Serum collagen markers and heart failure.

Increased myocardial collagen accumulation is present in almost every cardiac disease and plays an important role in the reduced heart function. N-terminal and C-terminal propeptides of collagen type I and III, the two major collagen types in the heart, can be assayed in serum.These propeptides (PINP, PIIINP, PICP, ICTP) reflect collagen synthesis and degradation. The use of these serum collagen biomarkers as prognostic or diagnostic tools is an area of active investigation. In this review article these studies will be discussed as well as the limitations of these serum biomarkers as indicators of cardiac fibrosis.

Arginine-aminopeptidase in rat cardiac fibroblastic cells participates in angiotensin peptide turnover.

OBJECTIVE: The aim of the present study was to elucidate the presence in rat cardiac fibroblastic cells of arginine-aminopeptidase and its involvement in the hydrolysis of angiotensin peptides. METHODS: Peptidase activity was measured as hydrolysis of the synthetic substrates, aryl-p-nitroanilides. Immunoblottings were performed with antibodies to aminopeptidase B and Glyceraldehyde-3-phosphate dehydrogenase. RESULTS: Arginine-aminopeptidase found in cardiac fibroblasts (Fb) was arginine and lysine specific, sensitive to various aminopeptidase (AP) inhibitors and to the inhibitor of metalloproteases, 1.10-phenatroline. Experiments with arphamenine A, a specific inhibitor of aminopeptidase B, have shown the presence of two Arginine-aminopeptidase activities: arphamenine-sensitive: chloride-stimulated Arginine-aminopeptidase, and arphamenine-insensitive: chloride-insensitive Arginine-aminopeptidase. Transforming growth factor-beta1 stimulated both Arginine-aminopeptidase activities by approximately threefold. Immunoblot with an antibody specific to rat aminopeptidase B has revealed that arphamenine-sensitive: chloride stimulated aminopeptidase is aminopeptidase B. Arginine-p-nitroanilide hydrolysis was significantly inhibited by angiotensin peptides such as angiotensin (1-10), (1-8), (1-7), (1-4), (5-8), (4-8), (3-8), and (2-8) at the concentration of 50 micromol/l which was fourfold less than the Arginine-p-nitroanilide concentration. CONCLUSIONS: Our data show that chloride-insensitive Arginine-aminopeptidase could contribute to the hydrolysis of all studied angiotensin peptides in concert with other peptidases present in fibroblasts. Some of the peptides could probably not be hydrolyzed by Arginine-aminopeptidase. Instead, they could be first hydrolyzed by another peptidase in fibroblasts and the product of this hydrolysis could be a substrate for Arginine-aminopeptidase. The data obtained suggest that Arginine-aminopeptidase could perform processing of angiotensin peptides in the myocardium and participate in processes regulated by angiotensins such as fibrosis.

Role of intracardiac renin-angiotensin-aldosterone system in extracellular matrix remodeling.

Functional angiotensin II receptors have been documented in cardiac fibroblasts as well as an intracardiac aldosterone system that responds to short- and long-term physiological stimuli. In vitro, angiotensin II increased cardiac fibroblast-mediated collagen synthesis and mRNA levels of collagen type I, type III, pro-alpha1 (I) collagen, pro-alpha1 (III) collagen and fibronectin, and inhibited matrix metalloproteinase I activity. The angiotensin II-stimulated secretion and expression of collagen was completely abolished by AT1 receptor antagonism, but not affected by AT2 receptor antagonism. In vivo, chronic infusion of angiotensin II increased the collagen volume fraction in the ventricles. Angiotensin-converting enzyme (ACE) inhibition and AT1 receptor antagonism, but not AT2 receptor antagonism, reduced collagen deposition in the myocardium in spontaneously hypertensive rats and in rat myocardium following myocardial infarction. During chronic aldosterone infusion in uninephrectomized rats on a high-salt diet, a marked accumulation of interstitial and to a lesser extent perivascular collagen occurs in the heart in both ventricles. The cardiac fibrosis in this aldosterone model is prevented by spironolactone. During the continuous infusion of aldosterone in the rat, the appearance of fibrosis was delayed and started 4 weeks after the beginning of the infusion, which argues against a direct effect of aldosterone. The mechanism of aldosterone-salt-induced cardiac fibrosis possibly involves angiotensin II acting through upregulated AT1 receptors and the cardiac AT1 receptor is the target for aldosterone. An accumulation of collagen in the heart has also been found in patients with adrenal adenomas and during chronic activation of the renin-angiotensin-aldosterone system such as in surgically-induced unilateral renal ischemia, unilateral renal artery banding or renovascular hypertension. Spironolactone prevents aortic collagen accumulation in spontaneously hypertensive rats. In patients with stable chronic heart failure, spironolactone treatment in addition to diuretics and ACE inhibition reduced circulating levels of procollagen type III N-terminal aminopeptide. Also, in the Randomized Aldactone Evaluation Study, spironolactone coadministered with conventional therapy of ACE inhibitors, loop diuretics and digitalis in patients with symptomatic heart failure defined as NYHA classes III-IV, reduced total mortality by 30%.

T-lymphocyte and plasma angiotensin-converting enzyme activity during enalapril and losartan administration in humans.

This study evaluated the long-term effects of the angiotensin-converting enzyme inhibitor enalapril and the angiotensin II type 1 receptor antagonist losartan on the angiotensin-converting enzyme activity in T lymphocytes and plasma in patients with essential hypertension. The study was a randomized, placebo-controlled, double-blind, crossover design. Nine patients with sitting blood pressure > or = 95 mm Hg and < or = 105 mm Hg at the end of a 4-week placebo run-in period entered the double-blind phase of the study, which consisted of three 6-week periods during which patients were treated with placebo, enalapril (20 mg, once daily), or losartan (50 mg, once daily) The angiotensin-converting enzyme activity in T lymphocytes was measured as the activity of the degradation of the substrate Hippuryl-His-Leu and as the appearance of the dipeptide His-Leu, which was quantified spectrofluorometrically. Enalapril but not losartan suppressed (p < or = 0.01) the angiotensin-converting enzyme activity in plasma, whereas it stimulated (p < or = 0.05) the angiotensin-converting enzyme activity in circulating T lymphocytes. Our data document induction of angiotensin-converting enzyme in human T lymphocytes during long-term treatment with the angiotensin-converting enzyme inhibitor enalapril. Angiotensin II receptor type 1 antagonism with losartan had no effect on plasma or lymphocytic angiotensin-converting enzyme.

Long-term treatment with enalapril or losartan does not show antiproliferative effects in peripheral blood mononuclear cells.

The objective of this study was to evaluate the long-term effects of enalapril, an angiotensin-converting enzyme inhibitor, and losartan, an angiotensin type 1 receptor antagonist, on the proliferation of peripheral blood mononuclear cells (PBMC) in patients with essential hypertension. Nine patients with a sitting diastolic blood pressure of > 95 mmHg and < 105 mmHg at the end of a 4-week placebo run-in period entered the double-blind phase of the study, which consisted of three 6-week periods during which patients were treated with placebo, enalapril (20 mg o.d.) or losartan (50 mg o.d.) The de novo synthesis of DNA, RNA and protein in PBMC was measured by [3H]-thymidine, [3H]-uridine or [3H]-leucine incorporation, respectively. Neither enalapril nor losartan affected the proliferation of PBMC measured as de novo synthesis of DNA, RNA and protein. Our data show that proliferation was not affected during angiotensin-converting enzyme inhibition with enalapril and angiotensin receptor type 1 antagonism with losartan.

Effect of telmisartan on angiotensin II-mediated collagen gel contraction by adult rat cardiac fibroblasts.

The possible contributions of the angiotensin receptor subtypes 1 and 2 on the angiotensin II-induced collagen gel contraction by adult rat cardiac fibroblasts were studied using the specific angiotensin receptor type 1 and 2 antagonists telmisartan and P-186, respectively. Cardiac fibroblasts (from normal male adult rats) from passage 2 were cultured to confluency and added to a hydrated collagen gel, with or without angiotensin II, angiotensin II plus telmisartan, or angiotensin II plus P-186 in Dulbecco's Modified Eagle's Medium containing 5% fetal bovine serum for 1, 2, or 3 days. Control gels containing adult rat cardiac fibroblasts showed a significant amount of contraction after 3 days of incubation, causing a contraction to 67.9 +/- 7.1% of the area after 1 day. Angiotensin II (10(-7) M) stimulated (p < or = 0.05) the contraction of collagen mediated by cardiac fibroblasts after 1, 2, or 3 days. Telmisartan (10(-7) M) completely blocked the angiotensin II-induced collagen contraction by cardiac fibroblasts. P-186 (10(-7) M) had no effect on the angiotensin II-induced collagen contraction by cardiac fibroblasts. Addition of telmisartan and P-186 alone did not affect the collagen gel contraction by cardiac fibroblasts. Our data demonstrate that the effects of angiotensin II on the collagen gel contraction by adult rat cardiac fibroblasts are angiotensin II type 1 receptor mediated because they were abolished by the specific angiotensin II type 1 receptor antagonist telmisartan but not by the specific angiotensin II type 2 receptor antagonist P-186.

Angiotensin II-induced stimulation of collagen secretion and production in cardiac fibroblasts is mediated via angiotensin II subtype 1 receptors.

The possible contributions of the angiotensin receptor subtypes 1 (AT1) and 2 (AT2) to angiotensin II (Ang II)-induced changes in collagen secretion and production were studied using the specific angiotensin AT1- and AT2-receptor antagonists telmisartan and P-186, respectively. Cardiac fibroblasts (from normal male adult rats) from passage 2 were cultured to confluency and incubated in the presence of 10(-10) to 10(-6) M Ang II in serum-free Dulbecco's MEM medium for 24 hours. Collagen production and secretion were assayed by'H-Proline incorporation; non-collagen production and secretion were also calculated. Ang II dose-dependently increased collagen secretion and production in rat adult cardiac fibroblasts in culture. Non-collagen secretion and production were also concentration-dependently increased by Ang II. Addition of 100 nmol/l Ang II increased (p<0.01) collagen secretion and production bv 75+/-6 (SEM)% and 113+/-23%, respectively, and non-collagen secretion and production by 65+/-6% and 57+/-16%, respectively. Pretreatment of cardiac fibroblasts with telmisartan completely blocked the Ang II-induced increase in collagen secretion (p<0.001) and production(p<0.05) and in non-collagen secretion (p<0.01) and production (p<0.01). P-186 had no effect on the Ang II-induced increase in collagen secretion and production. Addition of telmisartan and P-186 did not affect collagen secretion and production in basal cardiac fibroblasts. Our data demonstrate that the effects of Ang II on collagen secretion and production in adult rat cardiac fibroblasts in culture are AT1-receptor mediated, since they were abolished by the specific AT1-receptor antagonist, telmisartan, but not by the specific AT2-receptor antagonist, P-186.

Induction of cardiac fibrosis by transforming growth factor-beta(1).

The role of transforming growth factor-beta(1) (TGF-beta(1)) in the production and deposition of collagens and in the induction of gene expression in the myocardium in relation to the development of myocardial fibrosis will be discussed. Very low expression of TGF-beta(1) and collagen type I and III mRNA is seen in the normal rat heart. Both expressions are markedly increased in the infarcted heart and the levels of TGF-beta(1) mRNA precedes increases in mRNA levels for extracellular matrix (ECM) proteins, suggesting a possible role of TGF-beta(1) in remodeling processes in the myocardium. The TGF-beta(1) expression is normally only transient since continuous TGF-beta(1) overexpression seems to promote nonadaptive cardiac hypertrophy and myocardial fibrosis. In vitro, TGF-beta(1) induces an increase in collagen production and secretion and enhances the abundance of mRNA levels for collagen type I and III in rat cardiac fibroblasts in culture. TGF-beta(1) also stimulates in vivo the expression of ECM proteins and in vivo gene transfer of TGF-beta(1) can induce myocardial fibrosis. Increased myocardial TGF-beta(1) and ECM protein mRNA are found in myocardial fibrosis induced by angiotensin II infusion, by noradrenaline treatment, by isoprenaline infusion, and by long-term blockade of NO synthesis. In vivo antagonism of TGF-beta(1) by neutralizing anti-TGF-beta(1) antibodies or by proteoglycans prevents the increase in gene expression of ECM proteins and inhibits myocardial fibrosis, suggesting that the increases in matrix protein production and fibrosis are mediated by TGF-beta(1).

Induction of cardiac fibrosis by angiotensin II.

The possible contributions of the angiotensin receptor subtypes 1 (AT1) and 2 (AT2) to angiotensin II-induced changes in collagen secretion and production were studied using the specific angiotensin receptor AT1 and AT2 antagonists telmisartan and P-186. The role of the renin-angiotensin system and its interaction with transforming growth factor-beta 1 (TGF-beta 1) in collagen deposition in cardiac fibroblasts in relation to the development of myocardial fibrosis is also discussed. Cardiac fibroblasts (from normal male adult rats) from passage 2 were cultured to confluency and incubated in the presence of angiotensin II (ANG II) in a concentration range of 10(-10)-10(-6) M in serum-free Dulbecco's MEM medium for 24 h. Collagen production and secretion were assayed by [3H]-proline incorporation and noncollagen production and secretion were also analyzed. ANG II dose-dependently increased collagen secretion and production in rat adult cardiac fibroblasts in culture. Noncollagen secretion and production were also concentration-dependently increased by ANG II. Addition of 100 nmol/l ANG II increased (p < 0.01) collagen secretion and production by 75 +/- 6 (SEM) and 113 +/- 23%, respectively, and noncollagen secretion and production by 65 +/- 6 and 57 +/- 16%, respectively. Pretreatment of cardiac fibroblasts with telmisartan completely blocked the ANG II-induced increase in collagen secretion (p < 0.001) and production (p < 0.05) and in noncollagen secretion (p < 0.01) and production (p < 0.01). P-186 had no effect on the ANG II-induced increase in collagen secretion and production. Addition of telmisartan and P-186 did not affect collagen secretion and production in basal cardiac fibroblasts. TGF-beta 1 also concentration- and time-dependently increased the secretion and production of collagen in cardiac fibroblasts. Our data demonstrate that the effects of ANG II on collagen secretion and production in adult rat cardiac fibroblasts in culture are AT1-receptor mediated since they were abolished by the specific AT1-receptor antagonist telmisartan but not by the specific AT2-receptor antagonist P-186. The ability of ANG II to induce collagen synthesis in cardiac fibroblasts may be mediated by increased TGF-beta 1 production.

Transforming growth factor-beta(1) induces angiotensin-converting enzyme synthesis in rat cardiac fibroblasts during their differentiation to myofibroblasts.

OBJECTIVES: Appearance of angiotensin-converting enzyme (ACE) in fibrotic tissue can be the result of the action either of one particular growth factor or of cross-talk between multiple factors. Transforming growth factor-beta1 (TGF-beta(1)) is an effective inducor of the differentiation of cultured fibroblasts to myofibroblasts, which are heterogeneous cells with different phenotypes. The present study investigated whether TGF-beta(1) is able to induce, in vitro, the differentiation of cultured fibroblasts to myofibroblasts with a phenotype containing ACE. DESIGN: Adult rat cardiac ventricular fibroblasts were obtained from hearts perfused with collagenase. Cells from second passage were always used. Rat cardiac ventricular fibroblasts were incubated with TGF-beta(1) (10 ng/ml) for seven days. Cell characterisation was performed using light microscopy and indirect immunostaining. Presence of vimentin, desmin, factor VIII, alpha-smooth muscle actin, and ACE was checked with both immunostaining and Western blotting. ACE activity was measured fluorometrically with hippuryl-histidyl-leucine as substrate. Synthesis of DNA was measured as (3)H-thymidine incorporation. RESULTS: Fibroblasts contained two types of activity of hip-his-leu degradation, namely a lisinopril-dependent activity (ACE activity) and a lisinopril-independent activity ('ACE-like' activity) which is performed by peptidase(s) other than ACE. The ACE activity constituted approximately 30% of the total activity. TGF-beta(1) induced an increase in both ACE activity and ACE protein (detected by immunoblotting) by 4.5 +/- 0.9- and 6.9 +/- 2.0-fold, respectively (p<0.05). This induction of ACE was accompanied by a profound modification of the fibroblasts phenotype, which consisted of a change in cell morphology, an enlargement of cell volume and an increase in cell protein content. TGF-beta(1) profoundly inhibited (3)H-thymidine incorporation and the number of cells in growing cultures. The induction of alpha-smooth muscle actin by TGF-beta(1) (6.8 +/- 2.8-fold increase, p<0.05) simultaneously with these modifications in cell morphology and proliferation indicates the appearance of myofibroblasts. These myofibroblasts did not contain desmin. CONCLUSION: TGF-beta(1) is able to induce the appearance of ACE in cultures of adult rat cardiac ventricular fibroblasts. The appearance of the enzyme is accompanied by the differentiation of fibroblasts to myofibroblasts.

Opposite associations of circulating aldosterone and atrial natriuretic peptide with left ventricular diastolic function in essential hypertension.

It has been shown in animal experiments that angiotensin II and aldosterone have mitogenic effects on the cardiovascular system, whereas atrial natriuretic peptide has antimitogenic properties. The aim of the present study was to relate plasma renin activity, angiotensin II, aldosterone and atrial natriuretic peptide to left ventricular structure and function, assessed by use of imaging echocardiography and transmitral Doppler velocimetry in 73 patients with essential hypertension, World Health Organization stages I-II, aged 43 +/- 10 (s.d.) years. Left ventricular mass, wall thickness and internal diameter were not independently related to the biochemical variables, except for a weak and positive association of wall thickness with plasma aldosterone (P = 0.06). However, left ventricular early inflow peak velocity and deceleration were independently and inversely related to age (P < 0.001) and to plasma aldosterone (P < 0.01), and positively to plasma atrial natriuretic peptide (P < 0.05). Peak flow velocity during atrial contraction was positively related to plasma atrial natriuretic peptide both before (P < 0.001) and after (P < 0.05) controlling for significant covariates (age, sex and blood pressure). We conclude that circulating renin, angiotensin II, aldosterone and atrial natriuretic peptide are not independently related to left ventricular mass in essential hypertension. The inverse association of plasma aldosterone with indices of diastolic function is compatible with a stimulating effect of aldosterone on myocardial fibrosis, which is opposed by atrial natriuretic peptide. The apparently conflicting positive association of this peptide with atrial peak velocity is most likely due to stimulation of its secretion by atrial involvement.

Reduction of left ventricular mass by antihypertensive treatment does not improve exercise performance in essential hypertension.

OBJECTIVE: To test the hypothesis that a reduction in left ventricular mass by long-term antihypertensive treatment, possibly associated with an improvement of diastolic function, would increase exercise performance in patients with essential hypertension. DESIGNS After a placebo run-in period, 27 patients with essential hypertension World Health Organization stages I and II were assigned randomly to 6-month double-blind treatment with either a diuretic (hydrochlorothiazide plus triamterene) or a converting enzyme inhibitor (trandolapril), to which the calcium antagonist amlodipine could be added after 3 months if required for better blood pressure control. METHOD: Investigations included clinic and ambulatory blood pressure measurements, left ventricular imaging and transmitral Doppler echocardiography and graded maximal exercise testing on the bicycle ergometer with respiratory gas analysis. RESULTS: Six-month antihypertensive therapy, which caused significant (P < 0.001) reductions in blood pressure (by 16% for clinic pressure) and in left ventricular mass (by 13%), but without convincing evidence of improved diastolic function, did not affect exercise performance or peak oxygen uptake. The influence on clinic, exercise and ambulatory blood pressures and on the peak oxygen uptake was similar in the two treatment arms but left ventricular wall thickness decreased to a greater extent in the trandolapril group (P< 0.05 at 3 months and P= 0.06 at 6 months). CONCLUSIONS: Regression of left ventricular mass caused by 6-month antihypertensive therapy does not improve exercise performance of patients with essential hypertension.

Nonlinear relationship between erythrocyte sodium-lithium countertransport and blood pressure in man.

A relationship between erythrocyte Na+/Li(+)-countertransport activity and blood pressure was studied in a randomly selected sample (95 subjects) with full range of blood pressure, from a representative group of inhabitants of one of Moscow's districts. The mean rate of erythrocyte Na+/Li(+)- countertransport activity was higher (p < 0.01 or less) in the groups of subjects with both borderline (BH) and moderate essential hypertension (EH) as compared with the group of normotensives (NT). A positive correlation was found between the erythrocyte Na+/Li(+)- countertransport rate and age and body weight in the entire selected group. The total contribution of these confounding parameters is responsible for 20.4% of the interindividual variability of the Na+/Li(+)- countertransport activity. The individual Na+/Li(+)- countertransport values remained unchanged during at least 2 years of follow-up. A nonlinear relationship between erythrocyte Na+/Li(+)- countertransport activity and blood pressure was established in the entire group. No significant association between blood pressure and Na+/Li(+)- countertransport was seen at high and low values of these two parameters. A pronounced change in the erythrocyte Na+/Li(+)- countertransport values occurred within a narrow borderline blood pressure range.

Red blood cell sodium-lithium countertransport in patients with essential and renal hypertension.

The erythrocyte Na+/Li(+)-countertransport activity was studied in patients with essential hypertension (n = 59), chronic glomerulonephritis (n = 30), chronic pyelonephritis (n = 26), renovascular hypertension (n = 35) and pheochromocytoma (n = 3). The erythrocyte Na+/Li(+)-countertransport (SLC) activity was on average higher (p < 0.02) in the patients with essential hypertension as compared to those with secondary hypertension, although a clear distinction between both groups was not possible. After surgical treatment of the patients with atherosclerotic renal artery stenosis, fibromuscular dysplasia or pheochromocytoma, no change in erythrocyte SLC activity was observed. However, blood pressure was significantly reduced.

Transfer of cadmium from a sandy acidic soil to man: a population study.

This population study included 230 subjects (age range 20-83 years) who consumed vegetables grown in kitchen gardens on a sandy acidic soil (mean pH approximately 6.3). The study investigated the association between the Cd (cadmium) levels in blood and urine and the Cd concentration in the soil (range 0.2-44 ppm). Seventy-six subjects were current smokers and 122 participants lived in a district with known Cd pollution. Urinary Cd in the 230 subjects averaged 8.7 nmole/24 hr, (range 1.3 to 47 nmole/24 hr) after age adjustment positively correlated with the Cd level in the soil; a twofold increase of the Cd concentration in the soil was accompanied by a 7% rise in urinary Cd in men (R2 = 0.05; P = 0.04) and by a 4% rise in women (R2 = 0.02; P = 0.05). Blood Cd averaged 11.5 nmole/liter (range 1.8-41 nmole/liter) and was negatively associated with the Cd level in the soil. After adjustment for significant covariates (smoking and serum gamma-glutamyl transpeptidase in both sexes, and age and serum ferritin in women), a twofold increase in the Cd concentration in the soil was accompanied by a 6% decrease in blood Cd in men (R2 = 0.03; P = 0.09) and by a 10% decrease in women (R2 = 0.06; P less than 0.01). In conclusion, in a rural population, consuming vegetables grown on a sandy acidic soil, 2 to 4% of the variance of urinary Cd was directly related to the Cd level in the soil. The negative correlation with blood Cd, a measure of more recent exposure, was biased by the implementation of preventive measures in the polluted district.

Comparison of the effects of isradipine and lisinopril on left ventricular structure and function in essential hypertension.

The effects on cardiac structure and function of antihypertensive regimens with different effects on the renin-angiotensin system were compared. In a 1-year study, 32 patients with essential hypertension were randomized to treatment with either the converting enzyme inhibitor lisinopril or the calcium antagonist isradipine; hydrochlorothiazide could be added. Blood pressure (BP) decreased significantly (p less than 0.001) and similarly in the 2 treatment groups. Left ventricular (LV) mass was already significantly reduced after 16 weeks of treatment (p less than 0.001) and remained decreased thereafter, with no difference in the response to the 2 treatment regimens. The change in LV mass was related to the decrease in systolic BP for the total study group (p less than 0.001) and for each treatment group separately. During the 3-week run-out period on placebo, BP and LV mass increased again (p less than 0.01). Afterload decreased during active treatment (p less than 0.001), and fractional shortening of the LV internal diameter was significantly increased (p less than 0.01) to a similar extent in both groups. The ratio of peak mitral flow velocities during atrial contraction and early filling was reduced after 1 year of active treatment in the total study group (p less than 0.01); this change was similar in both groups. The data suggest that the regression of LV mass during antihypertensive therapy is mainly related to the decrease in systolic BP.

Mean and range of the ambulatory pressure in normotensive subjects from a meta-analysis of 23 studies.

To perform a meta-analysis of published reports in an attempt to determine the mean and range of normal ambulatory blood pressure (BP), 23 studies including a total of 3,476 normal subjects were reviewed. Most studies were compatible with a mean 24-hour BP in the range of 115 to 120/70 to 75 mm Hg, a mean daytime BP of 120 to 125/75 to 80 mm Hg, and a mean nighttime BP of 105 to 110/60 to 65 mm Hg. With weighting for the number of subjects included in the individual studies, the 24-hour BP averaged 118/72 mm Hg, the daytime BP 123/76 mm Hg, and the nighttime BP 106/64 mm Hg. The night/day pressure ratio averaged 0.87 for systolic and 0.83 for diastolic BP, with ranges across the individual studies from 0.79 to 0.92 and from 0.75 to 0.90, respectively. If the mean +/- 2 standard deviation interval in the various studies was considered normal, the range of normality was on average 97 to 139/57 to 87 mm Hg for the 24-hour BP, 101 to 146/61 to 91 mm Hg for the daytime BP, and 86 to 127/48 to 79 mm Hg for the nighttime BP. Until the results of prospective studies on the relation between the ambulatory BP and the incidence of cardiovascular morbidity and mortality become available, the aforementioned intervals, which summarize the experience of 23 investigators, could serve as a temporary reference for clinical practice.

Measurement of individual angiotensin peptides by HPLC-RIA.

Immunoreactive measurements of Angiotensin II in plasma, relate to a variety of angiotensin peptides with different biological activities. A method is described to differentiate these individual angiotensin peptides. It involves extraction of the peptides from plasma by reversible adsorption to phenylsilyl silica cartridges, separation by an isocratic, ion pairing high-pressure liquid chromatography technique and measurement of the appropriate fractions by radioimmunoassay. In umbilical venous plasma molar concentrations of the smaller angiotensin fragments were found to range between 16 and 25% of the concentrations of the angiotensin II octapeptide. Because some angiotensin antisera show higher affinity for the smaller peptides than for the octapeptide, concentrations of angiotensin II, measured by radioimmunoassay, may be overestimated by up to 35% unless the various angiotensin peptides are adequately separated.