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

There is evidence that atrial natriuretic factor (ANF) has an action in the inner medullary collecting duct. In addition, the prehypertensive Dahl salt-sensitive (S) rat has an intrinsic tendency toward less natriuresis than the Dahl salt-resistant (R) rat has when challenged with ANF. To test the hypothesis that renal papillary collecting tubule cells from prehypertensive S rats might be genetically less responsive to ANF, S and R cells were grown in culture and studied for responsiveness to ANF by measurement of cyclic nucleotide responses. There was a concentration-dependent effect of ANF on renal papillary collecting tubule cell synthesis of intracellular cyclic guanosine 3',5'-monophosphate (cGMP) in both strains. However, the S cells were hyporesponsive compared with the R cells (p less than 0.002, by analysis of variance). Likewise, in response to Na nitroprusside, the S cells were hyporesponsive compared with the R cells as measured by intracellular cGMP accumulation (p less than 0.03, by analysis of variance). Arginine vasopressin stimulated intracellular cAMP equally in both strains. Also, ANF equally enhanced intracellular cGMP in glomerular mesangial cells from S and R rats, indicating possible specificity of the reduced responsiveness to ANF to the distal nephron of S rats. Plasma ANF levels had a slight tendency to be higher in prehypertensive S rats than in R rats (p = 0.088, by t test). These results suggest that the papillary collecting duct of Dahl S and R rats may differ in guanylate cyclase activity. This difference may partially explain the impaired natriuretic responses of S rats and could represent a factor contributing to the development of salt-sensitive hypertension.
Hypertension 1987 Jul
PMID:Papillary collecting tubule responsiveness to atrial natriuretic factor in Dahl rats. 303

Elevated levels of a specific renal growth factor, renotropin, have been associated with spontaneous hypertension. To examine this association more closely, we have undertaken the development of a better assay system to characterize and purify renotropin. Sera from rabbits prior to operation (control) and at a specified time after unilateral nephrectomy (uni) were examined for renotropic activity. Comparing the effects of uni to control sera in the same rabbit, significant stimulation of 3H-thymidine incorporation into the DNA of primary rabbit kidney cultures incubated in D-valine medium to eliminate fibroblast growth was noted: at 3 days postoperatively 73% (n = 13), at 7 days 103% (n = 39), at 10 days 130% (n = 31), at 21 days 101% (n = 24), at 42 days 89% (n = 13). All values were at least P less than 0.01. The stimulatory properties were dose-dependent but reached a plateau at high serum concentrations. Comparing CPM/mg protein in uni/control in different concentrations of sera 7 days postoperatively, uni versus control were 67/44 at 5% v/v, 139/72 at 10% v/v, 261/161 at 20% v/v, and 243/136 at 40% v/v. The renotropic effect of uni sera remained after dialysis in incubation medium and after sera were heated in boiling water for 5 minutes. Renal extracts obtained from growing kidneys 7 days postnephrectomy augmented renotropic activity. Atrial natriuretic factor, ouabain, PGF2 alpha, PGE1, and cAMP did not possess renotropic activity. We conclude that the primary rabbit kidney culture assay for renotropin is highly sensitive and will be an important tool to comprehend the role of renotropin in the pathogenesis of hypertension.
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PMID:The rabbit renotropic system. 340 54

The physiological significance of sulfoconjugated catecholamines and their involvement in clinical disorders, e.g. hypertension and Parkinsonism, is poorly investigated. For this reason, the sulfoconjugated isomers of dopamine as well as of norepinephrine were synthesized by modified methods. All isomers and their intermediates could be detected by a reversed-phase high-performance liquid chromatography with ultraviolet detection (HPLC-UV) with short retention times and a good reproducibility. Ion-exchange chromatography with an extended column length improved the separation of the reaction products, and the immediate control by HPLC-UV enabled precise cutting of the fractions. The selection of the fractions with the optimum ratios of product/by-product resulted in improved yields and highest purity. All by-products, e.g. dopamine sulfonic acids, were less than 0.04%, as detected by HPLC-UV and, in addition, the contamination by free catecholamines was only 41 x 10(-4)-87 x 10(-4)%, as measured by HPLC with electrochemical detection (HPLC-ED). The purity was further demonstrated in two highly sensitive biological assays: cAMP production in human mononuclear leukocytes and aggregation of human platelets. The sulfoconjugated catecholamines were characterized by melting point, thin-layer chromatography, infrared spectrum, HPLC-UV, elemental analysis, and unequivocally identified by 1H-NMR.
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PMID:Syntheses of the sulfoconjugated isomers of norepinephrine and dopamine, controlled by HPLC with ultraviolet detection. 341 78

In the aortas and mesenteric arteries from spontaneous hypertensive rats and in the aortas from stress- and desoxycorticosterone-acetate-hypertensive rats, the intracellular cGMP: cAMP ratios were significantly elevated when compared to the ratios in the aortas of the respective controls. Decreases in the intracellular cAMP or cGMP levels were consistently associated with increased activity of the cyclic-nucleotide-specific low K(m) phosphodiesterase (3':5'-cAMP 5' nucleotidohydrolase, EC 3.1.4.17). Increases in intracellular cGMP levels were associated with elevated guanylyl cyclase [GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2] activity. Furthermore, adenylyl cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] activity was less sensitive to stimulation by the beta-adrenergic stimulant isoproterenol in both the aortas and the hearts of the hypertensive animals. These changes could provide the biochemical basis for the (a) increased vascular smooth muscle tone and peripheral resistance observed in these animals, (b) increased reactivity to norepinephrine, and (c) decreased ability of aortas from hypertensive rats to relax. The presence of these same effects in different etiologic types of hypertension indicates that this aberration in cyclic nucleotide metabolism may represent a common metabolic defect basic to the hypertensive syndrome irrespective of etiology.
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PMID:Aberrations of cyclic nucleotide metabolism in the hearts and vessels of hypertensive rats. 415 74

Labile hypertension is often associated with elevated cardiac output, increased plasma renin activity (PRA) and urinary cyclic AMP excretion in response to upright posture and to isoproterenol. The beta-blocking agent propranolol was demonstrated to be an effective therapeutic agent in this condition. The effect of posture on cyclic AMP, PRA, pulse rate and blood pressure was therefore studied during the administration of propranolol and a placebo in patients with labile hypertension. With the patient on placebo, upright posture induced an increase in pulse rate, cyclic AMP excretion and PRA. Propranolol administration decreased the recumbent and upright blood pressures, pulse rate and PRA. Cyclic AMP excretion remained unchanged in the recumbent position but the postural increase was abolished. No appreciable changes in catecholamine excretion occurred during propranolol administration. Propranolol normalizes some humoral as well as hemodynamic abnormalities of labile hypertension and therefore may be of benefit in long-term treatment and possibly also in the prevention of stable hypertension.
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PMID:Effect of propranolol on cyclic AMP excretion and plasma renin activity in labile essentrial hypertension. 435 22

Restriction of motor activity and motor-alimentary conditioning in dogs reduced the adrenaline (A) and noradrenaline (NA) contents in the myocardium, dopamine, too, revealing a tendency to reduction. Basal activity of the sarcolemma adenylate cyclase (AC), its sensitivity to A, NA and NaF did not change as well as the basal activity of sarcolemma phosphodiesterase (PDE) and its sensitivity to the inhibitory effect of high concentrations of Ca2 (10(-4) M). In experimental informational neurosis, NA content in the myocardium increased 5-fold compared to control values, the dopamine content also increasing. Basal activity of the sarcolemma AC did not change whereas its sensitivity to NA and to activating effect of NaF decreased. Basal activity of PDE increased and its sensitivity to Ca2 effect decreased in this condition. The increase of PDE activity and increase of its sensitivity to the inhibitory effect of high concentrations of Ca2+ in combination with desensitization of the regulatory subunit AC to NA followed by changes in its catalytic subunit, seem to lead to a decrease of cAMP content and cAMP-dependent phosphorylation in cardiomyocyte that may underlie the Ca2+ transport disturbance observed in informational neurosis, and reduction of contractility of the contractile protein system. Heart pressure overload, caused in informational neurosis by the stable arterial hypertension may play an important role in the genesis of this reduction.
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PMID:[Catecholamine concentration and adenyl cyclase and phosphodiesterase activities of the sarcolemma of myocardial cells during hypokinesia and in experimental information neuroses]. 609 71

The effect of road noise on blood catecholamines, cAMP and certain cardiovascular and metabolic parameters was studied in a group of young untreated essential hypertensives. It was found that the 10' stimulus increased both systolic and diastolic pressure values. Blood catecholamines rose only after 5'. The most significant increase was in adrenaline as opposed to noradrenaline and dopamine. Significant changes were noted in cAMP and triacylglycerols (10' and 15' after commencement of the stimulus respectively). Comparison with previous results in normotensives suggested that the catecholamine response to stress is primarily alpha-receptorial when blood pressure is normal and beta-adrenergic in hypertension.
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PMID:[Effect of street noise on blood catecholamines, cyclic AMP and various cardiovascular and metabolic functions in a group of subjects with untreated essential hypertension]. 609 40

Cadmium (Cd) produces injurious effects on reproductive function and has been implicated in the pathogeneses of hypertension. The present article summarizes available data on alterations in the cyclic AMP system of testicular and prostatic tissue as well as in catecholamine metabolism in adrenal glands following exposure to Cd and subsequent withdrawal. Daily Cd (1 mg/kg IP) for 45 days decreased prostatic and testicular weights of mature male rats. In prostate, chronic treatment with Cd reduced cyclic AMP levels to 57% of normal values which appeared to be due to the decrease in adenylate cyclase activity since cyclic AMP metabolism by phosphodiesterase was not significantly altered. Cyclic AMP binding to prostatic protein kinase was increased following Cd administration as was the activity of the cyclic AMP-dependent form of protein kinase. In contrast to the prostate, testicular adenylate cyclase was stimulated by Cd treatment. However, the endogenous cyclic AMP levels remained unaffected since the increase in testicular adenylate cyclase was offset by a concomitant increase in the activity of phosphodiesterase. Although the activities of the cyclic AMP-dependent and the independent forms of testicular protein kinase were significantly depressed, the binding of cyclic AMP to protein kinase from testes of Cd-treated rats was not affected. Discontinuation of treatment for 28 days in rats that had previously been given the heavy metal for 45 days resulted in at least a partial reversal of several of the cadmium-induced changes in cyclic AMP metabolism of the rat prostate and testes. However, the weight of the prostate glands remained essentially in the same range as that seen in the "treated group."Data suggest that cyclic AMP metabolism in both the primary and the secondary reproductive organs is altered following chronic Cd treatment and that some changes persist even 28 days following the termination of daily exposure to the heavy metal.Cd treatment also increased adrenal weights and augmented the levels of adrenal norepinephrine and epinephrine as well as the activity of tyrosine hydroxylase. Discontinuation of the heavy metal treatment for 28 days, in rats previously injected with Cd for 45 days, restored the activity of tyrosine hydroxylase as well as the amount of norepinephrine and epinephrine. In contrast, adrenal weights were restored only partially following withdrawal of Cd treatment. Evidence indicates that the changes in adrenal catecholamine metabolism may be the result of stress induced by chronic exposure to this heavy metal. In addition, some of the untoward effects such as hyperglycemia and arterial hypertension seen during Cd toxicity might be related to increased synthesis of epinephrine in adrenal glands.
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PMID:Testicular cyclic nucleotide and adrenal catecholamine metabolism following chronic exposure to cadmium. 611 36

Distinct differences in central and peripheral noradrenaline (NA) were observed in the hypertension prone (SBH) and resistant (SBN) strain, derived from the Hebrew University SABRA rats. In the medulla oblongata NA concentration was 90% higher and tyrosine hydroxylase activity 88% lower in SBN when compared to SBH, suggesting marked strain differences in NA turnover. In this area, NA-induced cAMP generation was higher in SBH than in SBN, while the hypothalamus, the reverse situation was present. The relevance of hypertension of the reciprocal cAMP changes is still uncertain. The concentration of NA in heart tissue was significantly higher in SBN than in SBH. Doca-salt treatment caused hypertension and depletion of atrial NA in SBH, but had no effect on either blood pressure or atrial NA in SBN rats. The results suggest that resistance to hypertension in SBN rats is associated with decreased NA turnover in medulla oblongata and reduced activity of cardiac neuronal sympathetic endings.
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PMID:Distinguishing traits in the Sabra hypertension-prone (SBH) and hypertension-resistant (SBN) rats. 611 32

By selective inbreeding of the Hebrew University Sabra rat, we have obtained a hypertension prone (H) and a hypertension resistant (N) substrain. The criteria for selection was the blood pressure response to DOCA-salt. The outstanding element of our model is the N rat with its remarkable resistance to hypertension. When compared to H, the N rat presents the following characteristics: 1. The blood pressure of experimentally naive N rats is significantly lower at comparable ages, in both sexes. 2. N rats are resistant to both DOCA-salt and renal clip hypertension. 3. In the medulla oblongata (MO) of N rats, the noradrenaline (NA) content is significantly higher and the activity of tyrosine hydroxylase is significantly lower. 4. In the MO of N rats, the sensitivity of the NA dependent cAMP generating system is significantly decreased. 5. In the atrium of N rats, the NA content is significantly higher, and is unaffected by DOCA-salt treatment. The results suggest that genetic differences in catecholamine metabolism may account for the disparate susceptibility to hypertension of the two strains.
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PMID:The Sabra hypertension prone (H) and hypertension resistant (N) rat strain. 612 Apr 96


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