivo and in vitro

In this study, to investigate the mechanism of hypertension-associated induction of cardiac angiotensinogen in vivo and in vitro, we studied the regulation of angiotensinogen mRNA in the hearts of genetically hypertensive rats and in the rat cardiomyocytes. Levels of cardiac angiotensinogen mRNA were significantly increased in the hypertensive rats. Steady state mRNA levels for angiotensinogen mRNA in cardiomyocytes were increased by angiotensin II and mechanical stretch. The addition of an angiotensin II type 1 receptor antagonist (CV11974) and a transcriptional inhibitor (actinomycin D) completely blocked the induction of angiotensinogen mRNA by angiotensin II in cardiomyocytes. The addition of CV11974 significantly, but not completely, inhibited the induction of angiotensinogen mRNA by mechanical stretch. Actinomycin D completely blocked the induction of angiotensinogen mRNA by stretch in cardiomyocytes. An angiotensin II type 2 receptor antagonist (PD123319) and a protein synthesis inhibitor (cycloheximide) did not affect the induction. These results indicate that the expression of cardiac angiotensinogen mRNA is activated by the development of hypertensive cardiac hypertrophy, and that angiotensin II and mechanical stretch activates the angiotensinogen gene via the angiotensin II type 1 receptor-pathway in cardiomyocytes.

Differential expression of rat brain phospholipase C isozymes in development and aging

Phosphoinositide-specific phospholipase C (PLC) is a key enzyme in signal transduction. In the present study we examined developmental and aging changes in three PLC isozymes (beta 1, gamma 1, and delta 1) in the rat brain. Enzyme assays and immunoblot analyses after gel filtration chromatography of brain extracts from embryonic day 19 and postnatal 4- and 48-week rats indicated that gamma-specific activity was highest in fetal brain and decreased with aging, that beta 1-specific activity was high at 4 weeks but essentially undetected in fetal brain, and that delta 1-specific activity was high at both 4 and 48 weeks with faint detection in fetal brain. Our results suggest that the gamma 1 isozyme may be particularly involved in cell division and growth during the histo-genesis of the central nervous system, while beta 1 and delta 1 isozymes may take part in processes of its maturation and maintenance.

Circulating levels of 7 S domain of type IV collagen and atrial natriuretic peptide in normotensive type 2 diabetic patients with or without retinopathy

Thickening of the basement membrane and other structural alterations of the vascular walls occur frequently in patients with diabetes. The vascular response to atrial natriuretic peptide (ANP) is also altered in these patients. Abnormal vascular response in diabetes may be due to alteration of vascular physicochemical properties induced by accumulation of components of vascular basement membrane. The aim of this study was to evaluate the relationship between circulating levels of the 7 S domain of type IV collagen (7 S-collagen), and ANP in normotensive type 2 diabetic patients with or without retinopathy. Forty-one normotensive type 2 diabetic patients (n = 19 with and n = 22 without retinopathy) and 18 age-matched control subjects participated in the study. Serum 7 S-collagen and plasma ANP levels were measured by radioimmunoassays. Serum 7 S-collagen (4.4 +/- 0.1 vs 3.5 +/- 0.1 ng/ml; p < 0.01) levels and plasma ANP (20.8 +/- 1.0 vs 15.5 +/- 1.0 pg/ml; p < 0.01) were significantly higher in diabetic patients than in normal subjects. Serum 7 S-collagen increased significantly in diabetic patients without retinopathy compared with normal subjects (4.1 +/- 0.1 vs 3.5 +/- 0.1 ng/ml; p < 0.01). Diabetic patients with retinopathy showed significantly higher circulating concentrations of 7 S-collagen (4.6 +/- 0.1 vs 4.1 +/- 0.1 ng/ml; p < 0.01) and ANP (22.9 +/- 1.4 vs 18.9 +/- 1.3 pg/ml; p < 0.05) than those without retinopathy. There was a significant and positive correlation (r = 0.51, p < 0.01) between the circulating levels of 7 S-collagen and ANP in all patients. The results of this investigation showed that increased circulating levels of ANP correlate with the abnormal metabolism of the vascular basement membrane observed in diabetic patients with microangiopathy.