Angiotensin II subtype-1 receptor antagonists improve hemodynamic and renal changes without affecting glucose metabolisms in genetic rat model of non-insulin-dependent diabetes mellitus

The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is a new genetic model of non-insulin-dependent diabetes mellitus (NIDDM). We investigated whether treatment with an angiotensin II (ANGII) subtype-1 receptor antagonist delays the onset of NIDDM and attenuates diabetic nephropathy in the OLETF rat. OLETF rats fed a regular chow were treated with ANGII subtype-1 receptor antagonists (E4177 or TA606) for 22 weeks. Hemodynamic changes, glucose metabolism, and the effects on diabetic nephropathy were examined. Systolic blood pressure increased in OLETF rats in an age-dependent manner. OLETF rats exhibited increases in plasma concentrations of glucose and insulin and developed glucosuria at the age of 28 weeks. The changes in glucose metabolism were associated with proteinuria and an increase in urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG). Morphologic investigation revealed nodular lesions in glomeruli in the OLETF rats. The ANGII receptor antagonist treatment abolished the blood pressure elevation. However, the treatment did not affect plasma glucose and insulin levels and did not significantly reduce glucosuria. Nodular lesions in glomeruli were not improved by the treatment. However, the receptor antagonists significantly reduced proteinuria and urinary NAG excretion. Multivariate analyses revealed that proteinuria was determined by systolic blood pressure, lipid metabolism, and glucose levels in plasma. ANGII subtype-1 antagonism does not improve glucose metabolism in the OLETF rat model of NIDDM, which has abnormalities in the glucose-uptake system. Blood pressure elevation and part of the proteinuria associated with NIDDM depends on the renin-angiotensin system rather than glucose metabolisms per se.

Angiotensin-Converting Enzyme Inhibition Delays Onset of Glucosuria With Regression of Renal Injuries in Genetic Rat Model of Non-Insulin-Dependent Diabetes Mellitus

BACKGROUND: The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is a new genetic model of non-insulin-dependent diabetes mellitus (NIDDM). We investigated whether angiotensin inhibition influences the onset of NIDDM and brings about a regression of renal injury in diabetes mellitus. METHODS AND RESULTS: Six-week-old OLETF rats were treated with the angiotensin-converting enzyme (ACE) inhibitors imidapril or enalapril for 16 weeks. Systolic blood pressure is increased in an age-dependent manner in OLETF rats. In this study, the elevation in systolic blood pressure was dose-dependently reduced by ACE inhibitor treatment. In OLETF rats, plasma concentrations of insulin and glucose increased and the glucosuria occurred at the age of 22 weeks. Simultaneously, OLETF rats exhibited proteinuria and nodular lesions in glomeruli. The ACE inhibitor treatment almost completely reduced glucosuria, and also decreased plasma concentrations of insulin and glucose in OLETF rats. ACE inhibitor treatment lessened the proteinuria and attenuated morphologically the severity of nodular lesions in OLETF rats. Moreover, increases in plasminogen activator inhibitor 1 (PAI-1) in OLETF rats were reduced by the ACE inhibitor treatment, and the improvement of glomerular lesions was related to decreases of PAI-1 and angiotensin II levels in plasma but not to improvement of glucose metabolism. CONCLUSIONS: ACE inhibitors delay onset of NIDDM with attenuation of kidney injury. The regression of kidney lesions is probably due to angiotensin reductions but not to glucose metabolism per se. ACE inhibitor drug therapy may be useful in preventing NIDDM and the subsequent renal injury in patients with NIDDM.

Comparison between cilnidipine and nisoldipine with respect to effects on blood pressure and heart rate in hypertensive patients

Cilnidipine is a new and unique 1,4-dihydropyridine calcium antagonist that has both L-type and N-type voltage-dependent calcium channel blocking actions. We compared the effects of cilnidipine and another once-daily dihydropyridine calcium antagonist, nisoldipine, on 24-h blood pressure and heart rate in patients with essential hypertension. We enrolled 10 hypertensive outpatients [9 men and 1 woman; age, 55+/-3 yr (means+/-SEM)] in this study. Their ambulatory blood pressure and heart rate were monitored for 24 h at intervals of 30 min with a portable recorder (TM-2425) after 8 wk of treatment with cilnidipine (5 to 20 mg once daily) and after 8 wk of treatment with nisoldipine (5 to 20 mg once daily). The order of the two treatments was randomized. Blood pressure and heart rate measurements for a 24-h period were analyzed for four segments of the day: morning (06:00 to 11:30), afternoon (12:00 to 17:30), nighttime (18:00 to 23:30), and sleeping time (0:00 to 5:30). Blood pressure levels were similar during the two treatment periods for each 6-h segment of the day. Heart rate was significantly higher during treatment with nisoldipine than during treatment with cilnidipine in the morning segment [by 4.1+/-1.3 beats/min (p < 0.05)] and the afternoon segment [by 6.4+/-3.6 beats/min (p< 0.05)]. These results suggest that cilnidipine is effective as a once-daily antihypertensive agent and causes reflex tachycardia less than does nisoldipine.

Comparison of 24-hour blood pressure, heart rate, and autonomic nerve activity in hypertensive patients treated with cilnidipine or nifedipine retard

We compared the effects of cilnidipine and nifedipine retard on 24-h blood pressure (BP), heart rate (HR), and autonomic nerve activity in patients with essential hypertension. Cilnidipine is a novel and unique 1,4-dihydropyridine calcium antagonist that has the L-type and N-type voltage-dependent calcium channel-blocking action. Fourteen hypertensive outpatients (four men and 10 women; aged 64 +/- 2 years, mean +/- SEM) were enrolled in this study. Their ambulatory BP and electrocardiogram were monitored for 24 h at intervals of 30 min with a portable recorder after a 4-week drug-free period, after a 4-week treatment period with cilnidipine (5 or 10 mg once daily), and after a 4-week treatment period with nifedipine retard (10 or 20 mg twice daily). The order of the three periods was randomized. Autonomic nerve activity was evaluated by a power spectral analysis of HR variability, by using the high-frequency (HF) component as an index of parasympathetic nerve activity and the ratio of the low-frequency (LF) component to the HF component (LF/HF) as an index of sympathovagal balance. Cilnidipine and nifedipine retard significantly reduced the 24-h BP of these patients to similar extents (cilnidipine, -11 +/- 3/-6 +/- 1 mm Hg; nifedipine retard, -15 +/- 3/-6 +/- 2 mm Hg). Cilnidipine did not change the 24-h average HR, whereas nifedipine retard significantly increased it (+3.3 +/- 1.4 beats/min; p < 0.05). Nifedipine retard significantly increased the LF/HF ratio in the daytime and the nighttime. Such changes were limited to the daytime in the treatment period with cilnidipine. These results suggest that cilnidipine is effective as a once-daily antihypertensive agent and had less influence on autonomic nervous system and HR than did nifedipine retard.

Serum N-acetyl-beta-D-glucosaminidase activity in a genetic rat model of non-insulin-dependent diabetes mellitus

Serum N-acetyl-beta-D-glucosaminidase activity (NAG) is a possible predictor of vascular injury in hypertension. We assessed whether the activity of this enzyme reflects vascular damage in a genetic rat model of non-insulin-dependent diabetes mellitus (NIDDM) in humans. Otsuka Long-Evans Tokushima Fatty (OLETF) rats fed a regular chow were treated with the angiotensin converting enzyme (ACE) inhibitor imidapril for 16 wk. Systolic blood pressure increased in a time-dependent manner in the untreated OLETF rats as compared with that in the control Long-Evans Tokushima (LET) rats. The blood pressure elevation was associated with increases in cardiac and aortic weight. Imidapril treatment significantly attenuated the blood pressure elevation and reduced the increases in cardiac and aortic weight. The untreated OLETF rats had higher plasma glucose and insulin concentrations than did the LET rats and presented with glucosuria at the age of 22 wk. Imidapril treatment strikingly decreased plasma glucose levels and the glucosuria. Plasma insulin concentrations decreased, approaching those of the non-diabetic control LET rats. ACE inhibitor treatment attenuated the nodular lesions in the glomeruli of OLETF rats and improved the kidney function. Serum NAG activity increased significantly by 35% in the untreated rats; this increase was attenuated significantly by imidapril treatment. The reduction in serum NAG activity correlated with improvement in cardiovascular injury. In contrast, there were no changes in urinary NAG excretion in the three OLETF rat groups. In addition, NAG excretion did not correlate with indices of cardiovascular injury. These data suggest that serum NAG activity is useful in predicting injury in the cardiovascular system in rats with diabetes mellitus.

Long-term infusion of kallikrein attenuates renal injury in Dahl salt-sensitive rats

We investigated whether long-term infusion of kallikrein would attenuate renal injury in salt-induced hypertension in Dahl salt-sensitive (Dahl S) rats. A subdepressor dose of purified rat urinary kallikrein (RUK) (700 ng/day) was infused intravenously by an osmotic minipump for 4 weeks in male Dahl S rats fed a high-salt (2% NaCl) diet. This dose did not affect the time-dependent elevation of blood pressure. However, urinary protein excretion was significantly decreased, and the glomerular filtration rate was increased. These beneficial effects were reflected morphologically by an attenuation of the glomerulosclerotic lesions and tubular injury seen in the hypertensive Dahl S rats. The kallikrein infusion increased the urinary excretion of bradykinin and stimulated the excretion of cyclic GMP, suggesting that the kallikrein-kinin-prostaglandin and nitric oxide axes were enhanced by the RUK infusion. The alterations induced by such infusion were potentiated by the concomitant administration of the angiotensin converting enzyme inhibitor alacepril. These studies indicated that long-term replacement with rat tissue kallikrein attenuates renal injury in hypertensive Dahl S rats, and this is probably mediated by an enhanced function of the kallikrein-kinin-prostaglandin and nitric oxide systems.

The implication of renin-angiotensin system on renal injury seen in Dahl salt-sensitive rats

Angiotensin II (Ang II) progresses to remodeling of the cardiovascular system through nonhemodynamic as well as hemodynamic effects. There have been few data in vivo on whether subpressor concentration of Ang II is exerted to injure directly the cardiovascular system in hypertension. To test this hypothesis, we investigated, using Dahl salt-sensitive (Dahl S) rats, whether subpressor dose of Ang II progresses to cardiovascular injury observed in salt-induced hypertension. Recent studies have provided evidence that renin-angiotensin inhibition protects against renovascular injury in human hypertension as well as in experimental animals. Particularly in the case of Dahl salt-sensitive rats, a genetic model of volume-dependent hypertension in humans, they are likely to develop more severe arterial and renal injuries than those seen in spontaneously hypertensive rats with similar blood pressure levels. The mechanism of the susceptibility to hypertensive injuries is uncertain; however, renin-angiotensin inhibition significantly improved morphologic and functional injuries in the kidney of Dahl S rats. Conversely, subpressor dose of Ang II infusion exacerbated renal function and progressed to glomerulosclerotic lesions. Alterations of Ang II concentration in physiologic range influenced morphologic and functional injuries in Dahl S rats. Multivariate analysis revealed that activity of the renin-angiotensin system is an independent risk factor to glomerular injury in salt-induced hypertension. These data are in favor of the therapeutic strategy in human hypertension that inhibition of renin-angiotensin system is of value to produce beneficial effects of blood pressure reduction on organ injuries.

Thromboxane inhibition potentiates antihypertensive effects of alpha 1 adrenoceptor antagonists in the rat

We investigated the influence of the vascular and renal thromboxane system on the antihypertensive effects of the alpha 1 adrenoceptor antagonist (alpha 1 blocker) bunazosin in spontaneously hypertensive rats (SHR). SHR were treated for 2 weeks with the alpha 1, blocker bunazosin (0.5 mg/kg body weight/day). The systolic blood pressure immediately declined with bunazosin treatment, and then rose toward the level observed in untreated SHR. This antihypertensive effect was accompanied by a decrease in the ratio of prostacyclin to thromboxane A2 in the vascular wall and the kidney. A subdepressor dose of the thromboxane synthase inhibitor OKY-046 lessened the thromboxane generation during bunazosin treatment, and synergistically potentiated the antihypertensive action of the alpha 1 blocker. Such synergy was also observed between OKY-046 and prazosin, an alternative alpha 1 blocker, but not with amosulalol, an alpha 1 blocker having no quinazoline moiety. alpha 1 blockers with a quinazoline moiety dose-dependently stimulate thromboxane generation in cultured smooth muscle cells from SHR. These data indicate that alpha 1 blockers enhance thromboxane generation in the arterial wall and kidney, thereby contributing to the lessening of the antihypertensive effects observed during alpha 1 blocker treatment.

Endothelin-mediated effect of erythropoietin on blood pressure and renal hemodynamics in hypertensive rats

Erythropoietin (EPO) has been reported to induce hypertension in hemodialysis patients with family history of hypertension. In this study, to reveal the mechanism of EPO-induced hypertension, we examined the acute effect of EPO on blood pressure (BP) and renal hemodynamics in genetically hypertensive rats, and we also tested the effect of BQ-123, an endothelin ETA-receptor blocker, on EPO-induced changes in hemodynamics. Male spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY), aged 9-12 wk, were anesthetized, and BP was monitored through the carotid artery. Renal plasma flow (RPF) and glomerular filtration rate (GFR) were measured before and after an intravenous injection of EPO (1,000 U/kg body wt). In another group of SHR, BQ-123 was continuously infused (1.2 mg.kg body wt-1.h-1) during the experiments. The acute injections of EPO increased BP significantly in SHR in a dose-dependent manner, whereas WKY did not show a significant increase in BP after EPO injections. The effect of EPO on BP in SHR was blocked by BQ-123. In SHR, an acute injection of EPO decreased RPF significantly (from 1.78 +/- 0.16 to 1.49 +/- 0.18 ml.min-1.100 g body wt-1, P < 0.05) without a change in GFR, whereas WKY did not show significant changes in either RPF or GFR. The effect of EPO on RPF in SHR was completely blocked by BQ-123 (from 1.92 +/- 0.26 to 1.88 +/- 0.28 ml.min-1.100 g wt-1, NS). EPO caused a significant increase in plasma endothelin ET-1 in SHR (from 2.3 +/- 0.6 to 6.3 +/- 1.6 pg/ml, P < 0.05), but not in WKY. In conclusion, acute administration of EPO raised blood pressure and reduced RPF in SHR, and these vasoconstrictive effects of EPO are mediated via ETA receptors by an enhanced ET-1 release.

Successful erythropoietin treatment for severe anemia in nephrotic syndrome without renal dysfunction

A 62-year-old woman presented with nephrotic syndrome and severe anemia although the renal function was not impaired. Renal biopsy revealed the histology of membranoproliferative glomerulonephritis, and the proteinuria was resistant to steroid therapy. Iron deficiency, bleeding and other causes of anemia were ruled out, however, her serum erythropoietin level was inappropriately low. The anemia was rapidly corrected by administration of recombinant human erythropoietin. It is suggested that inappropriately low erythropoietin level, in part at least, accounts for the anemia in nephrotic syndrome. It is proposed that erythropoietin therapy should be taken into consideration for severe anemia in nephrotic syndrome even when the renal function is not impaired.

Hachimi-jio-gan extract protects the kidney from hypertensive injury in Dahl salt-sensitive rat

We investigated whether the Chinese herbal remedy, Hachimi-jio-gan extract, attenuates the renal injury seen in salt-induced hypertension in Dahl salt-sensitive (Dahl S) rats. Administration of this extract for 5 weeks dose-dependently decreased systolic blood pressure in Dahl S rats fed with a high-salt (2% NaCl) diet. This blood pressure reduction was associated with a decrease in cardiac mass and in thickness of the aortic wall. Urinary excretion of prostaglandin E2 was increased and glomerular filtration rate was improved with this treatment. Glomerulosclerosis and arterial injury in the kidney were morphologically improved. These data suggest that Hachimi-jio-gan extract exhibits an antihypertensive effect, which is associated with partial resolution of renal injury in salt-induced hypertension.

Hydrochlorothiazide Increases Efferent Glomerular Arteriolar Resistance in Spontaneously Hypertensive Rats

BACKGROUND: Micropuncture studies were performed to determine the intrarenal hemodynamic effects of two conventional antihypertensive agents, hydrochlorothiazide (HCTZ) and hydralazine (HYDR) alone and in combination. METHODS AND RESULTS: Male spontaneously hypertensive and normotensive Wistar Kyoto rats (19 weeks old) were treated for 3 weeks with vehicle (control), HCTZ (80 mg/kg/d), HYDR (5 mg/kg/d), or combined therapy (HCTZ 30 mg/kg/d and HYDR 2 mg/kg/d). Each treatment significantly reduced arterial pressure while effective renal plasma flow, glomerular filtration rate and single nephron glomerular filtration rate were unaffected by any treatment in either strain. In spontaneously hypertensive rats HCTZ decreased single nephron plasma flow (111 +/- 8 to 84 +/- 4 nL/min; P <.05) but, despite this reduction, glomerular pressure remained unchanged (51.4 +/- 0.7 to 52.1 +/- 0.8 mmHg) attributable to increased efferent glomerular resistance (1.58 +/- 0.14 to 2.11 +/- 0.12 10 U; P <.05). By contrast, HYDR increased single nephron plasma flow (to 147 +/- 8 nL/min; P <.01) and decreased efferent glomerular resistance (to 1.09 +/- 0.09 U; P <.05). Combined treatment produced responses similar to HCTZ when used alone, thereby nullifying the beneficial efferent glomerular resistance effects: single nephron plasma flow +/- fell (to 89 +/- 7 nL/min; P <.05) and efferent glomerular resistance increased (to 2.05 +/- 0.17 U; P <.05). In Wistar Kyoto rats, HCTZ and combined treatment had no effect. HCTZ alone induced glomerular ischemia that was associated with efferent glomerular arteriolar constriction in these spontaneously hypertensive rats. CONCLUSIONS: These findings provide a possible explanation for the lack of improved renal target-organ damage in controlled multicenter trials employing thiazide diuretics.

A new adenosine subtype-1 receptor antagonist, FK-838, attenuates salt-induced hypertension in Dahl salt-sensitive rats

We investigated the effects of the adenosine type-1 receptor antagonist FK-838 on salt-induced hypertension in Dahl-Sea salt-sensitive (Dahl S) rats. Dahl S rats fed a high-salt (4% NaCl) diet for 4 weeks were treated with FK-838 or hydrochlorothiazide for 4 weeks and alterations in kidney function and morphologic changes were assessed. FK-838 attenuated the development of hypertension in Dahl S rats, and caused a decrease in aortic weight in a dose dependent fashion. The adenosine antagonist did not produce any detectable metabolic disturbance. The blood pressure reduction by FK-838 was associated with attenuation of glomerular and arterial injury in the kidney. The renal protective effect of FK-838 treatment was associated with a reduction of plasma renin activity and plasma aldosterone concentration. In contrast, the thiazide diuretic, which produced almost the same blood pressure reduction as FK-838, did not attenuate renal damage. These data indicate that adenosine A1 receptor antagonism reduces salt-induced hypertension and the consequent renal injuries.

Possible linkage between renal injury and cardiac remodeling in Dahl salt-sensitive rats treated with the calcium channel antagonist benidipine

Interest in cardiovascular protection by calcium channel antagonists has grown over the past decade. We investigated the prevention of cardiac remodeling and renal injury by the long-acting calcium channel antagonist benidipine using 12 week-old Dahl salt-sensitive (Dahl S) rats fed a high-salt (4% NaCl) diet. Six-week benidipine treatment (10 mg/kg chow) decreased systolic blood pressure by 22% in Dahl S rats. This blood pressure reduction was associated with decreases in cardiac mass and weight of the aortic wall. Collagen content in the left ventricle tended to decline with benidipine treatment. In addition, glomerular filtration rate increased by 33% and arterial and glomerular lesions improved morphologically with this treatment. Regression of cardiac mass and collagen content in the left ventricle was due mainly to blood pressure reduction; however, collagen content in the low-pressure right ventricle was not only related to systemic blood pressure but to the severity of renal lesions. These data suggest that the calcium channel antagonist benidipine attenuates cardiac and renal injury in hypertensive Dahl S rats, and that part of the cardiac hypertrophy is due to a non-hemodynamic mechanism that might be responsible for, or be a consequence of, the lesions in the kidney.

Glomerular dynamics and morphology of aged spontaneously hypertensive rats. Effects of angiotensin-converting enzyme inhibition

Relationships between glomerular dynamics and renal injury, micropuncture and histological studies were assessed in 73 week-old normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats divided into untreated and angiotension-converting enzyme inhibitor-treated (quinapril; 3 mg/kg/day; for 3 weeks) groups. Urinary protein excretion (UPE) and histologic arteriolar (AIS) and glomerular (GIS) injury scores were determined. Mean arterial pressure (MAP) of untreated SHR was increased compared with WKY (200 +/- 6 vs 119 +/- 4 mm Hg; P < 0.01), effective renal plasma flow (ERPF) was reduced (1.47 +/- 0.21 vs 3.06 +/- 0.26 ml/min/per g; P > 0.01), and filtration fraction (FF) and total renal vascular resistance (RVR) of SHR were increased (P < 0.01). Single-nephron plasma flow (SNPF) of untreated SHR was decreased (174 +/- 17 vs 80 +/- 9 ml/min; P < 0.01), and single-nephron filtration fraction and afferent arteriolar resistance (RA) were increased (19.4 +/- 1.8 vs 30.0 +/- 2.5% and 1.90 +/- 0.25 vs 9.05 +/- 1.35 U, respectively; both P < 0.01). Despite reduced SNPF, glomerular capillary pressure (PG) increased (49.7 +/- 0.7 vs 53.8 +/- 1.3 mm Hg; P < 0.05), the result of efferent arteriolar constriction (1.15 +/- 0.18 vs 2.84 +/- 0.36 U; P < 0.01). Untreated SHR had higher UPE (13.9 +/- 1.5 vs 42.8 +/- 3.2; mg/100 g per day; P < 0.01) and GIS and AIS scores than WKY (4.3 +/- 1.1 vs 64.3 +/- 8.4 and 16.6 +/- 3.1 vs 96.3 +/- 14.4; both P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Subpressor dose of angiotensin II increases susceptibility to the haemodynamic injury of blood pressure in Dahl salt-sensitive rats

OBJECTIVE

To investigate the effects of subpressor doses of angiotensin II (Ang II) on the progression of renal injuries in Dahl salt-sensitive (Dahl-S) rats with hypertension.

METHODS

Rats were fed a high-salt (4% NaCl) diet and given an Ang II infusion (10 or 50 ng/kg per min, subcutaneously) for 4 weeks.

RESULTS

The plasma Ang II concentration achieved in the high-dose Ang II infusion was lower than that in low-salt (0.3% NaCl) normotensive rats. The Ang II infusion did not affect systolic blood pressure, cardiac hypertrophy or weight of thoracic aorta. However, the high-dose Ang II infusion increased proteinuria by 58%, enhanced the urinary N-acetyl-beta-D-glucosaminase index by 77% and reduced the glomerular filtration rate by 37%. The impaired renal function was associated with a progression of glomerulosclerotic lesions. Neither tubular nor arterial lesions were exacerbated. The infusion did not influence prostacyclin production or urinary cyclic GMP excretion.

CONCLUSION

A subpressor dose of Ang II infusion impairs renal function with progression of glomerulosclerosis, and these alterations may be due to increased susceptibility of the glomerulus in Dahl-S rats to Ang II-induced injuries. Such a mechanism might underlie a predisposition to hypertension-induced organ damage seen in Dahl-S rats with salt-induced hypertension.

Intrarenal hemodynamics in low- and high-output cardiac failure in rats

Cardiac failure is multifactorial in causation, and the underlying physiologic mechanisms are variable, yet their renal effects have been considered more homogeneous. To investigate and compare the intrarenal hemodynamic characteristics in two experimental types (low- and high-output) of cardiac failure, renal micropuncture studies were performed in rats after myocardial infarction (MI) and arteriovenous fistula, respectively. Myocardial infarction was produced by ligation of the left main coronary artery and arteriovenous fistula by direct puncture of the aorta and inferior vena cava below the renal arteries. Pressures and interrenal and glomerular dynamics were obtained using classic micropuncture techniques. Both forms of cardiac failure were characterized by elevated left ventricular end-diastolic pressure (LVEDP), reduced mean arterial pressure, and increased cardiac mass. Left ventricular end-diastolic pressure was higher in MI rats, and effective renal plasma flow (ERPF) tended to be reduced in both forms of cardiac failure. There were no apparent differences in effective renal plasma flow between two models. In addition, single-nephron plasma flow and single-nephron glomerular filtration rate were reduced, and single-nephron filtration fraction and glomerular capillary pressure (PG) were increased in both models. These changes were associated with higher afferent and efferent arteriolar resistances and lower ultrafiltration coefficients. Despite these similarities, PG was higher in MI rats, yet LVEDP correlated directly with PG (r = 0.73; P < 0.001) and efferent arteriolar resistances (r = 0.72; P < 0.01). Therefore, although systemic arterial pressure and effective renal plasma flow were similar in both models of cardiac failure, PG was significantly higher in MI rats with higher LVEDP than in arteriovenous fistula rats.(ABSTRACT TRUNCATED AT 250 WORDS)

New dihydropyridine calcium channel antagonist, pranidipine, attenuates hypertensive renal injury in Dahl salt-sensitive rats

Interest in the cardiovascular protective effects of calcium channel antagonists has increased in the past decade. We investigated prevention of vascular wall remodeling by the long-acting calcium channel antagonist pranidipine in 12-week-old Dahl salt-sensitive (SS) rats with high-salt-induced (4% NaCl) hypertension. Six-week pranidipine treatment (60 mg/kg chow) decreased systolic blood pressure (SBP) by 22% in SS rats. This BP reduction was associated with decreases in cardiac mass and weight of the aortic wall. Glomerular filtration rate (GFR) was increased by 33%, but this did not lead to a decrease in urinary protein or NAG excretion. Morphologic investigation demonstrated striking resolution of arterial injury (medial necrosis and/or hyperplasia, inflammatory cell infiltration, and thrombus formation) by 87% after pranidipine treatment. Glomerular sclerosis was also attenuated by 61%, whereas tubular injury was improved by only 28%. These morphologic changes were reflected in the findings that the capacity of kidney homogenate for generating lipid peroxides was significantly decreased and that collagen levels and pattern type became similar to those of normotensive salt-resistant (SR) rats. Pranidipine also attenuated hypertensive vasculopathy in small arteries of the middle cerebral arteries. Thus, the calcium channel antagonist pranidipine can attenuate the vascular injury that occurs in salt-induced hypertension, a promising property that implicates its clinical usage, particularly in essential hypertension with cardiovascular complications.

Vasoconstrictors and renal protection induced by beta 1-selective adrenoceptor antagonist bisoprolol

We investigated the role of the vasoconstrictors endothelin-1 (ET-1) and thromboxane in renal protection by the beta 1-selective adrenoceptor antagonist, bisoprolol, in Dahl salt-sensitive rats (Dahl S) and salt-resistant rats (Dahl R). Six-week bisoprolol treatment (20 mg/kg chow) reduced systolic blood pressure (SBP) by 14% in Dahl S rats fed a high-salt (4% NaCl) diet. This BP reduction was accompanied by a decrease in aortic wall thickness. ET-1 and thromboxane released from renal cortex was significantly decreased by 17 and 30% with bisoprolol, respectively. Other prostaglandin synthesis was unaffected. Renal function such as proteinuria, N-acetyl-beta-D-glucosaminidase (NAG) excretion, and glomerular filtration rate (GFR) was not influenced by bisoprolol. Morphologic investigation showed that bisoprolol significantly improved glomerular sclerosis by 29% and attenuated arterial damage by 71%, although tubular injury was not affected. The more severe the glomerulosclerotic lesions, the greater the generation of thromboxane and ET. The arterial lesions were positively correlated to thromboxane generation. These data indicate that long-term bisoprolol treatment reduces vasoconstrictive ET-1 and thromboxane generation and that these alterations may be partly responsible for the amelioration of glomerular and arterial injury in Dahl S rats.

Effects of ANG-converting enzyme and alpha 1-adrenoceptor inhibition on intrarenal hemodynamics in SHR

To investigate the prolonged effects of angiotensin-converting enzyme (ACE) inhibition and alpha 1-adrenoceptor blockade on intrarenal hemodynamics, whole kidney and renal micropuncture studies were performed in male 21-wk-old Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats treated for 3 wk with quinapril (3 mg/kg), terazosin (1 mg/kg), or in their combination (quinapril 1.5 mg/kg and terazosin 0.5 mg/kg). In WKY, only quinapril significantly reduced mean arterial pressure (MAP) associated with reduced afferent arteriolar resistance; there were no other significant changes. In contrast, all treatments similarly decreased MAP in SHR. Quinapril increased renal plasma flow and decreased filtration fraction. With respect to intrarenal hemodynamics, quinapril increased single-nephron plasma flow and reduced glomerular capillary pressure (from 53.1 to 47.8 mmHg; P < 0.01), associated with reduced afferent (from 4.80 to 3.17 10(10)dyn.s.cm-5; P < 0.01) and efferent (from 1.70 to 1.17 10(10)dyn.s.cm-5; P < 0.01) arteriolar resistances, and increased ultrafiltration coefficient (from 0.037 to 0.052 nl.s-1.mmHg-1; P < 0.05). Terazosin only reduced arteriolar resistance. The combined treatment attenuated either agent's independent effects on glomerular hemodynamics. These data demonstrate that prolonged ACE and adrenergic inhibition therapy alone or in combination produce different effects than when given by vein, suggesting that prolonged renopressor system inhibition may be more effective than adrenergic in SHR.

Antihypertensive effect of interleukin-2 in salt-sensitive Dahl rats

We investigated the effects of interleukin-2, which stimulates the proliferation and maturation of thymus-derived lymphocytes, on hypertension and organ injuries in genetically hypertensive rats. Interleukin-2 (5 x 10(4) U/kg body wt) was subcutaneously injected into Dahl salt-sensitive rats fed a 4% NaCl diet and spontaneously hypertensive rats once a week for 10 weeks. The effects on blood pressure, cardiovascular hypertrophy, and renal function were evaluated. Interleukin-2 treatment lowered blood pressure in Dahl salt-sensitive rats (162 versus 187 mm Hg, P < .005). This antihypertensive effect was associated with an increase in glomerular filtration rate (589 versus 428 mL/d per 100 g body weight, P < .005) and reduction in cardiac weight (268 versus 305 mg/100 g body weight, P < .05). Interleukin-2 also alleviated the marked glomerular sclerosis in Dahl salt-sensitive rats (glomerular injury score, 151 versus 220; P < .001). In contrast, interleukin-2 did not affect the development of hypertension or organ injuries in spontaneously hypertensive rats. Histologically, glomerular and arterial lesions of the kidney were much less marked in spontaneously hypertensive rats than in Dahl salt-sensitive rats. These data indicate that interleukin-2 ameliorates the development of hypertension and cardiac and renal injuries in Dahl salt-sensitive rats.

De novo synthesis of phospholipase A2 and prostacyclin production by proliferating rat smooth muscle cells

We investigated the role of phospholipase A2 (PLA2) in cell cycle-dependent alterations of endogenous prostacyclin (PGI2) synthesis in aortic smooth muscle cells in culture (VSMC) from Wistar Kyoto rats. Randomly cycling VSMC generated more PGI2 than the stationary cells. Cell cycle analysis showed that PGI2 production capacity was increased from the G0/G1 through the early DNA synthetic (S) phases. Enzyme analysis revealed that, although there were different mechanisms underlying this increase in the PGI2 production during the G0/G1, the peak at 4 hours coincided with a sharp increase in PLA2 activity. This increase in PLA2 activity was preceded by an increased expression of functional PLA2 messenger RNA, and protein synthesis inhibition prevented most of the increase in PGI2 production at 4 hours. These data indicate that endogenous PGI2 generation is mainly increased during the G0/G1 period and that this event is secondary to de novo synthesis of PLA2 and probably, at least in part, to cyclooxygenase induction. This mechanism provides a negative feedback regulating VSMC proliferation.

Inhibition of protein synthesis and antiproliferative effect of the angiotensin converting enzyme inhibitor trandolaprilat in rat vascular smooth muscle cells

OBJECTIVE

To investigate the effect of the angiotensin converting enzyme (ACE) inhibitor trandolaprilat on vascular smooth muscle cell growth, and to analyse its mechanism of action.

DESIGN

Aortic vascular smooth muscle cells (VSMC) from Wistar-Kyoto rats were cultured, and cell proliferation was analysed using a cell synchrony technique.

METHODS

Proliferative activity was assessed by [3H]-thymidine uptake and doubling time. Protein synthesis was assessed by [3H]-leucine incorporation. Actin formation was measured using sodium dodecylsulphate-polyacrylamide slab gel electrophoresis and a densitometric assay. The effect of trandolaprilat on translational protein synthesis was also examined using the cell-free protein synthesis system of reticulocyte lysate and messenger RNA from VSMC.

RESULTS

Trandolaprilat decreased [3H]-thymidine uptake and increased the doubling time of randomly cycling VSMC. The cell synchrony study revealed that this antiproliferative effect was due to increased transition time from S to G2-M. Decreased cell cycle progression during G2-M was reflected by inhibition of cellular protein synthesis during this period. Cellular protein in randomly cycling VSMC was also decreased by trandolaprilat. This decreased protein synthesis was probably produced by inhibition of RNA translation.

CONCLUSIONS

The ACE inhibitor trandolaprilat reduces VSMC proliferation by lengthening the G2-M phase of the cell cycle, and produces a decrease in cellular protein content. This effect is probably mediated by inhibition of protein synthesis at the translational level.

Possible radical scavenging properties of cicletanine and renal protection in Dahl salt sensitive rats

Much interest in cicletanine, a novel antihypertensive drug, has grown because it uniquely stimulates prostacyclin (PGI2) production and may, thereby, provide further cardiovascular protection. We postulated that cicletanine may be an antioxidant, and assessed its ability to protect the kidney in Dahl salt-sensitive (Dahl S) rats on a high salt diet. Cicletanine eradicated in vitro a stable radical, DPPH, and decreased the lipid peroxidation both in rat brain homogenate and in a xanthine-xanthine oxidase (X-XOD) superoxide generating system. Furthermore, cicletanine attenuated the inhibition of PGI2 synthase activity by 15HPETE. However, cicletanine did not exhibit superoxide dismutase-like activity in X-XOD system, suggesting that it behaves primarily as a hydroxy radical scavenger. A 6 week cicletanine treatment reduced blood pressure in Dahl S rats fed a high salt diet, and ameliorated functional and morphological injury to the kidney. This attenuation of glomerular sclerosis correlated with the attenuation of lipid peroxidation in the kidney homogenate. These data indicate that cicletanine is an antioxidant that protects the kidney from salt-induced hypertension in Dahl salt-sensitive strain rats.

Genetic predisposition to hypertension facilitates blood pressure elevation in hemodialysis patients treated with erythropoietin

PURPOSE

This study investigated the hypothesis that a genetic predisposition to hypertension is involved in the etiology of the elevation in blood pressure induced by human recombinant erythropoietin (rHuEPO).

PATIENTS AND METHODS

Blood pressure changes after 10 weeks of treatment with rHuEPO were compared between 26 patients with a positive family history of hypertension and 27 with a negative family history.

RESULTS

Mean blood pressure was significantly increased in patients with a positive family history of hypertension (+8.8 mm Hg, p < 0.001). In contrast, the change was not significant in those whose family history was negative (+1.8 mm Hg, not significant). The mean blood pressure of 14 of 26 patients with a positive family history of hypertension increased by more than 10%, whereas such an increase occurred in only 2 of 27 patients with a negative family history (p < 0.001). The two groups were similar in terms of the total dose of rHuEPO given, the degree to which their anemia improved, and their basal blood pressures.

CONCLUSION

It appears that hemodialysis patients with a positive family history of hypertension are susceptible to developing hypertension during treatment with rHuEPO.