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

Chronic microcirculatory alterations produced by prolonged use of a vasoactive drug were repeatedly observed in the same skeletal muscle vessels of the dorsal microcirculatory chamber. Arterioles and venules with diameters averaging from 70 to 90 microns, the size range contributing most to peripheral vascular resistance, were measured daily for 6 days to determine differences in diameter, tortuosity, and number of branches. Hydralazine was given as a subcutaneous pellet (2.5 mg), with a release life of 21 days. Hydralazine caused a 39% dilation in arterioles of Wistar-Kyoto rats (WKY) at 3 hours but only an 8% dilation in those of spontaneously hypertensive rats (SHR). At 6 hours, arterioles in both groups were similarly dilated (30-33%). Beyond 6 hours, both SHR and WKY arterioles returned to their prehydralazine control diameter, even though arterial pressure was still reduced. By Day 6, in WKY, but not SHR, there was an increase in the tortuosity of arterioles and a tendency for an increase in their number. Venous diameter was also increased on Day 6, consistent with the fluid retention effect of hydralazine. These data indicate that some so-called vasodilators may cause long-term alterations in growth of vessels rather than an increase in vessel caliber.
Hypertension 1988 Jul
PMID:Long-term microvascular response to hydralazine in spontaneously hypertensive rats. 339 74

Isolated tail arteries from stroke-prone spontaneously hypertensive rats (SHRSP), but not normotensive Wistar-Kyoto (WKY) rats, exhibit oscillatory contractions in response to norepinephrine. To establish whether this vascular abnormality is secondary to elevated arterial pressure, SHRSP and WKY were treated with hydralazine and hydrochlorothiazide from weaning to 4 months of age. Hydralazine and hydrochlorothiazide treatment significantly attenuated hypertension development in SHRSP (systolic blood pressure: control SHRSP = 219 +/- 9 mmHg; treated SHRSP = 143 +/- 5 mmHg at 15 weeks of age). Helically-cut tail artery strips from all rats were mounted in tissue baths for isometric force recording and exposed to norepinephrine (6 x 10(-10)-6 x 10(-6) M) for 20 min at each concentration. Oscillatory activity was defined as the sum of the magnitudes of all phasic contractions occurring during the final 10 min of NE incubation. There was no significant difference in the magnitude of oscillatory activity between hydralazine/hydrochlorothiazide-treated SHRSP and control SHRSP. From these results we conclude that norepinephrine-induced oscillatory activity in SHRSP is a primary vascular abnormality that is not secondary to high blood pressure.
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PMID:Effect of antihypertensive therapy on a vascular change in genetically hypertensive rats. 343 74

Hydralazine is used as an antihypertensive vasodilator drug. A specific and sensitive method for extraction and analysis of hydralazine by high-performance liquid chromatography (HPLC) with electrochemical detection was developed. Hydralazine and 4-methylhydralazine (internal standard) in plasma were derivatized at room temperature with salicylaldehyde. The derivatives were extracted in basic medium with a mixture of heptane, methylene chloride and isopentyl alcohol. A very good separation of hydralazine and 4-methylhydralazine from matrix material was achieved on a Supelcosil LC-18-DB (5 microns) reversed-phase column kept at 28 degrees C with a mobile phase of 66% methanol in 0.055 M citric acid/0.02 M dibasic sodium phosphate (pH 2.5). The hydralazine level was measured electrochemically by a screen oxidation mode. This method offers significant advantages in sensitivity, specificity and accuracy. Sample analysis by HPLC required less than 8 min. Application of the method to monitor plasma levels of hydralazine from a patient receiving the drug for the treatment of severe pregnancy-induced hypertension is discussed.
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PMID:Determination of hydralazine in human plasma by high-performance liquid chromatography with electrochemical detection. 355 80

Hydralazine was administered short-term to 13 patients who had stable interstitial lung disease (ILD), pulmonary arterial hypertension (PAH); mean pulmonary arterial pressure ( [PAP]=26 +/- 9 mm Hg), and cor pulmonale (CP). All patients were studied at rest and during exercise. After intravenous hydralazine at rest, there were statistically significant increases in cardiac index (CI) (p less than 0.001), arterial oxygen saturation (SaO2) (p less than 0.01), and mixed venous saturation (S-vO2) (p less than 0.01). Pulmonary vascular resistance (Rp) (p less than 0.005) and systemic resistance (Rs) decreased (p less than 0.001), and PAP did not change. During exercise, PAP did not change; however, CI (p less than 0.01), PaO2 (p less than 0.001), and S-vO2 (p less than 0.01) increased further. The increase in Rp was significantly reduced (p less than 0.01). After continuation of oral hydralazine therapy in 12 patients for 7 days, PAP at rest was not statistically different from control; Rp and Rs remained decreased (p less than 0.001). The same results were found for CI, PaO2, S-vO2, and Rs during exercise. Although PAP did not change from control values, the drug significantly reduced the increase in Rp (p less than 0.005). Vasodilator therapy with hydralazine could be useful in patients with stable ILD who have inflammation with minimal to moderate fibrosis and PAH and might be used as an adjunct to conventional therapy for ILD and CP.
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PMID:Hemodynamic effect of hydralazine in interstitial lung disease patients with cor pulmonale. Immediate and short-term evaluation at rest and during exercise. 398 68

Ten milligrams nifedipine was administered orally to young and old persons with or without hypertension, and the acute effects of nifedipine on the renin-angiotensin-aldosterone system were studied one half to 3 hours later. Nifedipine reduced blood pressure and increased pulse rate in young and old persons with or without hypertension. Simultaneously, nifedipine produced a significant increase of plasma renin activity in young persons with or without hypertension but failed to do so in old persons with or without hypertension. As a result, angiotensin I and II increased significantly in young persons but not in old persons. Hydralazine elevated aldosterone concentration by stimulating the renin-angiotensin system but nifedipine failed to do so despite its effect on the renin-angiotensin system in young individuals. Since calcium is required to secrete aldosterone, it is suggested that nifedipine blocked aldosterone secretion by the agent's calcium antagonizing action.
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PMID:Acute effects of the calcium antagonist, nifedipine, on blood pressure, pulse rate, and the renin-angiotensin-aldosterone system in patients with essential hypertension. 629 95

A case of hepatic adenoma associated with oral contraceptive (OC) use in a 34-year old housewife is described. The patient presented with transient headaches which were experienced primarily on waking in the morning and were not alleviated with common analgesics. Hypertension was observed. Arteriographs of the kidneys were normal, but a hypervascularized zone in the liver was discovered. The patient, an emotional woman who habitually took sedatives for sleep, had used Neogynon OCs for 8 years. Most other findings were normal. The patient was treated with 20 mg Apresoline and 30 drops of Hydergina/day. After the suppression of the OCs, the patient's condition was favorable, with normal blood pressure of 120/80. The tumor was removed. Radiographic films and microscopic findings are reproduced. The tumor was clinically asymptomatic and was discovered by chance during an evaluation of hypertension. Until the intervention there was no hemoperitoneum. Because of the surgical intervention it was not possible to determine whether the tumor would have regressed after discontinuation of the OCs, as sometimes reported.
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PMID:[Hepatic adenoma caused by contraceptives. Presentation of a case]. 630 37

A total of 36 salt-depleted patients with suspected renovascular hypertension received intravenous hydralazine and 36 were subjected to the tourniquet test at the time of renal vein renin sampling. Simultaneous bilateral renal vein samples were obtained sequentially over 30 minutes. Both measures resulted in an increase in renin secretion. The number of patients showing a positive ratio (greater than or equal to 1.5) between the angiographically abnormal kidney and the contralateral kidney increased in both groups. In the hydralazine group, 47% had positive ratios at 0 min compared with 80% following hydralazine administration. In the tourniquet group, 53% had positive ratios at 0 min compared with 78% afterward. In neither group did all patients have positive ratios throughout the entire sampling period. Hydralazine produced a greater increase in renin, but more variable results. It is concluded that salt depletion is inadequate for detection of a pressor kidney, and an additional stress is required. Multiple simultaneous samples should be obtained.
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PMID:Hydralazine and the tourniquet test in renal vein renin sampling: a comparison. 633 55

Increased peripheral vascular resistance is the cause of elevated systemic blood pressure in most patients with long standing hypertension. The desired haemodynamic effect in antihypertensive therapy is dilation of the constricted arterioles by a drug that acts directly on the vascular smooth muscle while not affecting the heart or the venous return. Hydralazine, diazoxide and minoxidil act directly on vascular smooth muscle to produce vasodilatation and have been used with variable degrees of success in the long term treatment of hypertension. Their cellular mechanism of dilation is not understood fully, but the ability to chelate certain trace metals required for smooth muscle contraction has been proposed as a possible mechanism of action for these drugs. The calcium antagonists (calcium entry blocking drugs) are a distinct group of compounds that interfere with the normal transmembrane flux of extracellular calcium ions on which vascular tissue depends for contraction or impulse generation. Thus, calcium anti-agonists can reduce the contractile activity of the heart, and promote coronary and systemic vasodilatation. These effects provide the clinical rationale for the use of calcium antagonists in the management of ischaemic heart disease and hypertrophic cardiomyopathy. Since systemic vasodilatation can be expected to reduce elevated arterial blood pressure, interest has focused recently on calcium antagonists in the medical management of systemic hypertension. All the calcium antagonists are able, in low concentrations, to relax the smooth muscle vasculature from coronary, cerebral, mesenteric, and renal arteries. The effects on the myocardium, cardiac impulse tissue, and vascular smooth muscle are different in magnitude, however, depending on the individual agent that is used. Clinical experience in the treatment of hypertension with this class of agents is confined to verapamil, nifedipine, and diltiazem. In this article, the scientific rationale for using calcium antagonists in the treatment of arterial hypertension is explored and the clinical experiences with the different calcium antagonists used in hypertension are reviewed.
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PMID:Calcium antagonists. Clinical use in the treatment of systemic hypertension. 633 98

Despite the short plasma half-life of hydralazine, once daily Slow Apresoline has been shown to maintain blood pressure control in well controlled hypertension. In the present investigation of 118 inadequately controlled hypertensives, we have shown that 50-150 mg Slow Apresoline once daily induces a significant blood pressure reduction and is well tolerated. Normotension, i.e. supine diastolic blood pressure less than 95 mmHg, was reached in 53% of the patients. Normotension or a supine diastolic blood pressure reduction of greater than or equal to 10 mmHg was achieved in 72% of the patients, the hydralazine responders. Sixteen patients discontinued treatment due to symptoms probably related to hydralazine. Acetylator phenotyping showed that slow acetylators predominated in the group of patients discontinuing hydralazine due to side-effects. In contrast, 90% of the phenotyped non-responders were rapid acetylators, which suggests a suboptimal use of hydralazine in some rapid acetylators.
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PMID:Evaluation of once daily hydralazine in inadequately controlled hypertension. 636 41

Renal venous renin (RVR) studies were done in 34 patients with moderate-to-severe hypertension before (unstimulated) and after (15- and 30-minute samples) a 20-mg bolus of i.v. hydralazine. The unstimulated lateralizing ratio of angiographically abnormal kidney or ipsilateral (I) to contralateral (C) RVR of greater than or equal to 1.5 was found in 69%, and the unstimulated ratio of I-inferior vena cava (IVC) renin below renal veins (I-IVC)/IVC (index of reduced renal blood flow) of greater than or equal to 0.48 was present in 50% of 16 patients (10 unilateral and 6 bilateral renal artery stenosis). The I/C and I-IVC/IVC ratios were abnormal in 100% and 88%, respectively, in 1 or both of the posthydralazine sampling in these patients. Hydralazine increased the absolute RVR from the ischemic kidney more than the contralateral kidney and did not result in new false-negative or positive I/C ratios. It is concluded that hydralazine stimulation of RVR is a safe and reliable way to determine the functionally significant pressor kidney in renovascular hypertension.
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PMID:Enhancement of renal venous renin ratios by intravenous hydralazine in renovascular hypertension. 636 84


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