Influence of gender and family history of hypertension on autonomic control of heart rate, diastolic function and brain natriuretic peptide.

OBJECTIVE: To verify in a unitary view whether autonomic control of heart rate and cardiac structure and function are modified early in offspring of hypertensive families. METHODS AND RESULTS: We selected 87 age- and sex-matched young normotensive subjects with (n = 45) and without (n = 42) a family history of hypertension who underwent evaluations of arterial pressure, time-domain parameters of autonomic heart rate control (24-h ECG monitoring), spectral baroreflex sensitivity, left ventricular geometry and function (echo-Doppler) and plasma brain natriuretic peptide levels (BNP). The group with a family history of hypertension significantly differed from their counterparts for systolic pressure (119 +/- 11 versus 114 +/- 9 mmHg, P< 0.05), heart rate (RR interval, 766 +/- 64 versus 810 +/- 93 ms, P< 0.05), heart rate variability [the standard deviation of normal RR intervals (SDNN), 147 +/- 29 versus 171 +/- 33 ms, P < 0.051, diastolic function (isovolumetric relaxation time, 65 +/- 9 versus 60 +/- 8 ms, P< 0.05) and BNP (23 +/- 13 versus 37 +/- 10 pg/ml, P< 0.05). Baroreflex sensitivity values did not differ between the two groups. When gender was considered, all the above-mentioned measures, as well as baroreflex sensitivity, were significantly different between males with and without a family history of hypertension but not between females, except for BNP, which was lower in males and females with a history of hypertension (males, 24 +/- 11 versus 38 +/- 8 pg/ml, P< 0.01; females 21 +/- 14 versus 36 +/- 13 pg/ml, P < 0.05). CONCLUSIONS: Male, but not female, hypertensive offspring have modified diastolic function and autonomic control of heart rate; BNP is the only parameter able to characterize hypertensive offspring independently from the influence of gender. This provides the hypothesis that the impaired production of this hormone could play a primary role in the pre-hypertensive state.

Endothelin-1-receptor-mediated responses in resistance vessels of young and adult spontaneously hypertensive rats.

OBJECTIVE: To assess whether primary changes in endothelin-1 (ET-1) receptor responsiveness or secondary vessel functional modifications could characterize the effects evoked by ET-1 in the mesenteric vascular bed (MVB) of prehypertensive 5-week-old and 12-week-old spontaneously hypertensive rats (SHRs). DESIGN AND METHODS: We used male 5-week-old and 12-week-old SHRs and sex- and age-matched Wistar-Kyoto (WKY) rats as controls. ET-1 receptor responsiveness was evaluated by ET-1 (0.04-2 micromol/l) concentration-response curves and repeated with indomethacin and BQ-123 (0.1-0.5 micromol/l), the latter a selective ETA receptor antagonist. ETB receptor responsiveness was tested by sarafotoxin S6c (1-100 nmol/l) and IRL-1620 (0.1-10 nmol/l) concentration-response curves, obtained in the noradrenaline-precontracted MVB. RESULTS: At 5 weeks of age, ET-1 induced a similar concentration-dependent contraction in SHRs and WKY rats, with an overlapping BQ-123 pA2 value (negative common logarithm of the antagonist that produces an agonist dose ratio of 2) in the two strains. Indomethacin was ineffective in both groups. Sarafotoxin S6c and IRL-1620 both evoked an ETB-mediated, significant relaxation, only in WKY rats. In 12-week-old SHRs, ET-1 evoked a markedly increased maximal effect compared with the response in WKY rats (P< 0.01); this was prevented by treatment with indomethacin. The BQ-123 pA2 value was higher in SHRs than in WKY rats (P< 0.01). Both sarafotoxin S6c and IRL-1620 evoked a significant concentration-dependent relaxation in WKY rats, which was not detected in SHR preparations. CONCLUSIONS: Our results could suggest that the different responses evoked by ET-1 in the MVB of SHRs during the onset of hypertension may be related partially to primary alterations in the ET-1 receptorial pattern and partially to the onset of high blood pressure, leading to an impairment in the haemodynamic balance.

Abnormal transport of inorganic phosphate in left ventricular mitochondria from spontaneously hypertensive rats.

INTRODUCTION: The aim of this study was to investigate the kinetic properties of inorganic phosphate (Pi) translocator in intact mitochondria isolated from the hypertrophied left ventricular tissue of spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) at the ages of 5 and 24 weeks, before and after the development of hypertension. METHODS: The dependence of the Pi uptake rate on substrate concentration was measured in both absence and presence of mersalyl by spectroscopic techniques. RESULTS: Saturation characteristics were found (Km 250.0 +/- 25.0 and 15.0 +/- 1.5 microM for 5- and 24-week-old SHR, and 300.0 +/- 30.0 and 40.0 +/- 4.5 microM for WKY rat mitochondria, respectively, p < 0.05; Vmax 1.2 +/- 0.16 and 0.1 +/- 0.01 delta A/min x mg mitochondrial proteins for 5- and 24-week-old SHR, and 4.1 +/- 0.39 and 1.4 +/- 0.12 delta A/min x mg mitochondrial proteins for 5- and 24-week-old WKY rats, respectively, p < 0.05). When Pi carrier activity was measured using concentrations which are assumed to be in the cytosol under physiological conditions, Pi carrier velocity was 1.1 and 0.1 in SHR and 4.6 and 1.4 delta A/min x mg mitochondrial proteins in WKY, at 5 and 24 weeks, respectively. CONCLUSIONS: The significant decrease in the activity of the Pi carrier could imply that pressure overload is critical in SHR. Nevertheless, as decreased activity was found in SHR also at an early age when animals do not show stable increased blood pressure levels, we suggest that other factors might contribute to the abnormalities of Pi transport in mitochondria. An altered gene expression possibly related to a primary defect in this strain or, alternatively, to an abnormal regulation of protein synthesis might be proposed as additional factors affecting Pi carrier activity. The results of this study, together with previous data of the literature showing abnormalities in energy production mechanisms, allow us to hypothesize a profound rearrangement of energy metabolism at the mitochondrial level in this model of left ventricular hypertrophy and hypertension.

Extracellular matrix gene expression in the left ventricular tissue of spontaneously hypertensive rats.

The aim of this study was to investigate the extracellular matrix gene expression in the hypertrophied left ventricular tissue of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats, at early and mature ages. Interestingly, with age, a marked increase (+85% and +187% at 25 and 30 weeks of age, respectively, p < 0.01, vs 5 weeks) in matrix metalloproteinase-1 (MMP-1) mRNA levels in SHR and a progressive decrease (-50%, -70%, -78%, -70% at 10, 15, 25 and 30 weeks, respectively, p < 0.01, vs 5 weeks) in WKY were seen. Moreover, mRNA levels were significantly lower in SHR at 5 weeks. The analysis of mRNA expression for the tissue inhibitor of metalloproteinase-1 (TIMP-1) showed a significant increase in WKY (+44% and +44%, vs 15 and 25 weeks, respectively, p < 0.05), whereas there were no significant changes in SHR with development. At 30 weeks TIMP-1 mRNA levels were significantly reduced in SHR. Temporal trends of procollagen alpha1(I) and procollagen alpha1(III) mRNA levels were similar in both strains, but lower levels for procollagen alpha1(III) were found in SHR at 5 and 30 weeks. Although no significant differences were measured between the strains, mRNA levels for fibronectin were found decreased in WKY and increased in SHR with age. The results of the present study suggest an altered balance between collagen deposition and collagen degradation with development in this model of left ventricular hypertrophy and hypertension.

Functional characterization of endothelin receptors in hypertensive resistance vessels.

OBJECTIVE: The physiological and pathophysiological functions of endothelin-1 in modulating the regional blood flow of normal and spontaneously hypertensive rats (SHR) were studied in the perfused mesenteric vascular bed, a useful model for investigating resistance vessels. DESIGN AND METHODS: We used 12-week-old SHR and Wistar-Kyoto (WKY) rats. Endothelin A (ETA) receptor responsiveness was evaluated by endothelin-1 (0.2-2 mumol/l) concentration-response curves, and repeated in the presence of indomethacin and the ETA and endothelin B (ETB) receptor antagonists BQ-485 and BQ-788, respectively. ETB receptor responsiveness was tested by sarafotoxin S6c concentration-response curves, obtained in the noradrenaline-precontracted mesenteric vascular bed, and repeated after treatment with BQ-788 and after endothelial denudation. RESULTS: In both groups, endothelin-1 induced concentration-dependent contraction; SHR exhibited a markedly increased maximal effect compared with WKY rats (P < 0.01). BQ-485 produced a shift to the right for endothelin-1 concentration-response curves in both groups, with a higher pA2 (negative common logarithm of the antagonist that produces an agonist dose ratio of 2) value in SHR than in WKY rats (P < 0.01). The increase in the maximal effect produced by endothelin-1 in SHR was prevented by indomethacin, which also induced a significant increase in the endothelin-1 concentration producing the half-maximal response (EC50) in SHR (P < 0.05). Sarafotoxin S6c produced an ETB-dependent endothelium-mediated relaxant effect in WKY rats, which was not observed in SHR. CONCLUSIONS: The higher vasoconstriction induced by endothelin-1 in SHR may be related to a greater number of available ETA receptors, due to the presence of an ETA receptor subtype. This mechanism may be linked to the production of prostanoids that add to the direct endothelin-1-evoked vasoconstriction. These results, together with the lack of relaxation in response to sarafotoxin S6c in SHR, suggest that an imbalance in the endothelin-1 ability to induce both contraction and relaxation is present in SHR with sustained hypertension, manifesting as a greater contractile effect evoked in this strain.

Endothelin, microcirculation and hemorheology.

Although a large amount of data concerning microcirculation and cardiovascular disease exists, little is known about microcirculation and hypertension. This is largely due to the difficulty in selectively examining capillaries and metarterioles, independently from small arteries or large vessels. The physiological role of capillaries and metarterioles, the two elements that make up the microcycle, is peculiar and closely related to metabolic exchange. During the hypertensive state, several factors can alter these mechanisms. These include elevated plasma viscosity, abnormal membrane properties of red blood cells, and an increase in fibrinogen, LTL and hematocrit levels. The question of whether an abnormal release of endothelium derived vasoactive factors from capillaries, or an abnormal production of chemical factors by blood cells running through the vasculature area is present in hypertensives is fascinating, but unfortunately neither experimental nor clinical data has yet been able to answer it. Recently, evidence of the formation of endothelin by red blood cells from endogenous precursors was given, suggesting that red blood cells may modulate the vascular tone both directly, through the release of ATP or endothelin-1, and indirectly, when hemolysis occurs and hemoglobin is released. The pathological significance of these findings has not been clearly demonstrated in hypertension thus far, although it is reasonable to hypothesise that there are clinical implications for the pathogenesis and the progression of vascular damage during the hypertensive state.

ATP synthesis and export in heart left ventricle mitochondria from spontaneously hypertensive rat.

Use was made of mitochondria isolated from heart left ventricles of either spontaneously hypertensive or age-matched Wistar-Kyoto rats used as a control to find out whether hypertrophy (5-week-old rats) or hypertrophy/hypertension (24-week-old rats) can cause change in the mechanisms by which ATP is synthesised via ATP synthase and subsequently exported via the ADP/ATP translocator outside mitochondria. To do this, photometric measurements were made of the rate of ATP appearance in the extramitochondrial phase, which occurs as a result of ADP addition to mitochondria. In mitochondria from spontaneously hypertensive rats deficit of ATP production was found dependent on changes in the KmADP and Vmax values of both the ADP/ATP translocator and the ATP synthase. The ADP/ATP translocator was found to determine the rate of ATP production outside mitochondria in all the tested samples. In an initial investigation carried out to ascertain how cell ATP deficit can be counterbalanced, an increase in both adenylate kinase and creatine kinase activities was found in both hypertrophy and hypertrophy/hypertension. A possible increase in anaerobic glycolysis was also suggested by the increased lactate dehydrogenase activity.

L-type calcium channels modulate the regression of left ventricular hypertrophy after ace-inhibition in genetic hypertension.

The aim of this study was to investigate the possible link between the regression of the left ventricular mass induced by ACE-inhibition and L-type calcium channels. For this purpose, an evaluation of both L-type calcium channels and AT1 receptor patterns in the left ventricular tissue of adult spontaneously hypertensive rats (SHR) was made before and after long-term treatment with ramipril. An abnormal density of both dihydropyridine and AT1 receptors was observed in SHR at 24 weeks, compared to age-matched control Wistar-Kyoto (WKY) rats (dihydropyridine receptor Bmax: 1. 30+/-0.09 vs 1.14+/-0.06 pmol mg-1 proteins, P<0.001; AT1 receptor Bmax: 1.35+/-0.07 vs 2.62+/-0.08, P<0.001 pmol mg-1 proteins). A treatment for 10 weeks with ramipril induced a significant decrease in the left ventricular mass index of SHR, as well as a significant decrease in dihydropyridine receptor density (Bmax: 0.96+/-0.01 vs 1. 39+/-0.08 pmol mg-1 proteins, P<0.001) and a significant increase in AT1 receptor density (Bmax: 3.08+/-0.26 vs 2.78+/-0.09 pmol mg-1 proteins, ramipril-treated SHR vs vehicle-treated SHR, P<0.001). These results suggest that the decrease in left ventricular mass after treatment with ramipril may be dependent on changes in L-type calcium channels other than the direct effect on circulating and tissue angiotensin II (ang II) levels: involvement of calcium channels and subsequent calcium influx into cardiac cells could be proposed as an additional mechanism for the regression of left ventricular mass after ACE-inhibition.

Mitochondrial energy metabolism in the left ventricular tissue of spontaneously hypertensive rats: abnormalities in both adeninenucleotide and phosphate translocators and enzyme adenylate-kinase and creatine-phosphokinase activities.

The aim of this study was to investigate the oxidative phosphorylation and additional adenosinetriphosphate (ATP) production mechanisms in mitochondria isolated from hypertrophied left ventricles of spontaneously hypertensive rats (SHR). Measurements of adenosinediphosphate (ADP)/ ATP and inorganic phosphate (Pi) carrier activities showed a significant reduction of Vmax values thus suggesting a general decrease of ATP supply in the hypertrophied ventricles. Investigation of mitochondrial enzyme activities showed 45% and 90% increases of adenylate-kinase and 80% and 110% increases of creatine-phosphokinase in 5- and 24-week-old SHR, before and after the development of the hypertensive state, respectively. The abnormalities found in SHR at the mitochondrial level suggest a profound rearrangement of energy production mechanisms in this model of left ventricular hypertrophy; whether the defects are determined genetically, and then worsen with the hypertensive state, remains to be determined.

Carrier-mediated transport controls hydroxyproline catabolism in heart mitochondria from spontaneously hypertensive rat.

In this study we have investigated hydroxyproline transport in rat heart mitochondria and, in particular, in heart left ventricle mitochondria isolated from both spontaneously hypertensive and Wistar-Kyoto rats. Hydroxyproline uptake by mitochondria, where its catabolism takes place, occurs via a carrier-mediated process as demonstrated by the occurrence of both saturation kinetics and the inhibition shown by phenylsuccinate and the thiol reagent mersalyl. In any case, hydroxyproline transport was found to limit the rate of mitochondrial hydroxyproline catabolism. A significant change in Vmax and Km values was found in mitochondria from hypertensive/hypertrophied rats in which the Km value decreases and the Vmax value increases with respect to normotensive rats, thus accounting for the increase of hydroxyproline metabolism due to its increased concentration in a hypertrophic/hypertensive state.

[Aging and isomyosin pattern of the left ventricle in spontaneously hypertensive and Wistar Kyoto rats]. / Invecchiamento e pattern isomiosinico del ventricolo sinistro di ratti spontaneamente ipertesi e Wistar Kyoto.

Changes of the contractile proteins in the left ventricle from spontaneously hypertensive rats (SHR) are extensively documented with the development of the hypertensive state and with ageing. This study was undertaken to determine whether also the left ventricle from normotensive rats exhibits age-related changes of the myosin pattern. The relative distribution of myosin isoforms was investigated in Wistar Kyoto (WKY, n = 50) and SHR (n = 50), both at the 5th, 9th, 24th, 48th and the 72nd week of life. A significant decrease in V1 as well as an increase in V3 percentage values, compared to the data obtained at the 5th week were observed in SHR from the 9th week, concomitantly to the rise in blood pressure values. These changes were more consistent with ageing (5 weeks: V1 99.0 +/- 0.9%, V2 0.6 +/- 0.1%, V3 0.4 +/- 0.3%; 72 weeks: V1 5.3 +/- 3.9%, V2 3.0 +/- 2.7%, V3 91.7 +/- 9.7%). In WKY rats, a significant decrease in V1 percentage values was detected at the 24th week and it was evident till the 72nd week. V3 significantly changed only at the 48th and the 72nd week (5 weeks: V1 100.0 +/- 0.0%; 72 weeks: V1: 41.4 +/- 6.5%, V2 13.3 +/- 2.8%, V3 45.5 +/- 6.9%). The results of this study confirm that alterations in the left ventricle isomyosin pattern occur early in SHR with the rise in blood pressure values and the increase in left ventricular mass. In contrast, modifications in the myosin isoform distribution were found only in WKY with ageing. These findings may be related to the biochemical changes occurring in the myocardial tissue either gradually, during the advanced ages of life, or early due to the hypertensive state.

Changes in enzyme levels in hypertensive heart tissue.

The levels of activity of some enzymes involved in oxidative metabolism have been determined in left ventricular tissue from spontaneously hypertensive rats compared with those in normotensive controls. Levels of pyruvate kinase were increased about 1.3 fold indicative of elevated glycolytic activity. Similarly, enhanced levels of lactate dehydrogenase were found, consistent with a requirement for increased oxidation of cytosolically-generated NADH. In addition a more active malate-aspartate shuttle, which in heart provides the major route for transfer of reducing equivalents to the mitochondria, was suggested by elevated levels of the cytosolic isoenzyme of aspartate aminotransferase; malate dehydrogenase did not increase but the activity of this enzyme is very high and unlikely to be rate-limiting in the shuttle. The levels of expression of mRNAs for three of these enzymes (pyruvate kinase, aspartate aminotransferase and malate dehydrogenase) were also determined and correlated well with the extent of change, if any, in the changes in enzymatic activity. Thus it seems that one response to development of hypertension in rats is an increase in expression of the genes for certain key enzymes involved in oxidative metabolism.

Left ventricular hypertrophy in spontaneously hypertensive rat: effects of ACE-inhibition on myocardiocyte ultrastructure.

The aim of this study is to investigate the effects of two ACE-inhibitors with different chemical formulae, cilazapril (CLZ) and captopril (CPT), on left ventricular myocardiocytes from spontaneously hypertensive rats (SHR), characterized by ultrastructural alterations associated with left ventricular hypertrophy, and from Wistar-Kyoto (WKY) rats, considered as controls. After CLZ-treatment, not remarkable changes are observed in WKY myocardiocytes, whereas SHR ones show a considerable reduction in their original alterations in ultrastructure. After CPT-treatment, both SHR and WKY myocardiocytes are altered in ultrastructure. The morphometric investigation confirms that CPT and CLZ produce different effects. Even if the drugs induce a similar decrease in blood pressure and left ventricular mass index, CLZ unlike CPT seems to improve the ultrastructural abnormalities associated with left ventricular hypertrophy. These changes could be related to the different chemical structure of CLZ and CPT, or to a different affinity of the two drugs for the local renin-angiotensin system.

[Clinical experience with alpha blockers and calcium antagonists in the perioperative treatment of pheochromocytoma]. / Esperienza clinica con alpha-bloccanti e calcioantagonisti nel trattamento perioperatorio del feocromocitoma.

This study aims to value the efficacy of the association between alpha-blockers and calcium channel-blockers, administered per os, in the reduction of preoperative preparation in patients with phaeochromocytoma and the calcium channel-blockers utility when are administered e.v. in the control of development of arterial paroxysmal hypertension during surgical manipulations. The trial had been conducted on 5 patients which have undergone the operation, before the operation we administered per os nifedipine and phonoxybenzamine for 8 days and during the operation we administered diltiazem e.v. The association between alpha-blockers and calcium-blockers per os, has reduced the preparation stage and has controlled the pressure parameters during the preoperative treatment. When we utilized diltiazem during the operation, we haven't note a good hemodynamic stability; these results are opposed to Tokioka's. Calcium channel-blockers and alpha-blockers seem to be a good therapy in the preoperative preparation of patients with phaeochromocytomas and they seem to be able to take fastly the standard of preoperative preparation.

Non-invasive haemodynamic study in hypertensive subjects after treatment with verapamil slow release.

Aim of this study is to investigate the haemodynamic effects, after the short and long-term antihypertensive treatment. After a wash-out period and a placebo treatment period, 30 hypertensive patients received verapamil SR (slow release, 240 mg o.d.) for 30 days. A significant decrease in systolic and diastolic blood pressure was obtained already 4 h after the first administration of verapamil; it was more evident and persistent throughout the study. No significant changes of heart rate or PR interval in ECG were observed. A significant decrease in total vascular resistances, both supine and upright, was evident already 4 h after the drug intake and observed throughout the study. The major effect was obtained after one month. No significant changes of cardiac output, cardiac index and stroke volume were recorded. Furthermore, plasma verapamil levels were measured to confirm that the haemodynamic effects are obtained by low drug concentrations. The present study provides evidence that the antihypertensive effect of verapamil, whose mechanism is the reduction of total vascular resistances, is progressive, long acting and achieved by low plasma levels, when slow release formulation is considered.

Decrease of phagocytic functions in hypertensive rats.

The present investigation was aimed to examine non-specific immunologic capabilities of spontaneously hypertensive rats (SHR) during the development of hypertension. In vitro phagocytosis and oxidative killing exerted by monocytes, polymorphonuclear cells (PMN) and splenic macrophages (SpM0) were evaluated in SHR at 5-, 8-, and 24-weeks of age. Age-matched normotensive Wistar-Kyoto (WKY) rats were used as controls. Results showed that in pre-hypertensive stage (5-wk) there was no difference between SHR and WKY rats with regard to non-specific immunologic functions. Statistically significant differences in both phagocytosis and oxidative killing arose in early hypertensive stage (8-wk) and became more marked in adult SHR with established hypertension (24-wk). In conclusion, our data provide evidence of novel immunologic abnormalities in SHR in terms of ingestion and bactericidal phagocytic capabilities. The mechanisms responsible for these impaired immunologic functions may depend on various suppressive factors which will be object of discussion.

Left-ventricular hypertrophy in the spontaneously hypertensive rat: effect of ACE inhibitors on ultrastructural morphology.

The ACE inhibitors cilazapril and captopril were administered at 10 and 100 mg/day, respectively, to spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto rats (WKY) from the 12th to the 22nd week of life. Both drugs produced statistically significant reductions in systolic and diastolic blood pressure, left-ventricular mass and index of left-ventricular hypertrophy in SHR. After cilazapril treatment, the morphology of SHR cardiocytes became similar to that in untreated normotensive rats, while in captopril-treated rats, myofibrils were disarranged, obliquely oriented and smaller than normal, with areas of electron-transparent sarcoplasm separating the myofibril bundles; mitochondria were also altered. In WKY rats, we observed no statistically significant changes in blood pressure, ventricular weight and hypertrophy index between the two drugs; however, there were different effects of the two drugs on the ultrastructural morphology of the myocardium. These observations suggest that these two molecularly dissimilar ACE inhibitors act differently at the tissue level despite similar effects on blood pressure and left-ventricular mass.