Immunohistochemical localization of distinct angiotensin II AT1 receptor isoforms in the kidneys of the Sprague-Dawley rat and the desert rodent Meriones crassus.

Employing a purified lgG fraction of a polyclonal anti-AT1 receptor anti-body, raised against a synthetic octapeptide encompassing residues 14-21 of the first extracellular domain of the AT1 polypeptide, selective AT1 receptor expression was immunohistochemically demonstrable within renal structures in Sprague-Dawley (SD) rats and the desert rodent Meriones crassus. In both animal models, prominent AT1 receptor labelling was evident in renal vascular elements, particularly cortical inter-lobular arteries (IA) as well as vasa recta bundles in the inner stripe of the outer medulla. Less intense labelling was observed among peritubular capillary endothelia within the deep cortex, and at both the outer stripe and the inter-bundle regions of the inner stripe of the outer medulla. The binding of the anti-peptide anti-body was, however, lacking among glomeruli and, except for the intense labelling confined to basement membranes of Bowman's capsule of deep nephrons, was virtually absent in all renal tubular structures of both animal models. Structural assessment of the expressed AT1 receptors by two-dimensional Western blotting revealed that a spectrum of structurally distinct AT1 receptor isoforms is expressed in the renal tissues of both animal models. This spectrum was constituted by isoforms of equal size (70 kDa) but distinct pls in SD rats, and of both different sizes (67-73 kDa) and isoelectric points in M. crassus. In either species, the charge and/or size heterogeneity of AT1 receptor isoforms may be attributed in part to differential post-translational glycosylation mechanisms of the AT1 receptor polypeptide backbone. The potential for the differential glycosylation state of AT1 receptors to alter recognition properties may add another level of complexity to tissue-specific and/or species-specific mechanisms underlying angiotensin II interactions in the kidney.

Mechanism of garlic (Allium sativum) induced reduction of hypertension in 2K-1C rats: a possible mediation of Na/H exchanger isoform-1.

Garlic causes reduction in blood pressure (BP), however the role of Na/H exchanger (NHE) which mediates hypertension and related tissue-damage is poorly understood. In this study the effect of an established dose of raw garlic extract was investigated on the expression of NHE-1 and -3 and sodium pump activity in a 2K-1C model of hypertension in rats. 2K-1C animals showed high BP, increased serum concentration of PGE2 and TxB2, hypertrophy of the unclipped kidneys, but not in the clipped kidneys In addition, NHE-1 and NHE-3 isoforms were increased in both the 2K-1C kidneys, whereas alpha-actin was increased in the clipped but not in unclipped kidneys. Sodium pump activity was decreased in the clipped kidneys, but remained unchanged in the unclipped kidneys. Garlic treatment reduced the induction of NHE-1 only in the unclipped 2K-1C kidneys, whereas garlic treatment increased the sodium pump activity in both the 2K-1C kidneys. These findings demonstrate that the antihypertensive action of garlic is associated with a reversal of NHE-1 induction in the unclipped kidneys. Induction of NHE isoforms together with a reduced sodium pump activity might cause necrosis in the 2K-1C clipped kidneys due to cellular retention of Na+. On the other hand, activation of sodium pump by garlic extract in the kidneys should reduce intracellular Na+ concentration and normalize BP. These findings signify the use of garlic in the treatment of hypertension.

The use of ginger (Zingiber officinale Rosc.) as a potential anti-inflammatory and antithrombotic agent.

The effect of an aqueous extract of ginger (Zingiber officinale) on serum cholesterol and triglyceride levels as well as platelet thromboxane-B(2) and prostaglandin-E(2) production was examined. A raw aqueous extract of ginger was administered daily for a period of 4 weeks, either orally or intraperitoneally (IP) to rats. Fasting blood serum was investigated for thromboxane-B(2), prostaglandin-E(2), cholesterol and triglycerides. A low dose of ginger (50 mg/kg) administered either orally or IP did not produce any significant reduction in the serum thromboxane-B(2) levels when compared to saline-treated animals. However, ginger administered orally caused significant changes in the serum PGE(2) at this dose. High doses of ginger (500 mg/kg) were significantly effective in lowering serum PGE(2) when given either orally or IP. However, TXB(2) levels were significantly lower in rats given 500 mg/kg ginger orally but not IP. A significant reduction in serum cholesterol was observed when a higher dose of ginger (500 mg/kg) was administered. At a low dose of ginger (50 mg/kg), a significant reduction in the serum cholesterol was observed only when ginger was administered IP. No significant changes in serum triglyceride levels were observed upon administration of either the low or high dose of ginger. These results suggest that ginger could be used as an cholesterol-lowering, antithrombotic and anti-inflammatory agent.

Thromboxane-B2, prostaglandin-E2 and hypertension in the rat 2-kidney 1-clip model: a possible mechanism of the garlic induced hypotension.

Serum collected from unilaterally clipped and unclipped rats before and after treatment with water, garlic or cilazapril and subsequent to measuring blood pressure was assayed for thromboxane-B2 and prostaglandin-E2. The unclipped rats' thromboxane-B2 and prostaglandin-E2 levels were about 23 ng/ml and 2 ng/ml, respectively, and blood pressure was 126+/-3 mmHg. These values were not affected by either water or garlic administration. The clipped rats' thromboxane-B2 and prostaglandin-E2 concentrations were close to 34 ng/ml and 4 ng/ml, respectively, and declined only in response to garlic (by 15 ng/ml and 3 ng/ml) and cilazapril (by 12 ng/ml and 1.5 ng/ml). The blood pressure of these rats was 196+/-7 mmHg and again was reduced only by garlic to 169+/-14 mmHg and cilazapril to 137+/-5 mmHg. The no-treatment and water-treatment readings were significantly higher in the clipped rats. The data suggest that prostanoid system activity in the 2-kidney 1-clip rat is enhanced and mostly toward maintaining the hypertension. Furthermore, the blood pressure lowering effects of garlic and cilazapril might have been induced partially by a greater reduction in the synthesis of vasoconstrictor prostanoids.

Different levels of hypertension induce opposite diuretic behaviors from the nonclipped kidney in the rat two-kidney, one-clip model.

This study was carried out on conscious two-kidney, one-clip (2K1C) rats to establish whether different levels of hypertension induced opposite diuretic behaviors from the nonclipped kidney. Mildly hypertensive rats and severely hypertensive rats were produced by, respectively, constricting their right renal arteries with 0.3-mm and 0.15-mm clips. On the 11th day of the study, the systolic blood pressure (SBP) of the 0.3-mm clip rats was 150 +/- 2 mm Hg, the water intake was 24 +/- 1 ml, and the urine output was 7 +/- 1 ml. The SBP of the 0.15-mm clip rats was 231 +/- 10 mm Hg, the water intake was 46 +/- 4 ml, and the urine output was 27 +/- 6 ml. The data from the two groups are significantly different. On the 19th day half of the mildly hypertensive (0.3-mm clip) rats that received cilazapril from day 15 had, with respect to their water-treated counterparts, a SBP of 140 +/- 8 as compared with 159 +/- 7 mm Hg, the water intake was 37 +/- 5 as compared with 26 +/- 4 ml, and the urine output was 18 +/- 4 as compared with 12 +/- 1 ml. In contrast, half of the severely hypertensive (0.15-mm clip) rats that received cilazapril had, with respect to their water-treated counterparts, a SBP of 143 +/- 4 as compared with 227 +/- 10 mm Hg, the water intake was 30 +/- 2 as compared with 51 +/- 9 ml, and the urine output was 8 +/- 2 as compared with 29 +/- 4 ml. All changes induced by cilazapril are significant in both groups. The data of this study suggest that different levels of hypertension in the rat 2K1C model induce opposite water elimination modes from the nonclipped kidney. This conclusion is supported by the different shift in the water intake and urine output among the cilazapril-treated rats of the two groups. This contrast in the response to cilazapril seems to be dependent on the magnitude of the resulting hypotension. Thus, it seems that in this model, when the hypertension is mild, the antidiuretic effect of angiotension II on the nonclipped kidney is exhibited, whereas, when the hypertension is severe, the diuretic influence of the blood pressure is evident. Irrespective of these different characteristics of the submodels of 2K1C, angiotensin I converting enzyme inhibitors, such as cilazapril, are effective in normalizing the blood pressure.

Effect of allicin from garlic powder on serum lipids and blood pressure in rats fed with a high cholesterol diet.

The use of fresh aqueous garlic extract is known to be effective in reducing thromboxane formation by platelets in both in vivo and in vitro animal models of thrombosis. In the present study, we studied the effect of Lichtwer garlic powder (containing 1.3% alliin equivalent to 0.6% allicin) on the serum cholesterol, triglyceride, glucose, protein, and systolic blood pressure in rats fed with a high cholesterol diet. Experimental rats were fed a 2% high cholesterol diet with and without garlic powder for 6 weeks. Control rats were fed a normal diet. The aqueous garlic powder extract was given orally to rats on a daily basis. It was observed that cholesterol-fed animals had a significant increase in serum cholesterol compared to the control group of rats fed on a normal diet. However, when the rats were fed with a high cholesterol diet mixed with garlic powder, there was a significant reduction in their serum cholesterol levels compared with the group which were on a diet containing high cholesterol without garlic powder. Serum triglyceride levels were also significantly lowered by garlic powder when compared to control and high cholesterol diet group rats. The blood pressure of the high cholesterol diet animals was significantly higher compared to the animals receiving the control diet. The blood pressure of the animals receiving garlic powder and high cholesterol diet was significantly lower as compared to the high cholesterol and control diet group. No significant changes were observed in the serum glucose and protein in all of the rats. These results show that garlic is beneficial in reducing blood cholesterol, triglycerides levels and systolic blood pressure in hypercholesterolemic rats. Our experimental results show that garlic may beneficially affect two risk factors for atherosclerosis--hyperlipidemia and hypertension.

The antihypertensive effect of garlic (Allium sativum) in the rat two-kidney--one-clip Goldblatt model.

A study was designed to elucidate the antihypertensive effect of garlic in the two-kidney--one-clip (2K-1C) Goldblatt model. Since the hypertension in this model depends largely on the increasing concentrations of vasopressor agents (prostaglandins and angiotensin II) there is a strong indication that reducing these factors could contribute in controlling the pathological rise in blood pressure. In this study, single or multiple doses of 0.5 ml of aqueous extract of garlic were given orally to 2K-1C rats. The data shows that the single dose of garlic used had a maximum antihypertensive effect 2-6 h after administration. The residual effect of this single dose continued for up to 24 h. The multiple dose of garlic appeared to be effective in restraining the expected rise in blood pressure that normally occurs in 2K-1C rats. Switching multiple-dose treatments halfway through the experiment further strengthened the findings. The study suggests that garlic does have an effective antihypertensive ability, and may be used as a supplementary and natural remedy in cases of unilateral renovascular hypertension.

Distention of the lateral intercellular spaces (LIS) in the proximal tubule cells of the non-stenosed kidney of the 2K-1C Goldblatt model of hypertension as evidence of pressure diuresis.

This study shows the development of two major deformities in the non-stenosed kidney of the 2K-1C Goldblatt model; namely the widening of the LIS and the enlargement of the basilar interdigitations of the proximal tubule cells. These deformities were much less in the 2K-1C animals treated with the angiotensin I converting enzyme inhibitor (AICEI) cilazapril. From these findings it is suggested that the non-stenosed kidney is operating under the diuretic effect of the elevated systemic blood pressure (SBP) via an increase in the renal interstitial hydrostatic pressure (RIHP). Therefore, the AII antidiuretic effect is masked by the diuretic effect of the elevated SBP. The suggested rise in urine output fits well with the idea that kidneys lose water and sodium when SBP increases enormously. Therefore, in this model of hypertension, the non-stenosed kidney tries to lower SBP by losing water and sodium, an excretion behavior which is opposite to that of the stenosed kidney. Thus, the rise in SBP in this model is probably due to an increase in the vascular peripheral resistance rather than fluid accumulation.

Chemopreventive effects of cabbage on 7,12-dimethylbenz(a)-anthracene-induced hepatocarcinogenesis in toads (Bufo viridis).

Hepatocellular carcinoma was induced in the toad, Bufo viridis, in 29 out of 100 cases by the administration of 0.5 mg of 7,12-dimethylbenz(a)anthracene (DMBA)/toad, 3 times/week for 12 weeks. In contrast, toads treated with DMBA and cabbage diet 1 or 2 ml (3 h prior to the carcinogen)/toad, every day for 12 weeks showed a lower incidence of liver tumors: 15 and 12 cases out of 100. However, cabbage diet (2 ml/toad, every day for 12 weeks) was ineffective when administered 3 h after the carcinogen (DMBA) in 27 out of 100 cases. Neither tumor growth nor neoplastic changes were observed in toads treated with olive oil alone or with cabbage diet. It is concluded that a cabbage diet during initiation has an inhibitory effect on hepatocarcinogenesis in toads.

A comparison of the actions of cilazapril in normal, dietary sodium-depleted and two-kidney, one clip Goldblatt hypertensive anaesthetised rats.

OBJECTIVE: This study aimed to examine the role of the renin-angiotensin system in the regulation of kidney haemodynamic and excretory function when angiotensin II levels were modestly and markedly raised. DESIGN: Three groups of male Sprague-Dawley rats were used: control rats fed a sodium-replete diet; rats fed a sodium-deficient diet for 2 weeks; and two-kidney, one clip (2K1C) Goldblatt hypertensive rats, 4-5 weeks postclipping. METHODS: The rats were acutely anaesthetized with sodium pentobarbitone and prepared for renal function measurements. The converting enzyme inhibitor, cilazapril, was then infused at increasing dose levels to progressively block the renin-angiotensin system. RESULTS: Cilazapril did not affect blood pressure in sodium-replete animals; it raised RBF and increased water and sodium excretion. In dietary sodium-depleted rats, cilazapril decreased blood pressure and increased RBF, water and sodium excretion at the lower doses of the drug; however, at vasodepressor doses, water and sodium excretion fell towards baseline values. In 2K1C Goldblatt hypertensive rats, cilazapril maximally decreased blood pressure whilst the non-clipped kidney blood flow, filtration rate and fluid excretion rates were similar to dietary sodium-depleted rats; in contrast, the clipped kidney filtration rate was well maintained and fluid excretion was raised in a dose-related fashion. CONCLUSION: These results show that during gradual cilazapril administration, renal function is well preserved in 2K1C Goldblatt hypertensive rats when pressure is progressively reduced.

Hyperhydration with glycerol solutions.

Glycerol was tested as an agent to promote hyperhydration of male and female subjects. Series I experiments involved ingesting 0.5, 1.0, or 1.5 g glycerol/kg body wt and within 40 min drinking 0.1% NaCl, 21.4 ml/kg. In series II, 1.0 g glycerol/kg body wt was ingested at time 0, and 25.7 ml/kg of 0.1% NaCl was ingested over a 3.5-h period. Experiments were of 4-h duration and included controls without glycerol as each subject served as his/her control. Blood samples were taken at 40- or 60-min intervals for hemoglobin (Hb), hematocrit (Hct), plasma osmolality, glycerol, and multiple blood chemistry analyses. Urine was collected at 60-min intervals. Glycerol ingestion increased plasma osmolality for 2 h and reduced the total 4-h urine volume. There were no significant changes in Hb or Hct as a result of the glycerol or excess fluid intake. This study demonstrates that glycerol plus excess fluid intake can produce hyperhydration for at least 4 h.