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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the first part of the text the main elements of renal physiology are mentioned as well as the role played by sodium-modulating hormones in the preservation of sodium and water homeostasis. A personal contribution concerns the release as well as the circadian rhythm of atrial natriuretic peptide (ANP) and of the digitalis-like substance (DLS). In the second part, the problem is dealt with from a pathophysiologic point of view, with reference made to the literature, and to our own data. In particular, the problem of essential hypertension with reduced levels of plasma renin activity (PRA) is thoroughly analyzed. As is well known, this kind of hypertension is characterized by normal plasma aldosterone levels associated with reduced kallikrein urinary excretion. The data we gathered not only confirmed these findings but also enabled us to point out other typical features of this particular kind of hypertension: normal values of vasopressin, elevation of ANP and DLS, hyperactivity of Na+/K+ cotransport. The introduction of a single variant in the sodium-modulating systems confirmed that the low PRA patient also behaves distinctively from a dynamic point of view. In fact, prostaglandin inhibition determines hypertension only in these patients, while both oral kallikrein administration and intravenous ANP administration were particularly effective because of a primitive deficit of the natriuretic paracrine systems paralleled by a compensatory increase of ANP. After identifying this group of hypertensive patients we intended to ascertain whether, even in the normal or high PRA patients, it was possible to identify a sub-group of subjects with altered sodium-modulation. The patients we examined were subdivided according to their hormonal and renal response to a saline load, and to angiotensin II, into "modulators" (with normal) and "nonmodulators" (with reduced sodium excretion capacity). An analysis of the hormonal characteristics of non-modulators identified an increased responsiveness of all sodium-modulation systems and not only of the renin-angiotensin-aldosterone system as pointed out by some other authors. The last part of the text is devoted to clinical and therapeutic problems. The behaviour of the daily blood pressure profile in patients with essential hypertension, and then the influence that sodium-modulating systems may have on pressure are discussed. The consequences of a progressive reduction in renal function on the circadian rhythm of arterial pressure are then assessed, and, at the same time, how renal impairment parallels the flattening of the daily pressure rate is observed.
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PMID:The kidney and essential hypertension. 183 73

The relationships between atrial natriuretic peptide (ANP) and the renal sodium-modulating systems have not yet been completely examined. In particular, the relationships between ANP and the kinins system are almost unknown. We thus examined an extremely selected cohort of normotensive (n = 29, mean age 21 +/- 2 years) and hypertensive subjects (n = 51m mean age 21 +/- 2.9 years), both without hypertensive heredity. After 7 days under normal sodium intake (120 mEq of Na+/day), blood samples were taken in the morning on awaking, for radioimmunoassay of plasma levels of aldosterone, ANP and renin activity. Blood was again drawn after one active hour in orthostatism. We also evaluated urinary kallikrein excretion from urine collected over the previous 24 hours. Our results showed higher plasma levels of ANP in young hypertensives than in normotensives (statistical significance p less than 0.0025). Urinary excretion of kallikrein was markedly reduced (p less than 0.001) in the hypertensive group (0.46 +/- 0.3 U/24 h) compared to youths with normal blood pressure (0.79 +/- 0.24 U/24 h), in which a relationship between plasma ANP and urinary kallikrein was not evident; young hypertensives, on the other hand, showed an inverse correlation (r = -0.72; p less than 0.001). Finally, our investigation, aside from establishing the presence of high circulating ANP levels even at the initial phases of hypertension, points out a new possible means of feedback among sodium-modulating systems. The opposite relationship between ANP and urinary kallikrein excretion in young hypertensives could be attributed to reduced activity of the renal kinins system and a compensatory attempt on the part of ANP.
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PMID:[Correlations between circulation levels of natriuretic atrial peptide and urinary excretion of kallikrein in young normotensive and hypertensive subjects]. 183 37

The effects of cyclosporine A treatment on arterial pressure and renal function were assessed in 11 young patients with type I diabetes of short duration. Cyclosporine was started at 7.5 mg/kg/day, progressively decreased to 6.3 mg/kg/day at 6 months, and then continued at a lower dose (4.1 mg/kg/day) for an additional 3 months in patients in whom remission of insulin dependency was obtained (n = 6). After 3 months of cyclosporine, a slight but significant increase in arterial pressure (+5.2 +/- 1.5 mm Hg), a rise in renal vascular resistance (approximately 20%), a decrease in glomerular filtration rate (approximately 25%), and a fall in filtration fraction were observed. Such changes were sustained after 6 and eventually 9 months of therapy. The decrease in glomerular filtration rate observed during cyclosporine treatment contrasted with the lack of change in simultaneously estimated creatinine clearance; in fact, the creatinine clearance/glomerular filtration ratio increased from 1.07 +/- 0.05% to 1.33 +/- 0.09% within 3 months of cyclosporine therapy, thus suggesting an enhanced tubular secretion of creatinine. Plasma renin activity and urinary excretion of kallikrein decreased significantly (approximately 50%), whereas plasma aldosterone concentration remained unaltered and plasma concentration of potassium increased during cyclosporine therapy. These changes were observed in the presence of a constant urinary excretion of sodium and potassium and a constant body weight. All parameters returned to pretreatment values within 3 months after cessation of cyclosporine. These results indicate that cyclosporine given for 6-9 months at a moderate dose causes a deleterious but reversible effect on arterial pressure and renal function in young diabetic patients.
Hypertension 1991 Sep
PMID:Renal changes associated with cyclosporine in recent type I diabetes mellitus. 188 46

Vasoactive hormones acting as endocrine, neuroendocrine, or local hormonal systems (intracrine, autocrine, and paracrine) are an important component of the many factors that regulate blood pressure. Hypertension may be the result of an alteration in the balance between vasodepressor and vasopressor hormonal systems. Changes in this balance could be due to genetic factors such as mutations in one of the genes of the vasoactive system or environmental factors that alter the synthesis and release of one or more vasoactive hormones. Endocrine and neuroendocrine vasopressor hormonal systems, such as the renin-angiotensin system and catecholamines, play a well-established and important role in the regulation of blood pressure and the pathogenesis of some secondary forms of hypertension. The blockade of such systems has already resulted in effective antihypertensive treatment. The role of local hormonal systems is less well established; however, recent evidence suggests they also play an important role in the regulation of blood pressure and the pathogenesis of hypertension. Some vasopressor hormonal systems, such as the renin-angiotensin system, can act as both endocrine or local hormonal systems. Work using transgenic rats harboring the mouse Ren-2 gene has conclusively demonstrated that the renin-angiotensin system, acting as a local hormonal system, has the capability to cause severe hypertension. Whether this model of experimental hypertension mimics any type of human hypertension is not known. Vasodepressor hormones such as kinins, prostaglandins, and endothelium-derived relaxing factor (EDRF) act mainly as local hormonal systems, with the notable exception of atrial natriuretic factor, which may act as both an endocrine and a local hormone. The tissue kallikrein-kinin system, acting either directly or via paracrine eicosanoids or EDRF, participates in local regulation of the circulation, renal function, and the acute antihypertensive effect of angiotensin converting enzyme inhibitors. A restriction fragment length polymorphism (RFLP) that distinguishes the kallikrein gene family of a strain of spontaneously hypertensive rats (SHR) from normotensive Brown Norway rats has been identified. In a set of 32 recombinant inbred strains derived from these SHR and Brown Norway strains, the RFLP marking the kallikrein gene family of SHR cosegregated with an increase in blood pressure. Also, in a study of Utah families it was found that a dominant-allele kallikrein gene expressed as high urinary kallikrein excretion was associated with a decreased risk of essential hypertension. In conclusion, vasopressor and vasodepressor hormones, acting not only as endocrine but also as local hormones, play an important role in the regulation of blood pressure and the pathogenesis of hypertension.(ABSTRACT TRUNCATED AT 400 WORDS)
Hypertension 1991 Sep
PMID:Local hormonal factors (intracrine, autocrine, and paracrine) in hypertension. 188 59

Arachidonic acid (AA) can be metabolized to an array of products affecting biological mechanisms such as those governing vascular reactivity and transport function. Metabolism of AA by cyclooxygenase in the nephron is discretely localized and is overshadowed in some nephron segments by a considerable capacity to generate P-450 AA metabolites. The synthesis of renal P-450 AA products is increased in hypertension. AA metabolites participate in fluid and electrolyte homeostasis and regulation of tissue blood flow and act as modulators of pressor systems. In addition, eicosanoids either augment or mediate the vasodilator-diuretic actions of the kallikrein-kinin system.
Hypertension 1991 Nov
PMID:Arachidonate metabolites and kinins in blood pressure regulation. 193 79

We detected a novel vasoconstrictor in an arginine esterase fraction separated from fractions containing tonin and other esterases that were obtained from a rat submandibular gland extract. When tested on isolated rabbit aorta rings, the substance caused dose-related contractions that were slow in onset, long-lasting, and difficult to reverse by rinsing. The substance acts directly on vascular smooth muscle, since preincubation with plasma or intact endothelium is not required. The fact that the constrictor was destroyed by heat and incubation with pronase suggests that it is a protein. Molecular sieving indicates an estimated molecular weight of 24,000 Da. It has a neutral isoelectric point that is higher than the pI of tonin, from which it can be separated by anion exchange chromatography. A small amount of the vasoconstrictor was obtained by gel filtration and eluted from isoelectric focusing polyacrylamide gels. The purified substance showed a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It was a potent vasoconstrictor; an estimated concentration of 2.5 nM induced contraction of isolated rabbit aorta rings ranging from 15% to 40% of the maximum contraction obtained by 60 mM KCl. Contraction was completely blocked by 1 mM (p-amidinophenyl)methanesulfonyl fluoride, a serine protease inhibitor. Contractile activity was not affected by hirudin, a thrombin inhibitor, but was completely inhibited by soybean trypsin inhibitor and blunted by aprotinin; thus it may be a trypsin-like serine protease. Purified vasoconstrictor preparation showed hydrolyzing activity on Pro-Phe-Arg-methyl-coumarin amide, a kallikrein substrate. We conclude that a novel vasoconstrictor serine protease is present in the rat submandibular gland.
Hypertension 1991 Jan
PMID:A potent vasoconstrictor in the rat submandibular gland. 198 78

Epidemiological evidence suggests that there is a close association between obesity, non-insulin-dependent diabetes (NIDDM) and hypertension. Obesity and NIDDM are the classical insulin-resistant states. Even in the absence of these conditions, essential hypertension is associated with insulin resistance. In view of the acute effects of insulin on renal sodium reabsorption, the sympathetic nervous system, the renin-angiotensin-aldosterone system, the transmembranous cation transport, the cardiovascular reactivity, the atrial natriuretic peptide and the kallikrein-kinin system, hyperinsulinaemia may contribute to the development of hypertension in these diseases. Preliminary evidence suggests that sensitivity to these possible blood-pressure-elevating action(s) of insulin is still present despite the resistance to the glucose-lowering action of the hormone. However, extrapolation of the epidemiological data and results of acute experiments indicate that the impact on blood pressure is rather small. The pathophysiological mechanisms of hypertension in the above-mentioned conditions are also not always consistent with insulin action(s). Moreover, some data suggest that insulin resistance, and not hyperinsulinaemia per se, underlies the blood pressure elevation, while the possibility cannot be excluded that both hypertension and insulin resistance are co-inherited, but unrelated, abnormalities.
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PMID:Insulin and blood pressure regulation. 204 23

The responsiveness of renin-angiotensin and kallikrein-kinin systems to furosemide challenge has been investigated in forty-six diabetic patients (34 NIDDM/12 IDDM), subdivided into Group I (uncomplicated DM), Group II (DM with hypertension), Group III (DM with nephropathy), Group IV (DM with hypertension and nephropathy) and a control group of 10 healthy volunteers. Plasma renin activity (PRA) was estimated by radioimmunoassay in blood samples drawn before and 10 min after furosemide administration (0.5 mg/kg i.v.). Urinary kallikrein levels were measured by bioassay using estrogenized rat uterus preparation in 4h urine samples collected before and after the diuretic. Urinary Na+ and K+ were also measured. The basal PRA in diabetics was not significantly different from controls, whereas, urinary kallikrein levels were markedly low in all patients. Both PRA and kallikrein levels increased after furosemide in controls while in diabetics this response was severely blunted. In a subset of Group I, a paradoxical fall in PRA and kallikrein levels was noted after furosemide, an effect similar to that observed in patients with nephropathy (Group III). This response in absence of clinical and biochemical parameters of nephropathy indicates early derangement of renal hemodynamic mechanisms heralding the onset of nephropathy.
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PMID:Plasma renin activity and urinary kallikrein excretion in response to intravenous furosemide in diabetic patients. 208 34

The kallikrein-kinin system of the blood serum (prekallikrein and kallikrein) was studied in 68 patients with chronic glomerulonephritis with the purpose of determining the significance of this system in the origin of proteinuria, protein content in the morning portion of urine and 24-hour portion. Linear correlation analysis revealed a direct relation of the levels of kallikrein and prekallikrein in the blood serum the morning and 24 losses of protein in patients suffering of glomerulonephritis with an isolated urinary syndrome (18 patients), nephrotic (27 patients) and glomerulonephritis with arterial hypertension.
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PMID:[THe role of the kallikrein-kinin system in the origin of proteinuria in glomerulonephritis]. 208 9

Eicosanoids, especially prostaglandins and other arachidonic acid metabolites, play an important role in gestosis. Experimental and clinical evidence suggest prostacyclin deficiency, enhanced platelet reactivity and increased production of thromboxane A2 as possible reasons for gestosis. In addition, pathological interactions between cyclooxygenase-derived products and the renin-angiotensin- and kallikrein-kinin systems may exist and contribute to hypertension and reduced fetoplacental blood flow. Moreover, pregnancy-induced hypertension appears to be also related to lipoxygenase products and enhanced lipid peroxidation. In general, little is known about the regulation of arachidonic acid metabolism in gestosis. It is also unknown whether altered activities of mediators and hormones are cause or effect of pregnancy-induced hypertension. This is particularly relevant to the site of eicosanoid formation, i.e. platelets, the trophoblast or endothelial cells. At this time, it is not possible to give therapeutical recommendations, which are specifically designed to correct changes in eicosanoid production in gestosis. Antihypertensive therapy alone is insufficient, particularly with regard to the fetal situation. Preventive treatment with low-dose acetylsalicylic acid may have a protective effect against pregnancy-induced hypertension. Presently, more selective antagonists of thromboxane generation and/or action are being developed and might provide fresh insights both into the pathology of the disease and improved drug treatment.
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PMID:[The significance of eicosanoids in gestosis]. 212 6


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