Yohko Nagai

Salt-sensitive hypertension in conscious rats induced by chronic nitric oxide blockade

This study examined the effects of alterations in salt-intake on blood pressure (BP) in rats chronically treated intravenously with or without the nitric oxide synthase (NOS) inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) (8.6 mg/kg/day). The changes in mean arterial pressure (MAP), the renal cortical and medullary blood flow (CBF and MBF), and the sodium balance were determined by implanted optical fibers and laser-Doppler flow measurement techniques in the conscious rats. The results showed that high salt intake (7.4 mEq/day) elevates CBF (139% +/- 15%), but has no significant effect on MAP or MBF in control rats; in L-NAME-treated rats, high salt intake elevates MAP, produces no change in CBF, and decreases MBF (51% +/- 14%), as well as increasing the sodium balance (0.26 +/- 0.23 mEq/day to 1.29 +/- 0.47 mEq/day). The present experiments indicated that NO appears to maintain the MBF during high salt intake and to prevent the changes in MAP, and, in the absence of NO, salt-sensitive hypertension develops. Nitric oxide plays an important role in the development of salt-sensitive hypertension with the change of MBF.

Salivary gland scintigraphy in gastro-esophageal reflux disease

Abstract.Gastro-esophageal reflux disease (GERD) is associated with a decreased salivary flow as well as gastric acid production. This study therefore aimed to investigate functional disorders of salivary glands in patients with GERD.Methods:Thirty-one consecutive patients with GERD underwent salivary gland scintigraphy.Results:If the results defined the optimal cutoff point for determining the decreased salivary secretion as 51 % in parotid glands and 36 % in submandibular glands, a decreased salivary secretion of right parotid gland, left parotid gland, right submandibular gland, and left submandibular gland was found in 39 %, 32 %, 36 %, and 58 %, respectively. Overall, salivary function disorder of at least one major salivary gland was found in 24 patients (78 %) with GERD. There was no difference in the incidence of impaired salivary function between GERD patients with and without erosive esophagitis. Salivary gland function was more frequently diminished than expected in GERD. We concluded that the presence of impaired salivary gland function was considered to be one of risk factors for developing GERD symptoms.

Changes in renal vessels following the long-term administration of an angiotensin II receptor blocker in Zucker fatty rats

Introduction: The nephro-protective effects of angiotensin II receptor blockers (ARBs) are widely known; however, there are few reports of long-term effects focusing on the renal vessels. We studied afferent arteriolar changes induced by the long-term administration of an ARB. Materials and Methods: Thirty-two 6-week-old male Zucker fatty rats (ZFRs) were divided into following four groups (n = 8 in each): ZFR Group and ZFR+High Group fed a standard or high-salt diet, respectively; ZFR+ARB Group and ZFR+High+ARB Group fed a standard or high-salt diet with ARB (Olmesartan, 5 mg/kg/day), respectively. Blood pressure, proteinuria, morphological examinations and glomerular haemodynamics in vivo were studied. Results: Marked proliferative changes in the afferent arteriolar smooth muscle cells (SMCs) were frequently observed in the two groups given ARBs; in the ZFR+ARB group (77.3±10.3%) compared with the two groups without ARB (1.7%, p < 0.005; 1.2%, p < 0.0005) and 37.4±15.6% in the ZFR+High+ARB group. Proteinuria markedly decreased in the groups treated with ARBs, but the glomerular erythrocyte velocities showed no differences. Conclusions: Our findings indicate that long-term ARB administration induced unusual proliferative changes in SMCs of afferent arterioles of ZFRs. These changes could narrow arteriolar lumens and reduce intraglomerular pressure, but they could cause also irreversible damage to the arterioles.

Renal vascular walls in patients with preeclampsia superimposed on essential hypertension

This study was performed to clarify the relationship between changes in contractile proteins in renal vascular walls and the prognosis of hypertension during pregnancy. Twenty preeclamptic patients underwent renal biopsies after delivery and were divided into the following three groups: group I, patients with persistent hypertension after delivery (n = 7; mean age, 34.8 +/- 1.4 years [SE]); group II, patients who became normotensive after delivery and hypertensive again during follow-up (n = 5; mean age, 34.8 +/- 1.6 years), and group III, patients who became normotensive after delivery (n = 8; mean age, 28.0 +/- 1.0 years). We also examined age-matched healthy controls (group IV; n = 7; mean age, 34.9 +/- 1.5 years). Renal biopsy specimens were immunohistochemically stained by the avidin-biotinylated peroxidase complex method using antimonoclonal smooth muscle cell myosin heavy chain isoform antibodies (SM-1, SM-2) and antimonoclonal alpha-smooth muscle cell actin antibody (actin). We estimated and semiquantitatively scored the degree of staining in each section. In interlobular arteries, SM-1, SM-2, and actin staining in group I were significantly reduced compared with group IV (SM-1, SM-2, P: < 0.05; actin, P: < 0.01). In afferent arterioles (Afs), SM-1, SM-2, and actin staining were reduced in group I. SM-2 staining in group I was significantly reduced compared with the other three groups (versus group II, P: < 0.05; versus groups III and IV, P: < 0.01). These findings suggest that phenotypic changes in vascular smooth muscle cells (especially the disappearance of SM-2 in Afs) reflect the stage of underlying essential hypertension and can predict from the change in hypertension during pregnancy whether it will persist after delivery.

Proliferative changes of renal arteriolar walls induced by administration of angiotensin II receptor blocker are frequent in juvenile rats

Introduction: Our previous study of angiotensin II receptor blocker (ARB) administration in rats induced unusual proliferative changes of smooth muscle cells in renal arteriolar walls. The present study examined if the incidence of the changes depended on the rats’ age, and how long it would take to find changes. Materials and methods: Six-week-old (juvenile spontaneous hypertensive rats (SHRs)+ARB group, n=15) and 20-week-old (adult SHRs+ARB group, n=10) male SHRs were fed a standard diet (0.4% NaCl) containing valsartan (10 mg/kg/day; Novartis Co.). Fifteen age-matched SHRs were studied as controls. After 4, 8, and 12 weeks, the rat kidneys were examined under light and electron microscopes and through immunohistochemical studies. Results: Extremely concentric proliferative changes in afferent arteriolar walls were frequently observed in the juvenile SHR+ARB group compared to the adult SHR+ARB group (48.7±6.8% vs 19.3±6.9%; p=0.0307) at the 12th week. Increased renin expression and arteriolar changes were found from the 4th week in the juvenile SHR+ARB group. Conclusion: This study indicates that ARB administration induces unusual proliferative changes and a marked renin-producing cell increase in afferent arterioles more frequently in juveniles than adult rats. It is suggested that the treatment of ARB in juveniles might have a higher risk of changes in renal afferent arterioles.

Association of dominant dystrophic epidermolysis bullosa with end-stage renal failure and hearing loss

Abstract A 9-year-old boy with dominant dystrophic epidermolysis bullosa had hematuria. At the age of 14 he had proteinuria and at the age of 19 he had developed end-stage renal failure. Histopathological diagnosis of glomerular lesions was not made. During the course of his illness, high-frequency sensorineural hearing impairment developed and he became completely deaf. The hearing loss was thought to be caused by fradiomycin ototoxicity, as fradiomycin ointment had been used to treat secondary infections of the skin lesions since he was an infant. To our knowledge, an association of dominant dystrophic epidermolysis bullosa with end-stage renal failure and ototoxicity due to fradiomycin ointment have not been reported previously.

Immunohistochemical study of endothelin-1 in preeclamptic nephropathy

Whether the serum levels of endothelin, a vasoconstrictive peptide produced in the endothelial cell, increase in preeclamptic patients is still controversial. We performed immunohistochemical studies to observe the changes in endothelin-1 (ET-1) in preeclamptic kidney tissues. The monoclonal anti-human ET-1 antibody (Yamasa, Japan) and anti-von Willebrand factor (vWF, Dako, Denmark), a marker of endothelial cells, were used for the studies by the strepto-avidin-biotin peroxidase method (ABC-POD Kit, Wako, Japan). Twenty-nine patients and 12 normal controls were divided into four groups. The preeclamptic group included 14 patients diagnosed with preeclampsia by clinical symptoms of hypertension, proteinuria, and edema occurring in late pregnancy and as having preeclamptic nephropathy. They underwent renal biopsy 16.7 +/- 1.0 (mean +/- SEM) days after delivery. The nephrotic group comprised 10 normotensive nonpregnant patients with nephrotic-range proteinuria examined through biopsy before treatment (six cases of minimal change, two of focal segmental glomerulosclerosis, one of membranous nephropathy, and one of IgA nephropathy). The pregnant women with preexisting glomerular disease group included five pregnant women with normal renal function who were normotensive and had no increase in the amount of proteinuria throughout pregnancy. They underwent renal biopsy 10.8 +/- 2.9 days after delivery (two cases of membranous nephropathy, one of focal segmental glomerulosclerosis, one of thin basement membrane disease, and one of non-IgA mesangioproliferative glomerulonephritis). The normal kidney group comprised 12 healthy tissue samples taken from nephrectomized kidneys (five cases of renal cell carcinoma, one case of lipofibrosarcoma, and six cases of kidney transplant donors). In these four groups, ET-1 and vWF showed equally positive staining in small arteries. VWF also showed positive staining in arterioles and peritubular capillaries in all groups. Although the glomeruli showed positive staining with ET-1 along the capillary walls in the normal group and the nonpregnant nephrotic group, they showed very weak or negative results in the preeclamptic group. Moreover, gravida with underlying glomerular disease without superimposed preeclampsia also showed negative findings of ET-1 in the glomeruli. The glomeruli in the four groups showed positive findings, with vWF readings the same as in the controls. These results indicate that the production of ET-1 in the glomerular endothelial cells decreases in cases of both preeclampsia and normal pregnancy, and the condition may be caused by pregnancy itself.

Direct Renin Inhibitor is Better than Angiotensin II Receptor Blocker for Intrarenal Arterioles.

Background/Aims: We have reported that the long-term administration of angiotensin II receptor blockers (ARBs) induced unusual proliferative changes of renal afferent arteriolar smooth muscle cells (SMCs) in rats, associated with the overproduction of renin. In this study, we examined that a direct renin inhibitor (DRI: Aliskilen; Novartis Pharma Co, USA) might induce different changes on afferent arteriolar walls compared to ARBs. Method: Twenty one 6-weeks-old male spontaneous hypertensive rats (SHRs) were divided into the following three groups: high-dose DRI group (n=7), low-dose DRI group (n=5) and control group (n=9). The rats were fed a standard diet (0.4%NaCl) containing high-dose (150mg/kg/day), low-dose (30mg/kg/day) DRI and without DRI for 12 weeks. The kidneys were examined by histological and immunohistochemical studies. Systolic blood pressure, 24-h urine samples and blood samples were also examined. Results: The afferent arteriolar SMC walls in the two DRI groups showed no proliferative changes. The positive renin expression area was the largest in the high-dose DRI group among the three groups (14.3±4.0µm2, 6.7±2.0µm2, 2.6±0.9µm2/glomerlus, p=0.020, p=0.008, p=0.017, respectively). Conclusion: The long-term DRI administration increases tissue and circulatory renin; however, afferent arteriolar proliferative changes as shown in ARBs were not induced.

Preeclampsia-like glomerular lesions induced by a single injection of lipopolysaccharide (LPS) in pregnant rats

AbstractBackground. We induced pathological changes in the glomerular capillary walls by causing damage to endothelial cells produced by lipopolysaccharide (LPS) injection in pregnant rats and compared the induced lesions with those of human preeclamptic nephropathy, known as glomerular endothelial damage. Methods. Forty-three uninephrectomized and salt-loaded Wistar rats were divided into three groups. Twenty-six pregnant rats (Group I) and 9 nonpregnant rats (Group II) were injected intravenously with LPS (E. coli 055:B5, 130 μg/kg) on day 15 of gestation, and 8 pregnant rats (Group III) were injected with vehicle. The kidneys of the rats were pathologically and physiologically examined on day 20. Glomerular hemodynamic changes were evaluated under a real-time confocal laser-scanning microscope (CLSM) with a high-speed CCD video camera. Results. Twenty-one (81%) rats in Group I showed glomerular microangiopathic lesions detected as endothelial swelling, a double contour of the basement membrane, and intracapillary fibrin deposits by light and electron microscopy. Immunofluorescent analysis showed that fibrinogen deposition colocalized with the endothelial cell markers. The lesions were observed in only one rat (11%) in Group II. The glomerular blood flow decreased significantly in Group I compared with Group III (P < 0.05, 218.7 ± 122.0 vs 883.2 ± 122.0 μm/s). Conclusion. The glomerular lesions induced by injecting LPS in pregnant rats showed endothelial cell abnormalities and secondary intracapillary coagulation. We consider that these glomerular lesions were “specified” during gestation, and they had many histopathological and physiological findings in common with human preeclamptic nephropathy.

Elevation of Blood Pressure During Pregnancy in Uninephrectomized and Salt-Loaded Wistar Rats

Objective: The influence of uninephrectomy and salt loading on blood pressure (BP) during pregnancy was examined in pregnant Wistar rats.Methods: BP was measured by the indirect tail-cuff method every day during pregnancy in the following five groups: group 1 (n = 18, uninephrectomy on the first day of gestation + 8% high-salt diet), group 2 (n = 8, uninephrectomy + 0.4% low-salt diet), group 3 (n = 14, sham operation + high-salt diet), group 4 (n = 8, sham operation + low-salt diet), and group 5 (n = 8, nonpregnant female rats, uninephrectomy + high-salt diet).Results: Systolic BP in Group 1 increased significantly from midpregnancy and exceeded 140 mm Hg in late pregnancy. On day 17 of gestation, systolic BP in Group 1 (140.5 ± 4.3 mm Hg) was significantly higher than in the other four groups (114.8 ± 3.8, 123.1 ± 3.6, 117.9 ± 3.8, 123.0 ± 3.5 mm Hg, P < 0.05, respectively). Systolic BP was increased in uninephrectomized and salt-loaded pregnant rats but not in rats with two kidneys, uninephrectomized r...