Adverse effects of tempol on hidrosaline balance in rats with acute sodium overload.

We studied the effects of tempol, an oxygen radical scavenger, on hydrosaline balance in rats with acute sodium overload. Male rats with free access to water were injected with isotonic (control group) or hypertonic saline solution (0.80 mol/l NaCl) either alone (Na group) or with tempol (Na-T group). Hydrosaline balance was determined during a 90 min experimental period. Protein expressions of aquaporin 1 (AQP1), aquaporin 2 (AQP2), angiotensin II (Ang II) and endothelial nitric oxide synthase (eNOS) were measured in renal tissue. Water intake, creatinine clearance, diuresis and natriuresis increased in the Na group. Under conditions of sodium overload, tempol increased plasma sodium and protein levels and increased diuresis, natriuresis and sodium excretion. Tempol also decreased water intake without affecting creatinine clearance. AQP1 and eNOS were increased and Ang II decreased in the renal cortex of the Na group, whereas AQP2 was increased in the renal medulla. Nonglycosylated AQP1 and eNOS were increased further in the renal cortex of the Na-T group, whereas AQP2 was decreased in the renal medulla and was localized mainly in the cell membrane. Moreover, p47-phox immunostaining was increased in the hypothalamus of Na group, and this increase was prevented by tempol. Our findings suggest that tempol causes hypernatremia after acute sodium overload by inhibiting the thirst mechanism and facilitating diuresis, despite increasing renal eNOS expression and natriuresis.

Role of angiotensin II and oxidative stress in renal inflammation by hypernatremia: benefits of atrial natriuretic peptide, losartan, and tempol.

The body regulates plasma sodium levels within a small physiologic range, despite large variations in daily sodium and water intake. It is known that sodium transport in the kidneys plays an important role in hypoxia, being the major determinant of renal oxygen consumption. Tubular epithelial cell hypoxia is an important contributor to the development of renal inflammation, and the damage may progress to structural injury, ending in acute renal failure. In this review, we will summarize the renal inflammatory effects of high acute plasma sodium (acute hypernatremia), and the molecular mechanisms involved. We will also discuss recent findings related to the role of oxidative stress and angiotensin II (Ang II) in the pathogenesis of renal injury. We will comment on the effects of agents used to prevent or attenuate the inflammatory response, such as the atrial natriuretic peptide, the superoxide dismutase mimetic - tempol, and losartan.

Signaling pathways involved in renal oxidative injury: role of the vasoactive peptides and the renal dopaminergic system.

The physiological hydroelectrolytic balance and the redox steady state in the kidney are accomplished by an intricate interaction between signals from extrarenal and intrarenal sources and between antinatriuretic and natriuretic factors. Angiotensin II, atrial natriuretic peptide and intrarenal dopamine play a pivotal role in this interactive network. The balance between endogenous antioxidant agents like the renal dopaminergic system and atrial natriuretic peptide, by one side, and the prooxidant effect of the renin angiotensin system, by the other side, contributes to ensuring the normal function of the kidney. Different pathological scenarios, as nephrotic syndrome and hypertension, where renal sodium excretion is altered, are associated with an impaired interaction between two natriuretic systems as the renal dopaminergic system and atrial natriuretic peptide that may be involved in the pathogenesis of renal diseases. The aim of this review is to update and comment the most recent evidences about the intracellular pathways involved in the relationship between endogenous antioxidant agents like the renal dopaminergic system and atrial natriuretic peptide and the prooxidant effect of the renin angiotensin system in the pathogenesis of renal inflammation.

Acute sodium overload produces renal tubulointerstitial inflammation in normal rats.

The aim of the present study was to determine whether acute sodium overload could trigger an inflammatory reaction in the tubulointerstitial (TI) compartment in normal rats. Four groups of Sprague-Dawley rats received increasing NaCl concentrations by intravenous infusion. Control (C): Na+ 0.15 M; G1: Na+ 0.5 M; G2: Na+ 1.0 M; and G3: Na+ 1.5 M. Creatinine clearance, mean arterial pressure (MAP), renal blood flow (RBF), and sodium fractional excretion were determined. Transforming growth factor beta1 (TGF-beta1), alpha-smooth muscle actin (alpha-SMA), RANTES, transcription factor nuclear factor-kappa B (NF-kappaB), and angiotensin II (ANG II) were evaluated in kidneys by immunohistochemistry. Animals with NaCl overload showed normal glomerular function without MAP and RBF modifications and exhibited a concentration-dependent natriuretic response. Plasmatic sodium increased in G2 (P < 0.01) and G3 (P < 0.001). Light microscopy did not show renal morphological damage. Immunohistochemistry revealed an increased number of ANG II-positive tubular cells in G2 and G3, and positive immunostaining for NF-kappaB only in G3 (P < 0.01). Increased staining of alpha-SMA in the interstitium (P < 0.01), TGF-beta1 in tubular cells (P < 0.01), and a significant percentage (P < 0.01) of positive immunostaining for RANTES in tubular epithelium and in glomerular and peritubular endothelium were detected in G3 > G2 > C group. These results suggest that an acute sodium overload is able 'per se' to initiate TI endothelial inflammatory reaction (glomerular and peritubular) and incipient fibrosis in normal rats, independently of hemodynamic modifications. Furthermore, these findings are consistent with the possibility that activation of NF-kappaB and local ANG II may be involved in the pathway of this inflammatory process.

Impaired response to insulin associated with protein kinase C in chronic fructose-induced hypertension.

A fructose-enriched diet induces an increase in blood pressure associated with metabolic alterations in rats. Our hypothesis was that an increase in protein kinase C (PKC) activation, reported in the acute period of fructose overload, and an impaired vessel's response to vasoactive substances contribute to maintain elevated blood pressure levels in the chronic period. The aims of this study were to investigate in this animal model of hypertension: (1) if the increase in PKC activation was also found in the chronic stage; (2) the involvement of nitric oxide and insulin in the vessel's response; and plasma atrial natriuretic factor and nitrites/nitrates (nitric oxide metabolites) behavior. We evaluated the effects of: PKC-stimulator 12,13-phorbol dibutyrate, phenylephrine, insulin, nitric oxide synthase-inhibitor NG-nitro-L-arginine methyl esther (L-NAME) and PKC-inhibitor Calphostin C on aortic rings responses of Sprague-Dawley rats: fructose-fed and control. The fructose-fed group showed higher contractility to 12,13-phorbol dibutyrate than the control group in aortic rings pre-incubated with insulin, and this difference disappeared with L-NAME. The response to phenylephrine in rings pre-incubated with Calphostin C was decreased in the fructose-fed group and increased with Calphostin C plus L-NAME. Fructose-fed rats showed higher levels of plasma atrial natriuretic factor and nitrites/nitrates than controls. In conclusion, chronic fructose feeding seems to develop an impaired response to insulin, dependent on nitric oxide, suggesting a PKC alteration. Vasorelaxant agents, such as atrial natriuretic factor and nitric oxide, would behave as compensatory mechanisms in response to high blood pressure.

Serotonin hypersensitivity in aorta of two kidney-two clip hypertensive rats: calcium contribution and prostanoids-nitric oxide interactions.

Previous studies from our own laboratory have shown that abdominal aorta rings from two kidney - two clip hypertensive rats (HT) develop hypersensitivity to serotonin (SER) which is related to a decreased nitric oxide (NO) availability and enhanced thromboxane A2 production. In the present study we investigated whether calcium and prostanoid-NO interactions are involved in these findings. To this purpose, the aortic responses to SER were analyzed in calcium-free medium and in calcium-depleted aorta placed in normal medium. Moreover, effects of ridogrel (RID, an antagonist of TxA 2/PGH2 receptors and inhibitor of thromboxane synthetase) were analysed by cumulative dose-response curves to SER in the presence and in the absence of the NO synthase inhibitor N(omega)-nitro-L-arginine (NOLA). Vascular responses to SER in vessels from HT rats were associated with increased intracellular calcium mobilization. In addition, hypersensitivity to SER in HT group respect to sham group (SH) disappeared in the presence of RID, NOLA and RID plus NOLA. RID decreases the maximum tension to SER and this effect was prevented by NOLA. This inhibition was of a greater magnitude in rings from sham rats (SH): 34 +/- 6% than in HT rats: 15 +/- 6% (p < 0.05). Besides, RID decreased the sensibility to SER in the presence of NOLA only in the HT group. In conclusion, the present study suggests that SER hypersensitivity observed in HT rats is related to a facilitated intracellular calcium mobilization and enhanced TxA2-endoperoxide response. Changes in membrane SER-gated calcium channels opening are observed only during the early hypertensive period. Besides, the lower depressor effect of RID on the maximal tension to SER in aorta rings from HT rats are related with a decreased NO availability in this model of renovascular hypertension.

Effect of oral L-arginine administration for three weeks in two kidney-two clip hypertensive rats.

Nitric oxide (NO) has been identified as an effective vascular relaxant. This study analyses the contribution of the precursor L-arginine (L-arg) by oral administration in two kidney-two clip hypertension in the rat (2K-2C). Two groups were studied: sham (SH, n=21) and hypertensive (HT, n=15). After 4 weeks of surgery, a group of rats remained as controls (SHc and HTc, respectively), while others were supplemented with L-arg (1.25 g/L) in drinking water (SHa and HTa) for 3 weeks. Blood pressure was significantly increased in 2K-2C rats but remained unchanged after L-arg treatment. Plasma nitrite/nitrate concentrations were not different among groups. The contractile response of aorta to KCl, serotonin and the protein kinase C (PKC) stimulant, phorbol 12,13-dibutyrate (PDBu) was also evaluated. Higher contractile responses to PDBu (p<0.001) and lower relaxation to acetylcholine (Ach 10(-6) M, p<0.05 and 10(-5)M, p<0.02) were observed in aortic rings of HTc vs SHc; L-arg supplementation significantly diminished tension development to all agonists (p<0.05) but failed to modify the lower relaxation to Ach in HTa. Thromboxane (TxA(2)) - synthesis in rings of HTc was higher than in SHc under basal conditions (p<0.05). In the groups with supplement of L-arg, PDBu significantly stimulated prostacyclin (PGI(2)) synthesis more in HTa rats than in SHa ones (p<0.05). To conclude: 1) L-arg fails to modify hypertension development in 2K-2C rats; and 2) L-arg exerts a beneficial effect on the vascular wall, by reducing contractility in rings from HTa rats; it also improved PGI(2) synthesis under PDBu stimulation. 3) greater PKC activation and TxA(2) production rather than lower NO availability might result in systemic hypertension in 2K-2C rats.

Potential role of glycerol leading to rat fructose hypertension.

A fructose-enriched diet promotes hypertension in rats. We thought that an enhancement of the glycolytic and/or lipid disorder (s) that raise blood pressure could be the cause. Therefore, we studied 4 groups of Sprague-Dawley rats (+/-200 g): (1) control rats received a standard diet and tap water; (2) the glycerol group of rats received a standard diet and 0.54 mol/L glycerol in tap water; (3) the fructose group was given a fructose-enhanced diet (chow had 55% fructose instead of dextrin) and tap water; and (4) the fructose-glycerol group was given the fructose-enhanced diet and 0. 54 mol/L glycerol in drinking water. At the end of the second week, the findings were as follows. Blood pressure was 149+/-2 mm Hg in the fructose-glycerol group versus 129+/-2 (P<0.001), 131+/-2 (P<0. 001), and 140+/-3 (P<0.005) mm Hg in the control, glycerol, and fructose groups, respectively. Insulinemia was higher in the fructose-glycerol group than the control (P<0.001), glycerol (P<0. 001), and fructose groups (P<0.001); triglyceridemia was higher in the fructose-glycerol (P<0.02), fructose (P<0.05), and glycerol groups (P<0.02) than the control group. Thoracic aorta rings showed a lower ED(50) to 12,13-phorbol dibutyrate in the fructose-glycerol group than in the control (P<0.001), glycerol (P<0.002), and fructose groups (P<0.001). In conclusion, glycerol-fructose administration resulted in hypertriglyceridemia, hyperinsulinemia, and increased vascular sensitivity to 12,13-phorbol dibutyrate (with respect to the control group), and significantly greater expression of protein kinase C alpha and betaII (with respect to the glycerol group).

Atrial natriuretic factor in two kidney--two clip renovascular hypertension in the rat.

Hig levels of circulating atrial natriuretic factor (ANF) have been reported in several physiopathologic conditions like hypertension, heart and renal failure, pregnancy and high sodium intake. Nevertheless, neither relationships with water-sodium space regulation nor the role of an ANF vascular relaxant effect have been yet defined. The aim of present experiments was to characterize the contribution of circulating ANF and its vascular relaxing effects in the two kidney-two clip (2K2C) experimental model of renovascular hypertension. Complementary, plasma metabolites nitrite/nitrate of nitric oxide (NO) was examined because of mediation for both (NO an ANF) through cGMP. Three results showed (two-four weeks after surgery): indirect systolic blood pressure (mmHg), 186 +/- 4 in HT and 122 +/- 1 in SH (p < 0.001); a significant increase of plasma ANF (fmol/ml) in HT (n = 7, 1221 +/- 253) vs. SH (n = 9, 476 +/- 82; p < 0.02). Nitrate/nitrite plasma concentrations (mumol/l) were mpt different between SH and. The relaxant effect of ANF (10(-9), 10(-8) and 10(-7) M) on phenylephrine (3,5 x 10(-6) M) contracted rings from HT rats was smaller than SH rats (10(-8) M, p < 0.05). Contractions to phorbol 12, 13-dibutyrate (seven weeks after surgery) were significantly higher in rings from HT rats (p < 0.001). We conclude: 1) in addition to decreased granularity in atrial myocardiocytes, high circulating values of ANF here described suggest an increased turnover of the peptide in 2K2C hypertensive rats; 2) lower significant vascular relaxant effects in HT rats would indicate down regulation of ANF receptors in this model; the latter would derive from high plasma ANF concentration and, tentatively, because of greater activity of protein kinase C in the vascular wall; 39 similar values of plasma nitrite/nitrate in SH and HT rats would indicate a comparable NO circulating availability in both groups.

Nitric oxide and superoxide anions in vascular reactivity of renovascular hypertensive rats.

The present study intends to define the role of the endothelium derived relaxing factor nitric-oxide (EDRF-NO) and the reactive oxygen intermediates in hypersensitivity to 5-hydroxytryptamine (5-HT) observed in abdominal aorta rings of two kidney-two clip hypertensive rats. Methylene Blue (which blocks production of cGMP by EDRF-NO) and Nw-nitro-L-arginine (which inhibits EDRF-NO synthesis), both shifted 5-HT dose-response curves to the left and completely abolished the differences in sensitivity to the agonist. The aortic perfusion with Krebs-Alcohol 20% (v/v) suppressed vascular relaxation to Ach (10(-5) M) and also abolished differences in sensitivity to 5-HT. These results suggest that a lower availability of EDRF-NO accounts for a higher 5-HT sensitivity in vessels of hypertensive rats. On the contrary, ridogrel (inhibitor of tromboxane-synthase and blocker of PGH2 and TxA2 receptors) did not suppress the hypersensitivity to 5-HT. In addition, since the superoxide anion (O2-) inactivates EDRF-NO, the effects of Superoxide dismutase (SOD) and Catalase (CAT) added in the bath were analyzed. Significant changes in sensitivity (P < 0.005) were found only for vessels of hypertensive rats (SOD depressing and CAT increasing sensitivity to 5-HT). Complementary, SOD activity was evaluated in the aorta homogenates and was found to be significantly lower in the hypertensive rats [(differences between hypertensive and sham rats, mU.mg wet weight tissue-1: 7 days after clipping, -183 +/- 67 (n = 11), P < 0.02; 21 days, -160 +/- 70 (n = 9), p < 0.05]. Results would indicate: 1. Lower EDRF-NO availability in vessels of the hypertensive animals which would account for higher sensitivity to 5-HT; 2. Such a lower EDRF-NO might depend, in part, upon its greater inactivation by O2- anions; 3. A greater presence of O2- anions in the vessels of hipertensive rats that might be favored by the lower SOD activity concentration in the vascular wall.

Ultrastructural study of atrial specific granules in experimental renovascular hypertension elicited by the constriction of both renal arteries.

The heart has an endocrine activity which depends on the secretion of a natriuretic, diuretic and hypotensive factor contained in osmophilic, secretory granules localized in the myocardiocytes and called "atrial specific granules" (the atrial natriuretic factor, ANF). In this paper, the relationship between these specific granules and renovascular hypertension elicited by the constriction of both renal arteries was investigated at the electron microscope level during the acute, subacute and chronic phases of hypertension. Male Wistar CHbb THOM rats were divided in three groups: 1) clipped rats; 2) sham operated rats; 3) ether anesthesia as unique manoeuver 48 h before decapitation. Blood pressure increased progressively after the constriction of both renal arteries. The atrial specific granules were not affected by ether anesthesia alone; 48-72 h after clipping the granules almost disappeared and this situation persisted up to the 6th week. In sham operated rats the picture was very similar to the clip rats 48 and 72 h after surgery (severe granule disappearance); in contrast, at one, two and six weeks after surgery, the granularity of cardiomyocytes in sham rats was absolutely restored. It is concluded that: 1) similarities in morphology of atrial specific granules in sham and clip rats 48 and 72 h after surgery would suggest that stress plays a primary role in determining the observed images; 2) thereafter, the contrast between sham and clip rats 1, 2 and 6 weeks after surgery would indicate that the ANF is linked to the subacute and chronic regulation of renovascular hypertension.

Ultrastructural study of atrial specific granules in experimental renovascular hypertension elicited by the constriction of both renal arteries

El corazón tiene una actividad endocrina que depende de la secreción de un factor nafriurético, diurético e hipotensor contenido en gránulos osmiófilos secretorios localizados en los miocardiocitos y llamados " granulos atriales específicos" (atrial natriuretic factor, ANF). En este trabajo se investigó al microscópio electrónico la relación existente entre los gránulos atriales específicos y la hipertensión renovascular provocada por constricción de ambas arterias renales, examinándose los períodos agudo, subagudo y crónico de hipertensión. Se usaron ratas macho, Wistar CHbb Thom. Los animales fueron divididos en tres grupos: 1) ratas con compresión bilateral de la arteria renal; 2) ratas con operación simulada; 3) ratas con anestesia con éter como única maniobra, 48 hs antes de la decapitación. La presión arterial aumentó progresivamente después de la constricción de las arterias renales. Los gránulos atriales específicos no fueron afectados por la anestesia con éter. Por el contrário 48-72h después de la compresión de las arterias renales los gránulos atriales específicos prácticamente desaperecieron y esta situación persistía 1, 2 y 6 semanas después. En las ratas con operación simulada se observó un cuadro similar a las ratas con constricción arterial (severa desaparición de los gránulos) pero 1, 2 y 6 semanas más tarde la granularidad de los cardiomiocitos se había restaurado completamente. Se concluye: 1) la similitud de la respuesta en ratas con constricción de ambas arterias renales y en ratas con operación simulada 48-72 h después de la intervención sugiere que el estrés desempeña un papel inicial en los resultados observados. 2) el contraste observado 1, 2 y 6 semanas después entre ratas con constricción arterial pemanente y ratas con operación simulada indicaría que el factor natriurético atrial está vinculado con la regulación subaguda y crónica de la hipertensión renovascular

Ultrastructural study of atrial specific granules in experimental renovascular hypertension elicited by the constriction of both renal arteries.

The heart has an endocrine activity which depends on the secretion of a natriuretic, diuretic and hypotensive factor contained in osmophilic, secretory granules localized in the myocardiocytes and called [quot ]atrial specific granules[quot ] (the atrial natriuretic factor, ANF). In this paper, the relationship between these specific granules and renovascular hypertension elicited by the constriction of both renal arteries was investigated at the electron microscope level during the acute, subacute and chronic phases of hypertension. Male Wistar CHbb THOM rats were divided in three groups: 1) clipped rats; 2) sham operated rats; 3) ether anesthesia as unique manoeuver 48 h before decapitation. Blood pressure increased progressively after the constriction of both renal arteries. The atrial specific granules were not affected by ether anesthesia alone; 48-72 h after clipping the granules almost disappeared and this situation persisted up to the 6th week. In sham operated rats the picture was very similar to the clip rats 48 and 72 h after surgery (severe granule disappearance); in contrast, at one, two and six weeks after surgery, the granularity of cardiomyocytes in sham rats was absolutely restored. It is concluded that: 1) similarities in morphology of atrial specific granules in sham and clip rats 48 and 72 h after surgery would suggest that stress plays a primary role in determining the observed images; 2) thereafter, the contrast between sham and clip rats 1, 2 and 6 weeks after surgery would indicate that the ANF is linked to the subacute and chronic regulation of renovascular hypertension.

Ultrastructural study of atrial specific granules in experimental renovascular hypertension elicited by the constriction of both renal arteries

El corazón tiene una actividad endocrina que depende de la secreción de un factor nafriurético, diurético e hipotensor contenido en gránulos osmiófilos secretorios localizados en los miocardiocitos y llamados " granulos atriales específicos" (atrial natriuretic factor, ANF). En este trabajo se investigó al microscópio electrónico la relación existente entre los gránulos atriales específicos y la hipertensión renovascular provocada por constricción de ambas arterias renales, examinándose los períodos agudo, subagudo y crónico de hipertensión. Se usaron ratas macho, Wistar CHbb Thom. Los animales fueron divididos en tres grupos: 1) ratas con compresión bilateral de la arteria renal; 2) ratas con operación simulada; 3) ratas con anestesia con éter como única maniobra, 48 hs antes de la decapitación. La presión arterial aumentó progresivamente después de la constricción de las arterias renales. Los gránulos atriales específicos no fueron afectados por la anestesia con éter. Por el contrário 48-72h después de la compresión de las arterias renales los gránulos atriales específicos prácticamente desaperecieron y esta situación persistía 1, 2 y 6 semanas después. En las ratas con operación simulada se observó un cuadro similar a las ratas con constricción arterial (severa desaparición de los gránulos) pero 1, 2 y 6 semanas más tarde la granularidad de los cardiomiocitos se había restaurado completamente. Se concluye: 1) la similitud de la respuesta en ratas con constricción de ambas arterias renales y en ratas con operación simulada 48-72 h después de la intervención sugiere que el estrés desempeña un papel inicial en los resultados observados. 2) el contraste observado 1, 2 y 6 semanas después entre ratas con constricción arterial pemanente y ratas con operación simulada indicaría que el factor natriurético atrial está vinculado con la regulación subaguda y crónica de la hipertensión renovascular (AU)

Contrasting effects of norepinephrine and 5-hydroxytryptamine on contractility of abdominal aorta of two kidney-two clip hypertensive rats. Effects of inhibitors of arachidonic acid metabolic enzymes.

This study intends to: 1) define reactivity in vessels of two kidney-two clip (2K2C) hypertensive rats (6-11 days after clipping); 2) determine the possible involvement of prostaglandins in modulating contractile vascular responses. Cumulative dose-response curves to norepinephrine (NE), 5-hydroxytryptamine (5-HT) and potassium chloride (KCl) were elicited on helical strips of abdominal aorta both in the absence and in the presence of prostacyclin synthetase (transylcypromine, TCP, 0.25mM) or cyclooxygenase (indomethacin, IND, 0.014 mM and acetylsalicylic acid, ASA, 0.20 mM) inhibitors Vessels of hypertensive animals developed significantly less tension to NE (n = 21) but higher tension and lower ED50 in response to 5-HT (n = 9) than sham control rat vessels. Force development to KCl (n = 9) was not statistically different between hypertensive and sham vessels. Vascular responses were decreased with the inhibitors, but the contrasting effects of NE and 5-HT on clip vessels were maintained. Threshold doses of PGE2 significantly reversed the effect of IND but not that of TCP on NE responses. Threshold doses of PGI2 had no significant effect on NE and 5-HT responses under TCP. The results would indicate: 1) different functional alterations for contractions to NE and 5-HT appear to have developed in vessels of 2K2C hypertensive rats; 2) PGE2 effectively contributes to modulation of NE responses in rat aorta strips; 3) these experiments suggest that prostaglandins do not play a significant role in the altered contractility of vessels in hypertensive rats.

Water and exchangeable sodium in Goldblatt two-kidney, two-clip hypertensive rats.

Exchangeable 22Na (ExNa), total body water (TBW) and the inulin space (InSp) were determined in two-kidney, two-clip (2K-2C) hypertensive and sham operated (normotensive) control rats 6-8 weeks after surgery. TBW (ml/kg lean body weight) was the same in hypertensive and sham rats. In contrast, ExNa (mEq/kglbw) and InSp (ml/kglbw) significantly increased (p less than 0.01) in rats whose hypertension did not exceed 170 mmHg. Consequently, sham, moderate hypertensive (less than 170 mmHg) and severe hypertensive (less than 170 mmHg) animals showed equal TBW but differed in body water distribution in that moderately hypertensive animals displayed a redistribution of water in favor of the extracellular space.

Prostacyclin (PGI2) synthesis in the vascular wall of rats with bilateral renal artery stenosis.

The ability of vessels (rings of arteries and vena cava) to synthesize prostacyclin (PGI2) "in vitro" was analyzed in the initial (6-day) and chronic (6-week) phase of two-kidney, two clip hypertension. Male Wistar CHbb THOM rats were used. Tissues were incubated for two hours in Krebs solution containing 14C-arachidonic acid as exogenous substrate. Specimens (in benzene-ethanol 4:1 vol/vol) and the unlabeled standard solutions of arachidonic acid, 6-keto PGF1 alpha, PGF2 alpha, and PGE2, were spotted on silica gel-G plates for thin layer chromatography. Conversion of 14C-arachidonic acid to stable metabolite 6-keto PGF1 alpha was used as an index of PGI2 synthesis. Results shown: 1) PGI2 is the major PG synthesized by the rat artery wall; 2) PGI2 synthesis was increased 2.4 times in the initial 6-day period of development of renovascular hypertension (RH); 3) no changes in PGI2 production were observed in arteries during the chronic 6-week period of RH; 4) abdominal vena cava has little or no capacity to produce PGI2. As PGI2 is a potent vasodilator, higher production by arteries during the 6-day period suggests that prostacyclin could play a modulator role on peripheral resistance during the initial phase of renal hypertension.

Initial mechanisms in hypertension after bilateral renal ischemia in the rat.

Cumulative water- and electrolyte balance, plasma creatinine (PC), plasma renin activity (PRA), urinary prostaglandins (PGs) E2, and F2alpha and kallikrein (K) were studied in 40 male Wistar CHbb THOM rats (250 +/- 4 g SE). A solid silver clip (0.25 mm lumen) was applied to both renal arteries in 18 animals; 13 rats were sham-operated and nine remained intact. The analyses were performed during a control period and up to 10 days after surgery. Blood pressure (BP) recorded on the 10th and 12th day of the study increased significantly in clipped rats with respect to sham rats (p less than 0.001);PC and PRA measured on the 11th day were not significantly different. A positive cumulative water "balance" )p less than 0.01) and sodium balance (p less than 0.02) was found in clipped rats when compared with sham rats in the first 5 days of the experimental period. Significantly higher values of PGE2 urinary excretion were observed in sham rats vs clipped rats on the 2nd and 5th day after surgery (p less than 0.02). On the 2nd day after surgery, K urinary excretion was significantly lower in clipped rats than in sham rats (p less than 0.02). No significant changes were observed in PGF2alpha excretion. The absence of significant difference in PRA 10 days after bilateral renal artery stenosis points to a lack of any fundamental role of circulating angiotensin II at this stage of the development of hypertension. The significant water- and salt retention in the first 5 days after clipping suggests that it might be involved in the pathogenesis of this model. Early changes in PGs E2 and F2alpha and K appear to be related more to intrarenal adjustments soon after surgery than to the increase in BP.