Ventricular myosin and creatine-kinase isoenzymes in hypertensive rats treated with captopril

In the myocardium, myosin and creatine kinase isoforms possess different capacities for using O2 and energy-rich phosphates. We studied electrophoretically the distribution of these isoforms in 19 hypertensive rats (two-kidney, one clip model of hypertension) and in age-matched controls. After 6 weeks of hypertension, seven rats were treated with captopril (2 mg/kg daily) for 4 weeks, six were left hypertensive for another 4 weeks, and the remaining rats were killed under ether anesthesia. In the latter, ventricular mass was significantly higher than in controls; V3 isomyosin was 32.3 +/- 6.8% versus 0%, and both creatine kinase-MB and -BB were increased at the expense of creatine kinase-MM (creatine kinase-MB = 29 +/- 2.8% vs. 14.7 +/- 1.8%, p less than 0.001; creatine kinase-BB = 3.1 +/- 0.6% vs. 1.7 +/- 0.8%, p less than 0.001). After 10 weeks of hypertension, ventricular mass, V3 isomyosin, and both creatine kinase-MB and -BB isoforms were found to be persistently higher than in controls. At the same time, captopril-treated rats showed reduced but not normalized blood pressure levels, normalized ventricular mass, and prevalence of the V1 isomyosin (56.9 +/- 22% vs. 47.9 +/- 23.8% in normotensive controls, p = NS). However, higher levels of creatine kinase-MB and -BB were still found in these rats in comparison with the normotensive controls (creatine kinase-MB = 22.4 +/- 5.4% vs. 15.8 +/- 2.8%, p less than 0.025; creatine kinase-BB = 2.3 +/- 0.1% vs. 1.8 +/- 0.3%, p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Decreased cardiac concentration of cGMP kinase in hypertensive animals. An index for cardiac vascularization?

Cyclic GMP (cGMP) kinase is intimately involved in the regulation of vascular smooth muscle tone. Its tissue concentration was determined in normotensive and hypertensive rats by use of monospecific anti-cGMP kinase antibodies. Hearts of spontaneously hypertensive rats and renovascular (Goldblatt II) hypertensive rats contained half the concentration of cGMP kinase than those of the respective normotensive animals. The increase in blood pressure and the resulting left ventricular hypertrophy were correlated inversely with the left ventricular cGMP kinase concentration. This decrease was specific for the left ventricle and was not observed in other tissues. In addition, the cardiac concentration of cGMP kinase was unchanged in hyperthyroid animals that had comparable left ventricular hypertrophy and mild hypertension. This suggested that in severe renovascular hypertension the decrease in cardiac cGMP kinase concentration is caused by a relative lack of cardiac vessel growth during the development of hypertrophy. In agreement with this conclusion, immunohistochemistry of cardiac cross sections showed that cGMP kinase was exclusively located in cardiac vessels. In support of this localization, the maximal arterial blood flow of heart, liver, skeletal muscle, and kidney correlated excellently with the cGMP kinase content of the respective organ. These results suggest that the cGMP kinase concentration of nonsmooth muscle tissues depends on the amount of organ-specific vascular smooth muscle and may be used as an index for the vascularization of these organs.

Functional and biochemical analyses of isolated rat hearts in renal and reversed renal hypertension

The present study evaluates cardiac function, plasma renin activity (PRA) and left ventricular (LV) myosin isoenzymes in untreated two-kidney, one-clip Goldblatt hypertensive rats (2KIC) and in 2KIC treated with felodipine and metoprolol. Normotensive rats (NCR) and another group of 2KIC, in which the renal artery constriction was removed (UC-2KIC), were also investigated. Cardiac performance was assessed by means of a working heart perfusion device, allowing also for measurements of myocardial oxygen consumption. Following antihypertensive therapy and unclipping, blood pressure became close to normotensive levels. PRA remained equally elevated in treated and untreated 2KIC, but became practically normalized after unclipping. Relative LV weight in 2KIC increased 74% above that in NCR but in treated 2KIC increased by only 20%. In UC-2KIC LV hypertrophy became reversed, LV weight/body being about the same as in treated 2KIC. In treated 2KIC, coronary resistance at maximal dilatation was significantly reduced, implying prevention of hypertensive, structural coronary vascular changes, and optimal LV function was improved markedly in the lower range of perfusion pressures compared with untreated 2KIC. When, however, the hearts were challenged at a high pumping resistance (perfusion pressure), LV function was similar in untreated and treated 2KIC. Myocardial oxygen consumption for given levels of stroke work was significantly lower in treated than in untreated 2KIC. The myosin isoenzyme pattern in the LV of 2KIC was shifted, with significantly higher amounts of VM-3 than in NCR. This shift was normalized by antihypertensive therapy or by unclipping. In conclusion, antihypertensive therapy with felodipine and metoprolol prevents the development of coronary vascular and left ventricular hypertrophy in 2KIC. This may contribute to enhance cardiac performance at low aortic pressure. The lack of improvement in optimal cardiac performance (at high aortic pressure) implies that the hypertensive state per se, rather than extent of pressure elevation, cardiac hypertrophy, or changes of LV isoenzymes, determines the reduced cardiac function in renal hypertensive rats (Friberg & Nordborg 1986).

Changes in plasma ACE activity during the development and reversal of one-kidney, one clip hypertension in rats

Plasma angiotensin converting enzyme (ACE) activity was studied during the development and the reversal of one-kidney, one clip (1K1C) renal hypertension in rats (RHR). Plasma ACE activity was measured in RHR 1 (n = 11), 3 (n = 8), 6 (n = 12), 14 (n = 7), and 80-120 days (n = 17) after clipping. Plasma ACE activity (nmol/min/ml) was elevated (p less than 0.05) in chronic RHR (80-120 days; mean arterial pressure, MAP: 216 +/- 9 mmHg), being 142 +/- 14 (n = 17) vs. 100 +/- 3.2 (n = 20) for normotensive control rats (MAP: 116 +/- 3 mmHg), whereas no significant differences were observed at earlier times. Overactivity of the renin-angiotensin system (RAS) was demonstrated indirectly by the reduction of MAP (greater than 15 mmHg) in response to captopril (10 mg/kg, i.v.) only during the first 3 days after clipping and in chronic severely hypertensive rats. In another experiment, ACE activity in chronic RHR was measured serially before and 1, 6 and 24 hours after unclipping. Serial measurements of plasma ACE showed a progressive decrease from 145 +/- 26 to 122 +/- 21, 24 hours after unclipping (n = 7, p less than 0.05, paired Student t-test) when MAP was reduced from 204 +/- 15 to 113 +/- 7 mmHg. There was essentially no change during 24 hours from the initial values of RHR-sham (MAP: 206 +/- 5 mmHg, ACE: 140 +/- 19, n = 8) and normal rats-sham (MAP: 115 +/- 2 mmHg, ACE: 96 +/- 3, n = 6). These data provide further evidence that chronic renal hypertension is associated with important changes in the metabolism of vasoactive peptides.

Chronic angiotensin converting enzyme inhibition in the two-kidney, one clip hypertensive rat

Treatment with an angiotensin converting enzyme (ACE) inhibitor in renovascular hypertension produces acute effects on renal function; however, the long-term consequences of this are not known. We have studied the effect of chronic enalapril treatment on renal structure and function in the two-kidney, one clip model of renovascular hypertension in the rat. Four weeks after the left renal artery was clipped, the hypertensive rats were randomly allocated to treatment with enalapril, minoxidil or to no treatment. The drug dose was titrated for maximal hypotensive effect. After 4 months of treatment blood pressures were 129 +/- 3 mmHg (enalapril), 193 +/- 5 mmHg (minoxidil) and 220 +/- 4.8 mmHg (no treatment). Twelve months later survival was 84% (enalapril group), 48% (minoxidil group) and 15% (untreated group). Split kidney function (51Cr-EDTA clearance, ml/min) of the clipped kidneys was 0.0 (enalapril group), 0.26 +/- 0.23 (minoxidil group) and 0.74 +/- 0.13 (untreated group). The clipped kidney from enalapril-treated rats weighed 0.46 +/- 0.1 g, much less than in the minoxidil-treated group (1.2 +/- 0.07) or the untreated group (1.14 +/- 0.10). Enalapril treatment was withdrawn for 2 weeks in five rats, but the clipped kidney remained small and non-functional. Histological examination revealed marked interstitial fibrosis and tubular atrophy in clipped kidneys from both enalapril groups, in contrast to minor changes in the minoxidil-treated and the untreated groups. We conclude that chronic enalapril treatment of two-kidney, one clip hypertension in the rat improved survival and preserved total renal function, but was associated with irreversible fibrotic atrophy of the clipped kidney.

Role of vascular angiotensin converting enzyme in hypertension

The possible role of vascular angiotensin converting enzyme (ACE) in the maintenance of one-kidney, one clip (1-K,1C) hypertensive rats was studied in comparison with age-matched, one-kidney (1-K) normotensive rats. Mean blood pressure was elevated after partial occlusion of the left renal artery with unilateral nephrectomy, and the high blood pressure persisted for at least 11 weeks, whereas no significant changes in mean blood pressure were observed in 1-K rats. Plasma and vascular renin activities and plasma ACE activity did not differ between the two groups of rats, both 5 and 11 weeks after operation. In contrast, ACE activity in lung and mesenteric arteries in 1-K,1C hypertensive rats was significantly elevated 11 weeks after operation, but not 5 weeks after operation, compared with the matched 1-K normotensive rats. In addition, the decreases in mean blood pressure induced by ACE inhibition were significantly greater in 1-K,1C rats than those in 1-K rats. These results indicate that the elevation of vascular ACE activity may play an important role in the maintenance of high blood pressure and may result in hypotension in response to ACE inhibitors in the chronic stage of 1-K,1C hypertension.

Adrenal and vascular tyrosine hydroxylase activity in Goldblatt hypertension

To examine the role of the sympathetic nervous system in hypertension, the in vitro activity of tyrosine hydroxylase was examined in one-kidney, one clip (1K1C) and two-kidney, one clip (2K1C) hypertensive rabbits and their respective controls 2 weeks after surgical procedures. The in vitro activity of tyrosine hydroxylase provides a measure of catecholamine synthesis and serves as a biochemical index of activity of noradrenergic neurons and the adrenal medulla. Mean atrial pressure rose from 91.5 +/- 1.0 to 128.5 +/- 5.6 mm Hg (p less than 0.01) in the 1K1C group and from 91.8 +/- 1.3 to 106.5 +/- 5.0 mm Hg (p less than 0.02) in the 2K1C group, whereas no change in blood pressure was found in their respective controls. Adrenal tyrosine hydroxylase activity was increased 85% in the 1K1C group, as compared with values in one-kidney controls (from 11.8 +/- 1.5 to 21.8 +/- 1.1 pmol CO2/min/mg; p less than 0.0002), and was increased 49% in the 2K1C group, as compared with values in two-kidney controls (from 8.01 +/- 1.2 to 11.9 +/- 1.1 pmol CO2/min/mg; p less than 0.02). In the 1K1C group, proximal mesenteric tyrosine hydroxylase activity was decreased 46% compared with values in one-kidney controls (from 23.5 +/- 5.0 to 12.8 +/- 2.5 pmol CO2/min/mg; p less than 0.03) and distal mesenteric tyrosine hydroxylase activity was decreased 42% (from 7.73 +/- 1.2 to 4.46 +/- 0.8 pmol CO2/min/mg; p less than 0.03). In the 2K1C group, neither proximal nor distal mesenteric tyrosine hydroxylase activity was altered. Tyrosine hydroxylase activity was not detectable in the femoral arteries, or in the thoracic and abdominal aorta.(ABSTRACT TRUNCATED AT 250 WORDS)

[Enzymuria following administration of contrast media in hypertensive rats]

Renal complications may occur in risk patients with pre-existing kidney damage if x-ray contrast media are administered. Nothing is known of the exact mechanisms of these reactions. We examined in rats with long-term renovascular hypertension and resulting nephrosclerosis the low osmolar contrast media ioxaglate, iohexol and iopamidol in respect of their renal tolerance compared with an osmotically equivalent mannite solution. Under the conditions of intravenous pyelography, we observed directly after the administration of all substances (3.5 mg/kg body weight) an enhanced enzymuria of gamma-glutamyl transpeptidase and N-acetyl-beta-D-glucosaminidase. The loss of enzyme is mainly due to the osmotic effect of the preparations. The nonionic contrast media iohexol and iopamidol produce a slighter enzymuria than the ionic ioxaglate.

Detection and localization of renin messenger RNA in human pathologic tissues using in situ hybridization

In order to investigate the synthesis of renin in human pathologic tissues, the authors used in situ hybridization to detect and localize renin messenger RNA (mRNA). The probe was a 35S-radiolabeled 1.1-kb length complementary DNA of human renal renin. To compare the synthesis with the presence and the storage of renin, renin antigen was assessed by immunohistochemistry in the same tissues. The human pathologic tissues were as follows: two ischemic kidneys related to renovascular hypertension; two renal juxtaglomerular cell tumors; one extrarenal renin-secreting epithelioid sarcoma of soft tissues. In ischemic kidneys, the cells containing both renin mRNA and renin protein were found in numerous juxtaglomerular apparatus and in the wall of arterioles, shown by combined in situ hybridization and immunohistochemistry. Most of the tumor cells in the juxtaglomerular cell tumors and scarce tumor cells in the epithelioid sarcoma of soft tissues were positive by in situ hybridization and immunohistochemistry. These findings demonstrate that the presence of renin in these tissues is associated with local cellular production of renin. In particular, smooth muscle cells of the wall of arterioles are definitely capable of synthesizing renin. Moreover, in these tissues, gene expression (renin synthesis) and renin storage are concordant.

The vascular Na+-K+ pump in experimental hypertension

We assessed the role of putative circulating ouabainlike factor(s) on in vivo arteriolar function in rats with very early (less than 7 days; mean, 3 days) and chronic (greater than 4 weeks) benign, one-kidney, one clip (1K1C) hypertension. Thus, we measured vascular responses in vasodilated (nitroprusside or adenosine), vascularly isolated, innervated hindlimb vascular beds of chloralose-anesthetized 1K1C rats perfused with their own blood at 1 ml/min. Complete norepinephrine dose-response curves in 8 rats with chronic and 28 with early 1K1C hypertension, compared with appropriate normotensive control rats, showed unchanged thresholds and ED50 values. Magnitude of ouabain-induced leftward shifts of the norepinephrine dose-response curve in 18 rats with chronic and 21 with early 1K1C hypertension, compared with appropriate normotensive control rats, was unchanged. Blockade of neural uptake of norepinephrine by desimipramine (10(-7) M) in 8 1K1C rats did not alter these results. These findings provide no evidence in this form and these stages of hypertension that humoral ouabainlike inhibitors of the Na+-K+ pump evoke physiologically significant inotropic effects in arterioles in vivo. It is possible, however, that induction of vascular Na+-K+-adenosine triphosphatase by circulating inhibitors modified the vascular responses to norepinephrine and ouabain in these rats.

Measurement by bioluminescence technique of erythrocyte membrane Na+,K+-ATPase activity in hypertensive patients

Erythrocyte membrane Na+,K+-ATPase activity was measured using a bioluminescence technique in 28 hypertensive patients (24 with essential hypertension, 2 with renovascular hypertension and 2 with hypertension secondary to primary hyperaldosteronism) and in 28 normotensive control subjects matched for age and sex. Erythrocyte Na+,K+-ATPase activity was significantly reduced in the patients with essential hypertension (130.9 +/- 11.4 vs. 186.6 +/- 19.5 nmol ATP/mg prot per h; mean values +/- SEM; p less than 0.05) and in the patients with secondary hypertension. A significant negative correlation was found between erythrocyte Na+,K+-ATPase and systolic blood pressure (r = -0.603; p less than 0.01), but not between Na+,K+-ATPase and plasma renin activity or plasma aldosterone levels. These data confirm the findings of a number of previous studies reporting reduced activity of erythrocyte Na+,K+-ATPase possibly related to the presence of a circulatory inhibitor of sodium pump. The method, based on ATP assay by bioluminescence, presents a high degree of specificity as well as simple, rapid execution.

Intrarenal kallikrein-kinin activity in acute renovascular hypertension in dogs

The intrarenal kallikrein-kinin system was studied during the acute phase of renovascular hypertension induced by renal artery constriction and during teprotide inhibition of kininase II in the dog. Kallikrein-like activity measured by both kininogenase and esterolytic assays, was increased during renal artery constriction (p less than 0.5) and (p less than 0.01). The administration of teprotide resulted in a further increase of renal cortical kallikrein-like activity and inhibited kininase II activity (p less than 0.01). Following the inhibition of kininase II, the plasma concentration of kininogen was also significantly decreased (p less than 0.01). These results suggest that kininase II inhibition may increase levels of intrarenal and plasma kinins and that decreased degradation of kinin peptides may contribute significantly to the acute hypertensive effect of teprotide.

[Induction of blood plasma carboxycathepsin (angiotensin I-converting enzyme) in normo- and hypertensive rats in response to a single administration of captopril]

The experiments were carried out to elucidate the effect of carboxycathepsin (CC) activity inhibition by a specific inhibitor--captopril--on plasma enzyme concentration in normotensive rats and rats with renovascular hypertension. A single oral administration of captopril (10 mg/kg body weight) produced an increase in CC concentration in both hypertensive and sodium-depleted normotensive rats with a parallel decrease in arterial pressure, but had no effect on sodium-repleted normotensive rats. It is suggested that the increase in plasma CC concentration is a compensatory response to the inhibition of CC activity by captopril; it is also possible that the increase observed reflects the state of renin-angiotensin system.

Myocardial biochemical, contractile, and electrical performance after imposition of hypertension in young and old rats

The effects of renovascular hypertension on the biochemical, contractile, and electrical performance of myocardial tissue from rats of various ages has been examined. Male Fischer rats, 2, 7, 12, and 17 months old, were made hypertensive by constriction of the left renal artery. Ten weeks after the onset of hypertension, left ventricular papillary muscles were isolated from those four groups when 5, 10, 15, and 20 months old, respectively. Mechanical performance and transmembrane electrical events were recorded simultaneously. Contractile protein enzyme activity was determined in the same hearts from which papillary muscles were used for acquisition of mechanical and electrical information. There was a slight increase in blood pressure in control groups as a function of age while blood pressure maintained a range of approximately 179-188 mm Hg for all hypertensive groups. Heart weight of control animals increased significantly from 5 months to 20 months of age from 539 +/- 26 to 1088 +/- 56 mg, representing an increase of 101%. In hypertensive animals, heart weight increased 50% in 5-month-, 15% in 10-month-, 50% in 15-month-, and 11.7% in 20-month-old animals. Although control groups revealed alterations in mechanical, electrical, and biochemical parameters that increased as a function of age, the magnitude of the biochemical, contractile, and electrical response to hypertension varied monotonically with the extent of myocardial hypertrophy, rather than age per se. Adaptation to the stress of hypertension was observed in each age group, and was revealed as prolongation of mechanical and electrical timing parameters, depression of the load-velocity relation, and contractile protein enzyme activity. Thus, the stress of hypertension, which was tolerated by the 10- and 20-month-old animals with lesser relative hypertrophy and lesser changes in measured parameters, may represent a differential adaptation to the stress of hypertension.

Change in cortical active kallikrein during the onset of Goldblatt hypertension in the rat

In two-kidney, one clip hypertensive rats renal cortical kallikrein was studied one and two weeks following induction of the hypertension in comparison with sham time controls. Cortical active kallikrein was lower in hypertensive rats only at week 2, although blood pressure was significantly higher one week after clipping. Total cortical kallikrein was however never different in sham control and in hypertensive rats. This results provide evidence for a change in the activation of prekallikrein during the onset of Goldblatt hypertension.

Differing patterns of renal vein renin secretion in patients with renovascular hypertension, and their role in predicting the response to angioplasty

The correlation between the arteriographic appearance and functional significance of renal artery stenosis in hypertensive patients is poor. Measurements of renal vein renin in patients with unilateral renal artery stenosis undergoing renal angioplasty show that before angioplasty there is lateralization of renin secretion to the ischemic kidney, with suppression from the contralateral kidney. Following angioplasty this pattern returns to normal, with both kidneys showing similar increments of renin in the renal veins. The prediction of therapeutic outcome from renal vein renin measurements is more reliable (sensitivity 74%, specificity 100%) when expressed as the increment of renin for each renal vein over the inferior vena caval value than as the ratio between the two renal veins (sensitivity 62%, specificity 60%), but there is a high false-negative rate with both methods. Renal vein renin patterns cannot reliably distinguish between unilateral and bilateral renal artery stenosis, and in patients with bilateral stenoses tend to show lateralization to the more ischemic kidney.

Factors affecting renal vein renin ratio in renal artery stenosis. Secretion of inactive renin

All four factors which theoretically may affect the renal vein renin ratio in unilateral renal artery stenosis--increased renin secretion and diminished renal plasma flow on the stenotic side; suppressed renin secretion and renin extraction on the contralateral side--have been assessed. In a series of patients with unilateral renal artery stenosis, the renal vein ratio of active renin was more closely related to the reduction of renal plasma flow than to renin secretion rate on the affected side. On the contralateral side renin secretion was suppressed while angiotensin II was extracted. During long-term treatment with the converting enzyme inhibitor enalapril, peripheral plasma angiotensin II was lowered, while active renin concentration was markedly elevated, both in arterial plasma and in renal venous plasma of the stenotic kidney; the contralateral kidney became a net extractor of active renin. Thus, all 4 factors which theoretically affect the renal vein renin ratio can operate clinically. Both before and during enalapril, the affected kidney secreted inactive renin.

Urinary kallikrein activity in pregnant hypertensive rats

Goldblatt one-kidney one-clip (G1K-1C) hypertensive rats were studied to determine the changes of blood pressure (BP) and urinary kallikrein (UK) excretion throughout pregnancy. Uninephrectomized rats (Unx) were used as controls. Both groups showed a significant decrease in BP on day 21 of pregnancy, although G1K-1C rats had higher values. UK activity was markedly stimulated in both groups, reaching its highest level on day 21. This increment in UK was due to greater delivery and/or synthesis of the enzyme, since no change was observed in the active fraction. We postulate that the highly activated kallikrein-kinin system might be contributing to the hypotensive effect of pregnancy.

Unstimulated renal venous renin ratio predicts improvement in hypertension following nephrectomy for unilateral renal disease

The ability of renal venous renin ratio (RVRR) to predict the blood pressure response to nephrectomy was studied in 45 hypertensive patients followed for at least 1 year after nephrectomy. Twenty patients had unilateral chronic parenchymal renal disease (UCPR) and 25 patients had unilateral renal artery stenosis (RAS). The RVRR procedure was performed according to a strict protocol which included sodium restricted diet (40 mmol daily) and hospital admission, with one set of unstimulated samples collected after overnight recumbency, and at least one further set collected after sympathetic nervous system stimulation induced by tilting or i.v. diazoxide. In only 3 of 12 patients with serum creatinine 0.15 mmol/l or higher and presumed bilateral renal disease was hypertension improved. If these 12 patients are excluded, RVRR was a good predictor of outcome, but only if the question of unstimulated and stimulated ratios was considered. Whereas inclusion of stimulated ratios increased the predictive accuracy to 81% in RAS, and avoided two false-negatives, in UCPR the stimulated ratio created four false-positives. Since there were no false-negatives and six true-negatives in UCPR, overnight recumbent RVRR was a perfect predictor of outcome in this sub-group. It appears that RVRR without sympathetic stimulation is most reliable in UCPR, and RVRR during sympathetic stimulation in RAS, raising the question that renin regulation may be different in these two conditions.

Renovascular hypertension. Ability to renal vein ratio to predict the blood pressure level 18-24 months after surgery

Fourteen patients with severe hypertension and renal artery stenosis were treated surgically. One patient died 4 days after surgery due to a cerebral thrombosis. The other 13 patients were followed for 18-24 months. Five were considered cured since the diastolic blood pressure (DBP) was less than or equal to 90 mm Hg without therapy. Five were improved since DBP was less than or equal to 100 mm Hg during treatment with only one or two antihypertensive agents. There were unchanged. Renal vein renin ratio (RVRR) was greater than or equal to 1.5 either before or after furosemide in all patients who were cured or improved and less than or equal to 1.5 in 2 of 3 who were unchanged. It can be concluded that surgical treatment cured or improved 77% of the patients, and that a RVRR greater than or equal to 1.5 is a good predictor of the blood pressure lowering effect of surgery.

Renal venous renin determinations in renovascular hypertension. Diagnostic and prognostic value in unilateral renal artery stenosis treated by surgery or percutaneous transluminal angioplasty

To assess the diagnostic and prognostic value of renal venous renin levels in renovascular hypertension, 95 patients with severe unilateral renal artery stenosis were studied. Surgery (n = 52) or percutaneous transluminal dilation (n = 43) were done irrespective of renal venous renin levels. Lateralization of renin secretion as assessed by the PRA ratio and the renin secretion index was found in the majority of patients (66% and 88%, respectively). Patients with fibromuscular hyperplasia had more frequently PRA ratios less than 1.5 than those with arteriosclerotic stenosis (p less than 0.05). The renin secretion index proved to have a higher sensitivity (92%) and predictive value (92%) for a successful outcome of both surgery and PTA than the PRA ratio (69% and 89%, respectively), while the specificity was the same with both parameters (42% and 43%, respectively). The contralateral suppression index was most specific in predicting an unfavorable outcome. However, with all ratios used, a considerable number of false-negative and false-positive tests were observed both with surgery and PTA, a finding limiting the value of the method in selecting patients for these interventions. Other factors, such as age of the patient, kidney function and the underlying arterial disease turned out to be equally important prognostic factors. Thus, although cure after both surgery and PTA is more likely in the presence of lateralized renin secretion and contralateral suppression, the method does not allow to exclude patients with severe renal artery stenosis, hypertension and negative renal venous renin tests from these interventions.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal vein renin in renovascular hypertension: the experience of two Italian centers

A retrospective analysis of renal vein renin results has been done in 96 patients with renal artery stenosis and hypertension studied in two Italian centers (Sassari and Pisa) with respect to the outcome of either surgery or percutaneous transluminal angioplasty (PTA). In all patients the renal vein renin ratio and the V-A/A ratios for the affected and unaffected kidney were calculated. Each patient underwent surgery (75) of PTA (21): 71 subjects were cured, 17 improved whereas the arterial pressure did not vary after revascularisation procedure in 8 patients. In the Pisa series all 54 patients showed a lateralisation with contralateral renin suppression and 95% of them benefitted from surgery. In the Sassari series 42 patients were submitted to PTA or surgery, not only on the basis of a positive renal vein renin study but taking into account a complete clinical evaluation: 8 of them were cured or improved in spite of negative renal vein renin criteria. In the two series, the better predictive index appeared to be the suppression of the renin secretion from the contralateral kidney while the high/low renin ratio showed a consistent amount of false-positive and false-negative results. Our retrospective study demonstrates that the renal vein test in hypertensive patients with renal artery stenosis is highly predictive of the curability of the disease, particularly when contralateral suppression of renin secretion is present. On the other hand, since patients with negative renin indexes can also take benefit from surgery of PTA, the renin parameters cannot be adopted as the sole criterion in making the decision to operate.

Kallikrein-kinin system in severe experimental hypertension

Plasma levels of low and high molecular weight kininogens, prokallikrein and active kallikrein were determined in four models of experimental hypertension and in genetically hypertensive rats. The high molecular weight kininogen remained essentially unaltered in all groups, whereas the low molecular weight kininogen was decreased in the renovascular groups. In the glucocorticoid hypertensive rats low molecular weight kininogen increased, but rats with hypertension induced both by renovascular and glucocorticoid mechanisms had normal kininogen. Genetically hypertensive rats had levels of low molecular weight kininogen similar to the ones observed in control group. The data presented reinforce the hypothesis of a participation of the kallikrein-kinin system in the etiopathogenesis of hypertension, indicating an implication of the low molecular weight kininogen in some types of severe experimental hypertension.