Nonhemodynamic Factors Research Articles

Influence of arterial blood pressure and aldosterone on left ventricular hypertrophy in moderate essential hypertension

In a group of 36 untreated patients with mild-to-moderate essential hypertension (office systolic blood pressure [SBP] 160 ± 3.4 mm Hg, office diastolic blood pressure [DBP], 102 ± 1.5 mm Hg), 24-hour ambulatory blood pressure monitoring, and determination of left ventricular (LV) mass index according to the formula of Devereux were performed. After an overnight fast, blood samples were taken for the determination of serum aldosterone levels and plasma renin activity. Urinary catecholamine concentrations were assayed from 24-hour urine collections. Left ventricular mass index (143.7 ± 8 g/m 2) did not correlate significantly with either office SBP or office DBP. The correlation of LV mass index with mean 24-hour SBP (145 ± 3 mm Hg) was statistically significant: r = 0.395, p = 0.026. However, the best correlation was obtained with mean 24-hour DBP (90 ± 3 mm Hg) with r = 0.499 (p = 0.004). Urinary catecholamine levels did not correlate with LV mass index. In addition, LV mass index correlated significantly with plasma renin activity (r = 0.346, p = 0.050) and serum aldosterone levels (r = 0.559, p = 0.0009). There was a strongly significant correlation between LV mass index and serum aldosterone levels even after adjustment for mean 24-hour SBP (r = 0.496, p = 0.005) and DBP (r = 0.514, p = 0.004). These results demonstrate that ambulatory blood pressure determinations but not office blood pressure parameters correlate well with left ventricular hypertrophy in essential hypertension. Nonhemodynamic factors are important determinants of left ventricular mass as well. Moreover, aldosterone seems to play an important rote in cardiac hypertrophy independent of its relation with arterial blood pressure.

Glomerular abnormalities in long-term experimental diabetes. Role of hemodynamic and nonhemodynamic factors and effects of antihypertensive therapy.

To evaluate the role of glomerular hypertension, glomerular hypertrophy, glomerular lipid deposition, and plasma cholesterol levels in diabetic glomerulopathy, Munich-Wistar rats received streptozocin and daily insulin injections and were assigned to one of three groups: untreated diabetic (DMC), hydralazine-treated diabetic (DMH), and enalapril-treated diabetic (DME). Age-matched control rats were also studied. At 6-10 wk of diabetes, DMC rats showed marked elevations of glomerular pressure and glomerular filtration rate as well as slight glomerular enlargement and cholesterol elevation. DMH and DME rats exhibited arterial hypotension but no change in cholesterol or glomerular volume. Glomerular pressure was normalized by enalapril but not by hydralazine treatment. Additional rats were followed up to 12 mo of diabetes. Slight hypertension was seen in DMC rats, whereas sustained hypotension occurred in DMH and DME rats. Progressive albuminuria occurred in DMC and DMH but not in DME rats. At 12 mo, glomerular hypertension persisted in DMC and DMH rats but was still absent in DME rats. Cholesterol was elevated in DMC and slightly lower in DMH and DME rats. Glomeruli were equally enlarged in the diabetic groups. Glomerular sclerotic lesions and lipid deposits appeared in DMC and DMH but not in DME rats. These findings are consistent with the notion that glomerular hypertension may promote glomerular injury in experimental diabetes. Glomerular lipid deposition may also participate in this process, although a causal relationship was not demonstrated. Glomerular hypertrophy and cholesterol were unrelated to glomerular injury, although they may have exacerbated hemodynamically mediated damage.

Glomerular abnormalities in long-term experimental diabetes. Role of hemodynamic and nonhemodynamic factors and effects of antihypertensive therapy

Glomerular abnormalities in long-term experimental diabetes. Role of hemodynamic and nonhemodynamic factors and effects of antihypertensive therapy

Influence of Nonhemodynamic Factors on the Microcirculation in Moderate Arterial Essential Hypertension

This study is aimed at examining the role of non-hemodynamic factors on the impaired microcirculation in patients with moderate essential hypertension. In a series of 31 patients (mean age, 47.8 +/- 1.1 years) with newly diagnosed untreated moderate essential hypertension (mean systolic blood pressure 161.7 +/- 2.0 mm Hg, mean diastolic blood pressure 102.4 +/- 1.5 mm Hg), parameters of the capillaroscopic examination of the finger microcirculation (mean number of capillaries, NRCAP), length of the capillaries (LECAP, microns), diameter micron) of the efferent (EFDI) and afferent (AFDI) apillaries, and mean red blood cell velocity (RBCV, microns/sec), which was measured by the flying spot technique, were correlated with a number of hormones (sampled after an overnight fast) including: plasma renin activity, aldosterone, and parathyroid hormone (PTH). A significant correlation (P less than .05) could be obtained between several parameters of the microcirculation and PTH:PTH (23.8 +/- 1.4 pg/mL)-NRCAP (14.9 +/- 0.5): r = -0.440, P = .013; PTH-AFDI (4.0 +/- 0.5 microns): r = 0.442, P = .012; PTH-EFDI (2.8 +/- 0.5 microns): r = 0.416, P = .019; PTH-RBCV (711 +/- 69 microns/sec): r = -0.351, P = .05. Furthermore, 24-h urinary norepinephrine (U-NOR) and afferent and efferent diameter of the capillaries intercorrelated significantly: U-NOR (46.0 +/- 6.2 micrograms/24 h)-AFDI: r = 0.439, P = .034; U-NOR-EFDI; r = 0.462, P = .025. This study shows that in patients with moderate essential arterial hypertension nonhemodynamic factors have an influence at the level of the microcirculation.

Influence of the arterial blood pressure and nonhemodynamic factors on left ventricular hypertrophy in moderate essential hypertension

In a group of 36 untreated patients with mild to moderate essential hypertension (office systolic and diastolic blood pressures (BPs) 160 ± 3.4 and 102 ± 1.5 mm Hg, respectively), a 24-hour ambulatory BP monitoring and determination of left ventricular (LV) mass index according to the formula of Devereux were performed. After an overnight fast, blood samples were taken for the determination of serum aldosterone, plasma renin activity and serum parathyroid hormone. Urinary catecholamines were sampled for 24 hours. LV mass index (143.7 ± 8 g/m 2) did not correlate significantly either with office systolic or diastolic BP. The correlation of LV mass index with mean 24-hour systolic BP (145 ± 3 mm Hg) was statistically significant: r = 0.395, p = 0.026. However, the best correlation was obtained with mean 24-hour diastolic BP (90 ± 3 mm Hg) with r = 0.500 (p = 0.004). Urinary catecholamines were not correlated with LV mass index. LV mass index correlated significantly with plasma renin activity (r = 0.346, p = 0.050), and aldosterone (r = 0.559, p = 0.001). There was a very significant correlation between LV mass index and parathyroid hormone (r = 0.719, p = 0.00001) even after adjustment for mean 24-hour systolic and diastolic BPs. These results clearly demonstrate that ambulatory BP determinants but not office BP parameters are well correlated with LV hypertrophy in essential hypertension. Nonhemodynamic factors are important determinants of LV mass as well. Besides the renin-angiotensin-aldosterone system, parathyroid hormone appears to play an important role in cardiac hypertrophy.

Antihypertensive therapy and the progression of chronic renal disease. Are there renoprotective drugs?

The pathogenesis of hypertensive glomerular injury is complex, involving both hemodynamic and nonhemodynamic factors. One can therefore confidently predict that a wide variety of disparate therapeutic interventions, pharmacologic and nonpharmacologic, may be effective in arresting or slowing progressive glomerular injury. Based on the experimental and clinical literature available to date, it is clear that glomerular capillary hypertension is an important pathogenetic factor in this disease and that lowering of Pgc with antihypertensive drugs is associated with prevention of glomerular injury. Furthermore, the CEI may have a special renoprotective effect compared to other antihypertensive agents, most likely due to their unique renal hemodynamic actions. Pending the results of well-designed clinical trials, converting enzyme inhibitors represent the antihypertensive agents most likely to arrest the progressive decline in renal function observed in patients with hypertension and chronic renal failure. The calcium channel blockers are effective antihypertensive agents in patients with chronic renal failure, but whether they confer specific renoprotective effects remains uncertain. Since a large number of patients with chronic renal failure require more than one antihypertensive drug for adequate blood pressure control it may be of interest to evaluate the benefits of drug combinations. In this regard, it is possible that a combination of a CEI and a CCB may have complimentary effects in protecting the kidney. The development of these new classes of antihypertensive agents has had a major impact on the treatment of patients with chronic progressive renal failure. Future studies will hopefully clarify the optimal antihypertensive therapeutic regimen and allow us to move closer to the goal of eliminating end-stage renal failure.

Is reversal of left ventricular hypertrophy in hypertension beneficial?

The left ventricle increases its mass and wall thickness in hypertension as a result of the progressive increase in hemodynamic overload offered by increasing arterial blood pressure and total peripheral resistance. However, evidence is increasing that nonhemodynamic factors may also be important in the development of left ventricular hypertrophy (LVH). This LVH resulting from hypertensive disease conveys an independent risk of premature cardiovascular morbidity and mortality. The specific mechanisms accounting for this increased risk are not known with assurance, although several mechanisms are under active study; they include more prominently ventricular dysrhythmias and myocardial ischemia. It is possible to diminish the increased left ventricular mass with pharmacological agents, although currently it is not known whether this reversal also diminishes the risk associated with LVH. Therefore, at the present time the best means for preventing the risk of LVH is to prevent its development in the first place, and this seems to be preventable through control of arterial blood pressure at the earliest stages of hypertension. Risk may also be diminished in patients with existing LVH who are receiving digitalis or diuretics or who have chronic fluid- and electrolyte-disturbing diseases. Under these circumstances, the careful use and selection of antihypertensive therapy and control of electrolyte balance no doubt will prevent unnecessary morbidity and mortality.

Renal protective effects of angiotensin converting enzyme inhibition

Nephron loss is a common progression of a diverse range of kidney diseases. Recent experimental models of chronic renal disease have suggested that hemodynamic and nonhemodynamic mechanisms play key roles in progressive renal injury. Extensive renal ablation in the rat was followed by development of altered glomerular hemodynamics. Albuminuria and histologic damage leading to focal glomerulosclerosis were preceded by the development of increased glomerular pressures and were prevented by interventions such as severe dietary protein restriction and angiotensin-converting enzyme (ACE) inhibitor therapy. Both experimental interventions ameliorated glomerular hypertension. It was therefore concluded that these interventions ameliorated injury by glomerular hemodynamic effect. Similar findings were obtained in a rat model of type I diabetes mellitus induced by streptozotocin in which glomerular hemodynamic factors appeared important to the development of progressive renal disease. Recent studies have suggested that nonhemodynamic factors have important roles in the progression of glomerular injury. For example, although the predominant effects of ACE inhibitor therapy appear to be hemodynamically mediated, data are emerging which suggest that these agents may also influence growth/proliferation of glomerular cells. Because hyperplasia/hypertrophy may influence glomerular susceptibility to injury, this may also be a potential mechanism whereby ACE inhibitor therapy influences glomerular damage. In addition, a variety of studies have suggested that hyperlipidemia, which is a frequent accompaniment of glomerular disease, is an important modulator of glomerular injury independent of glomerular hemodynamic effects. Coagulation factors, calcium phosphorus balance, as well as the genetic susceptibility of the glomerulus to injury, all appear to contribute to progressive nephron destruction.

High protein intake accelerates glomerulosclerosis independent of effects on glomerular hemodynamics

It is unclear whether glomerular hemodynamic changes always accompany alterations in dietary protein, and whether nonhemodynamic factors associated with a high protein intake can influence glomerular injury. In the present study, uninephrectomized (UNx) male rats were fed either standard (20%) or high (40%) protein diets. Body growth was comparable in the two diet groups. At 30 weeks of age, UNx rats fed high protein had increased albuminuria (36.7 +/- 12.6 mg/24 hr), compared to UNx rats fed standard protein (10.2 +/- 6.2 mg/24 hr; P less than 0.05). The incidence of focal glomerulosclerosis (FGS) at 36 weeks was markedly increased in the high protein rats (19.0 +/- 7.7%), compared to the standard protein rats (3.2 +/- 2.0%; P less than 0.05). Moreover, FGS in the high protein rats correlated with the serum cholesterol level measured at 18, 24, and 30 weeks of age. Glomerular hemodynamics were assessed before glomerular injury developed in separate groups of UNx rats fed either standard or high protein. Single nephron GFR (SNGFR) and single nephron plasma flow (SNPF) were increased in UNx rats, compared to two-kidney rats fed standard protein. SNGFR and SNPF, however, were not different between UNx rats fed standard or high protein. Glomerular capillary pressure (PGC) was not different between UNx rats fed standard protein (51.7 +/- 1.3 mm Hg) and two-kidney controls (53.1 +/- 1.5 mm Hg). Moreover, PGC was not altered in UNx rats fed high protein (51.8 +/- 1.6 mm Hg). We conclude that high dietary protein can accelerate the development of glomerular injury independent of effects on glomerular hemodynamics.

Overview of hemodynamic and non-hemodynamic factors associated with left ventricular hypertrophy

The role of the heart in hypertension has finally emerged as a major issue of cardiovascular concern by the clinician, physiologist, pharmacologist, biochemist, and molecular biologist. This discussion provides an overview of the present state of knowledge and current areas of investigation in this active area of broad interest. Generally, these relate to: the active participation of the heart (e.g. hemodynamic, humoral, autocrine/paracrine); the adaptive response of the heart (i.e. hemodynamic); non-hemodynamic relationships (vis-a-vis, age, race, gender, humoral, coexistent disease); and current thoughts on mechanisms of so-called regression of left ventricular hypertrophy. Several antihypertensive classes of compounds are characterized by decreasing cardiac mass and left ventricular wall thicknesses. The angiotensin converting enzyme inhibitors are included among these agents; their physiological effects in producing "regression" are under active study as are the mechanisms responsible for these changes. These concerns are no longer of incidental or theoretical interest but have major impact on selection of antihypertensive therapy and the management of the patient with hypertension. Thus, the heart may participate actively in the pathogenesis and maintenance of the disease; it adapts to the vascular disease hemodynamically; but in this regard the response has both positive beneficial concerns as well as negative implications as an independent risk factor. These latter concerns should be explored in great depth before conclusions are made with respect to the long-term implications of antihypertensive therapy on the heart.

Liver Function Abnormalities in Chronic Heart Failure

To characterize the incidence and severity of liver function abnormalities in patients with congestive heart failure, we analyzed systemic hemodynamics and biochemical profiles in 133 patients with stable chronic congestive heart failure, secondary to a dilated cardiomyopathy. The patients were divided into three groups, based on the severity of the reduction in cardiac index (CI). The mean values of all liver function tests in groups 1 (n = 43; CI greater than or equal to 2.0 L/min/m2) and 2 (n = 48; CI greater than 1.5 and less than 2.0 L/min/m2) were essentially normal, except for minimally elevated alkaline phosphatase levels and slightly decreased albumin levels in both groups, and slight increases in levels of gamma-glutamyl transpeptidase and total bilirubin in group 2. In contrast, group 3 patients (n = 42; CI less than or equal to 1.5 L/min/m2) had the most severe heart failure, as assessed by the lowest CI and highest cardiac filling pressures, and significantly higher levels of aspartate aminotransferase (65 +/- 82 U/L), alanine aminotransferase (77 +/- 102 U/L), lactate dehydrogenase (282 +/- 91 U/L), and total bilirubin (29 +/- 14 mumol/L [1.7 +/- 0.8 mg/dL]). The percentage of patients in group 3 with these abnormalities ranged between 27% and 80%. Although linear regression analysis showed that the elevations in right atrial and pulmonary wedge pressures, and the decreases in CI, were significantly correlated with liver function abnormalities, the correlation coefficients were small. Thus, liver function abnormalities remain common in patients with congestive heart failure but are generally small in magnitude and not associated with clinically apparent hepatic disease. It is likely that reduced forward flow and passive backward congestion are both contributing factors in the pathogenesis of these biochemical abnormalities, although nonhemodynamic factors may also be important.

Adrenergic receptor characteristics of cardiac myocytes cultured in serum-free medium: Comparison with serum-supplemented medium

Neonatal rat ventricular myocytes cultured in serum-free medium coexpress both α 1 and β 1 receptors as determined by radioligand binding studies. In cells exposed to serum for 48 hr surface area increased 3.69 fold, but the maximum number of binding sites ([ 125I]-iodocynanopindolol) only increased 1.5 fold from 12956 ± 7579 to 19676 ± 5181 sites/cell (n=5, p<.05) yielding a value of 2.48 sites/um 2 for cells grown in serum-supplemented medium compared with 6.96 sites/um 2 for cells grown in serum-free medium. Thus serum-induced hypertrophy is associated with a decrease in β 1 receptor density relative to cell size; however, adenylate cyclase response is unaffected. This cell culture system constitutes an excellent model for studying interventions that may influence the regulation of cardiac myocyte hypertrophy by nonhemodynamic factors, particularly through the adrenergic receptor system.

Myocyte hypertrophy in neonatal rat heart cultures and its regulation by serum and by catecholamines.

The role of hormones and other humoral factors in the regulation of myocardial hypertrophy has been difficult to evaluate. We asked whether myocardial cell hypertrophy could be demonstrated in cultures from the day-old rat ventricle and evaluated the effect of serum concentration and catecholamines on the growth process. Two single-cell preparations were used: serum-supplemented, bromodeoxyuridine-treated cultures and serum-free cultures with transferrin and insulin. Both preparations were characterized by myocardial cell predominance (about 75--80% of total cells) and constant cell numbers. Myocardial cell size was documented by photomicroscopy and quantified by volume (microscopic diameter of suspended cells), surface area (planimetry of attached cells), and total cell protein concentration (Lowry method and cell counts). Growth was also evaluated in pure nonmyocardial cell cultures. In cultures with 5% (vol/vol) serum, myocardial cell size increased 2- to 3-fold over 11 days in culture. Final volume, surface area, and protein concentration were about 3000 micrometer3/cell, 5000 micrometer2/cell, and 1500 pg/cell, respectively. Serum had a dose-related effect on myocardial cell hypertrophy; myocardial cell size increased about 4-fold when serum concentration was increased from 0% to 5% or 10%. Cells maintained in serum-free medium with transferrin and insulin (each 10 microgram/ml) did not hypertrophy, but did remain responsive to the growth-promoting activity of serum. Chronic exposure to isoproterenol or norepinephrine (1 microM) significantly stimulated myocardial cell hypertrophy. This stimulation was dose-related, was not blocked by equimolar propranolol, was not associated with a sustained chronotropic effect, and was more pronounced in the serum-free preparation. In pure cultures of nonproliferating (bromodeoxyuridine-treated) nonmyocardial cells, cell size also increased with time in culture, but variation in serum concentration and addition of norepinephrine had no significant effect on cell size. Myocardial cell hypertrophy occurs in culture and is regulated by variations in the culture medium, including serum, with its contained hormones and growth factors, and catecholamines. The culture preparation can be used to explore the regulation of myocardial cell hypertrophy by nonhemodynamic factors.