Nobuyoshi Takagi

Tissue-Specific Regulation of Angiotensinogen Gene Expression in Spontaneously Hypertensive Rats

Angiotensinogen is expressed in many tissues besides the liver. Recent studies have suggested that abnormalities in the regulation of angiotensinogen gene expression may be involved in the development of hypertension. However, little information is available concerning the functional significance of tissue angiotensinogen. In this study, we measured plasma angiotensinogen concentration by radioimmunoassay and examined the expression of tissue angiotensinogen by Northern blot analysis in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Although plasma angiotensinogen concentration in SHR was comparable to that in WKY at 6 weeks of age, it was increased significantly at 14 weeks of age in SHR and became higher than that in WKY. The levels of hepatic angiotensinogen mRNA were similar in SHR and WKY, and the levels of aortic, adrenal, and renal angiotensinogen mRNAs were lower in SHR than in WKY at both 6 and 14 weeks of age. Brain angiotensinogen expression in SHR was higher than in WKY at 6 weeks of age and was comparable to that in WKY at 14 weeks of age. On the other hand, cardiac and fat angiotensinogen mRNA levels were significantly increased at 14 weeks of age in SHR. These results demonstrate that the expression of tissue angiotensinogen is regulated differently in SHR and WKY and indicate that the development of hypertension is accompanied at least temporally with increases in plasma angiotensinogen concentration as well as cardiac and adipogenic angiotensinogen mRNA in SHR.

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.

Antihypertensive effects and pharmacokinetics of single and consecutive doses of cilazapril in hypertensive patients with normal and impaired renal function.

The antihypertensive effects and pharmacokinetic properties of cilazapril, a long-acting angiotensin-converting enzyme (ACE) inhibitor, were investigated in hypertensive patients with normal renal function (NRF; n = 5) and those with impaired renal function (IRF; n = 7). A 1.25-mg dose of cilazapril was administered orally once a day for 5 or 8 days. Measurement of blood pressure and sampling of blood specimens were done on the first and last days of treatment. Cilazapril induced significant falls in systolic and diastolic blood pressures as early as 1 h after administration. The antihypertensive effects were still present at 24 h postdose. Serum ACE activity was markedly suppressed over 24 h, with the enzyme inhibition greater in the IRF group. Plasma levels of the active diacid in the IRF group were higher than those in the NRF group, with significant differences in the peak levels and areas under the curve (AUC). A significant inverse correlation was found between the creatinine clearance and the AUC for the diacid. Cilazapril was well tolerated by all the patients, and no adverse reactions were observed. These results suggest that cilazapril has a long-lasting action and that it is a useful antihypertensive agent for controlling blood pressure in patients with either NRF or IRF.

Slow Hemodialysis Performed during the Day in Managing Renal Failure in Critically III Patients

Slow hemodialysis (HD) was performed for 10 h during the day in 11 critically ill patients with renal failure. The dialysis method was a modification of the pump-driven continuous venovenous HD. A nonsterile bicarbonate-containing hemodialysate was passed into the EVAL membrane dialyzer at a flow rate of 30 ml/min. No patient developed further hemodynamic instability during the treatment. The serum urea level was maintained below 20 mmol/l within 4 days of initiating the treatment. It allowed the patients to rest without interruption at night. This method was safely conducted by general nursing staff under the supervision of nephrologists on duty during the day. This schedule offers an approach to renal replacement therapy for hemodynamically unstable patients without any potential problem in the extracorporeal circulation at night.

Molecular mechanism of adipogenic activation of the angiotensinogen gene.

Angiotensinogen gene expression is controlled in a tissue- and development-specific manner. Interestingly, the angiotensinogen gene is abundantly expressed in adipose tissues other than the liver, where it is mainly produced. We investigated the molecular mechanism of angiotensinogen gene expression in a 3T3-L1 preadipocyte-adipocyte system. Although angiotensinogen mRNA was barely detectable in preadipocytes, its levels increased significantly during differentiation. As a whole, the pattern of the change in transcriptional activity of the angiotensinogen promoter was similar to that of the angiotensinogen mRNA levels during adipogenic differentiation, indicating that the activation of the angiotensinogen promoter might be involved in the adipogenic differentiation-coupled gene expression. The proximal promoter region, from -96 to +22 of the transcriptional start site, was sufficient to confer adipogenic activation, and the proximal element from -96 to -52 of the transcriptional start site was necessary for this promoter stimulation. DNA-protein binding experiments showed that this proximal element specifically bound to a nuclear factor induced by adipogenic differentiation. These results suggest that the proximal promoter element from -96 to -52 plays a role in adipogenic activation of the angiotensinogen promoter.

Antihypertensive effects and pharmacokinetics of single and consecutive administration of doxazosin in patients with mild to moderate essential hypertension.

A single dose of doxazosin, a long-acting postsynaptic α1-adrenoceptor antagonist, was administered to seven patients with essential hypertension. Following administration of a single dose, all the patients except one who was forced to be discharged from the hospital for work, continuously received doxazosin once daily (o.d.) for evaluation of its consecutive dosing effect. The antihypertensive effect, pharmacokinetics, and effects on the plasma renin activity (PRA) of doxazosin were investigated. Following a 2-mg single dose of doxazosin, the systolic blood pressure (SBP) decreased significantly up to 12 h. whereas consecutive dosing produced a significant decrease in the SBP up to 24 h and a significant decrease in the mean blood pressure up to 24 h as compared with placebo. The pharmacokinetic parameters of doxazosin in both single- and consecutive-dose study were 18.9 and 25.8 ng/ml in Cmax, 11.1 and 12.9 h in half life (t1/2), and 182.0 and 273.0 ng h/ml in area under the curve (AUC)240, respectively. No significant changes were observed in PRA and plasma concentration of catecholamines. Neither were there any observable changes in endogenous creatinine clearance and in the urinary excretion rates of Na, K. and Cl. Doxazosin was well tolerated by all patients, and no untoward effects were observed. Doxazosin effectively reduces blood pressure and, because of its long t1/2 and minimal effects on PRA catecholamines. and electrolytes, seems to be a useful antihypertensive agent in patients with essential hypertension.

Amino acid losses and nitrogen balance during slow diurnal hemodialysis in critically ill patients with renal failure

AbstractObjective: The effects of slow diurnal hemodialysis (slow HD) on amino acid losses and nitrogen balance were studied. Design: Slow HD was conducted for 10 h during the day at the dialysate flow rate of 30 ml/min. The patients received total parenteral nutrition including 40 g of amino acids (6.08 g of nitrogen). The amino acid concentrations in plasma and dialysate were determined and the daily nitrogen balance was calculated from the urea nitrogen appearance. Patients: Six critically ill patients with renal failure were entered into the study. Results: Slow HD eliminated 48.5±4.4 mmol (6.2±0.6 g) of amino acids, representing 16% of the daily amino acid load. The estimated nitrogen balance was –2.3±1.3 g/day. Amino acid nitrogen lost in the dialysate was 1.0±0.1 g, contributing 43% of the daily negative nitrogen balance. Conclusion: The amount of amino acid losses during slow HD should be taken into consideration when designing nutritional schedules for maintaining positive nitrogen balance in critically ill patients.

Pharmacokinetics of single-dose intravenous amikacin in critically ill patients undergoing slow hemodialysis.

ObjectiveThe pharmacokinetics of amikacin were studied in patients undergoing slow hemodialysis (HD).DesignSlow HD was performed at the dialysate flow rate of 30 ml/min. After a single intravenous dose of amikacin 5 mg/kg, pharmacokinetic variables were calculated by fitting indivdual concentration-time curves to a two-compartment open model.Patients6 critically ill patients with renal failure were entered into the study.ResultsThe volume of distribution was 0.35±0.03 l/kg. Total body clearance was 35.1±2.3 ml/min with an elimination half-life of 10.5 h. During a 10.5 h session of slow HD, the serum amikacin concentration decreased from the peak level of 21.3±1.2 mg/l to 7.2±0.9 mg/l.ConclusionSlow HD eliminate amikacin more efficiently than other types of slowly performed renal replacement therapy and had profound effects on the pharmacokinetics. Amikacin elimination by this approach should be taken into consideration for designing a dosage schedule during the treatment.

NEPHROTIC SYNDROME ASSOCIATED WITH MALIGNANT MESOTHELIOMA

Sumi Tanaka, MD, 2nd Department of Internal Medicine, Urafune Hospital, 3-46 Urafune-cho, Minami-ku, Yokohama 232 (Japan) Discharge Admission Total protein ‘Albumin November 1991 Dear Sir, The association between nephrotic syndrome and malignancy has been well documented [1-3]. Several types of glomerular injury have been noted in patients with cancer [2], and the neoplasms that have been implicated include a variety of histological types from different primary sites [3]. We present a case with nephrotic syndrome associated with malignant mesothelioma. A 77-year-old man was admitted to our hospital with systemic edema, generalized weakness, and fatigue. Two years previously he had a pneumonia, at which time urinalysis showed no protein. He had not been receiving any medications. He had been working as an engineer on a ship and had been exposed to asbestos approximately 40 years prior to admission. Physical examination: On auscultation of his lungs, there were decreased breath sounds and some moist rales on the left. Heart sounds and abdomen were normal, and there was no lymphadenopathy. There was pitting edema of the whole body. Laboratory values included the following: total serum protein 5.4 g/dl, serum albumin 1.3 g/dl, total serum bilirubin 0.2 mg/ dl, serum glutamic-oxaloacetic transaminase 32 IU/1, serum glutamic-pyruvic transaminase 22, alkaline phosphatase 556IU/1, blood urea nitrogen 14 mg/dl, serum creatinine 0.8 mg/dl, Na 130 mEq/1, K 3.7 mEq/1, Ca 6.4 mg/dl, P 2.8, serum glucose 141, total cholesterol 184, triglycerides 107 mg/dl, eryth-rocyte sedimentation rate 50 mm/h, hemoglobin 8.9 g/dl, hematocrit 27.4%, white blood cell count 11.1 × lOVμl (with an increase in

Human Atrial Natriuretic Peptide in Aortic and Coronary Sinus Blood During Atrial Pacing in Patients with Ischemic Heart Disease

Summary: This study investigated the plasma concentrations of human atrial natriuretic peptide (hANP) of blood samples obtained from the aorta and coronary sinus (CS) in 19 male patients (mean age of 52.8 ± 2.1 years) with ischemic heart disease before and during atrial pacing. The plasma concentrations of hANP were measured by radioimmunoassay, and the secretion rate of hANP was calculated on the basis of the CS-aorta difference in plasma hANP concentration and the CS flow rate recorded at blood sampling. Before atrial pacing, aortic plasma hANP concentration showed a significant positive correlation with mean pulmonary capillary wedge pressure (r = 0.67, p < 0.002) or mean pulmonary artery pressure (r – 0.71, p < 0.001), and a significant negative correlation with left ventricular ejection fraction (r = −0.50, p < 0.05). During atrial pacing, aortic plasma hANP concentration increased from 67 ± 13 (SEM) to 151 + 33 pg/ml (p < 0.01), CS plasma hANP concentration from 727 ± 121 to 1205 ± 228 pg/ml (p < 0.01), and the hANP secretion rate from 45.4 ± 14.8 to 86.8 ± 28.2 ng/min (p < 0.05, n = 12). The aortic plasma hANP concentration was significantly correlated with the CS plasma hANP concentration (r = 0.81. p < 0.001) or the hANP secretion rate (r = 0.70, p < 0.001). When the patients were divided into the old myocardial infarction group (n = 10) and the angina pectoris group (n = 9), the aortic plasma hANP concentration was significantly higher in the former than in the latter before pacing (p < 0.05). The change in aortic plasma hANP concentration during pacing was significantly smaller in the infarction group than in the angina group (p < 0.05). These results suggest that the secretion rate of hANP determines the circulating level of hANP at rest and during atrial pacing and that the secretion of hANP is influenced by cardiac function.