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

We have developed a system for measuring the dynamic changes in the cytoplasmic free calcium concentration [( Ca2+]i) in single vascular smooth muscle cells (VSMC) that is highly sensitive and does not cause cellular damage. Marked increases in [Ca2+]i in response to stimulation with caffeine and angiotensin II occurred in some VSMC of 4-week-old spontaneously hypertensive rats (SHR), in which the blood pressure and basal [Ca2+]i levels are not yet elevated. In 8-week-old rats, the basal [Ca2+]i level in VSMC was higher in SHR than in Wistar-Kyoto rats. Although the effects of high blood pressure on [Ca2+]i in vivo were expected to disappear during the passage culture, the [Ca2+]i in the fifth-passage cells was similar to that in the primary cells. These results suggest that the maintenance of high [Ca2+]i levels in VSMC of SHR is genetically regulated and is one of the mechanisms of hypertension in this strain, and that abnormal calcium regulation in VSMC of SHR is expressed even before overt hypertension.
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PMID:Abnormal calcium handling in vascular smooth muscle cells of spontaneously hypertensive rats. 216 Apr 94

Earlier work with rat arteries has resulted in a widely held assumption that resistance artery smooth muscle will not contract on exposure to a reduced transplasmalemmal sodium gradient. In view of the well-recognized low sensitivity of rat tissue to cardiac glycosides, we have investigated the effects of altering the transplasmalemmal sodium gradient on vascular smooth muscle tone by using human resistance arteries. Incubation of arteries in low sodium or in ouabain to inhibit active sodium efflux for 1 hour increased the contractile response to caffeine stimulation; this finding indicated enhanced calcium buffering by the sarcoplasmic reticulum. Prolonged incubation in ouabain in the presence of phentolamine or diltiazem resulted in a concentration-dependent increase in the tone of resting human resistance arteries. Reduction of the transplasmalemmal sodium gradient by incubation in low sodium buffer effected an increase in tone similar to that obtained in the presence of ouabain. These results suggest that alteration of the transplasmalemmal sodium gradient may increase the vascular smooth muscle tone of human resistance arteries by altering intracellular calcium handling. This is a new finding in human resistance arteries and may involve inhibition and, indeed, reversal of sodium-dependent calcium efflux. A concentration-dependent potentiation of tone was found after the addition of ouabain to submaximally activated arteries. Sodium-calcium exchange may also play a pivotal role in this mechanism.
Hypertension 1990 Jun
PMID:Effects of ouabain and low sodium on contractility of human resistance arteries. 216 5

Many drugs have been used in treating patients with postural hypotension but for a large number the evidence of benefit is small and the potential for adverse effects, particularly supine hypertension, is great. Full clinical assessment is essential at the outset to define the nature and extent of pathophysiological disturbance of autonomic function. Many patients can be treated adequately by sleeping with the head of the bed elevated, and the use of fludrocortisone. Patients without evidence of central neurological deficit may benefit from additional treatment with drugs which alter beta-adrenoceptor tone. Patients who respond poorly to these measures should be admitted to hospital, and treatment with desmopressin initiated. Symptomatic postprandial hypotension should be identified early since the response to these measures alone is often poor, caffeine administered before eating, with abstinence for the rest of the day, may be very helpful.
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PMID:Treatment of postural hypotension. A review. 217 15

The diagnosis of mild hypertension and the treatment of hypertension require accurate measurement of blood pressure. Blood pressure readings are altered by various factors that influence the patient, the techniques used and the accuracy of the sphygmomanometer. The variability of readings can be reduced if informed patients prepare in advance by emptying their bladder and bowel, by avoiding over-the-counter vasoactive drugs the day of measurement and by avoiding exposure to cold, caffeine consumption, smoking and physical exertion within half an hour before measurement. The use of standardized techniques to measure blood pressure will help to avoid large systematic errors. Poor technique can account for differences in readings of more than 15 mm Hg and ultimately misdiagnosis. Most of the recommended procedures are simple and, when routinely incorporated into clinical practice, require little additional time. The equipment must be appropriate and in good condition. Physicians should have a suitable selection of cuff sizes readily available; the use of the correct cuff size is essential to minimize systematic errors in blood pressure measurement. Semiannual calibration of aneroid sphygmomanometers and annual inspection of mercury sphygmomanometers and blood pressure cuffs are recommended. We review the methods recommended for measuring blood pressure and discuss the factors known to produce large differences in blood pressure readings.
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PMID:Accurate, reproducible measurement of blood pressure. 219 91

Recently it has been shown that, after a meal, blood pressure may fall in the elderly, in patients with autonomic failure and in patients on haemodialysis. This review deals with the available data on postprandial blood pressure reduction, the clinical significance and some pathophysiological hypotheses. The mechanism is not fully understood, but postprandial blood pressure reduction seems to be related to glucose related factors, since blood pressure only falls after oral glucose loading, but not after oral fructose, fat or protein loading. Vasoactive gastrointestinal peptides may play a role in the glucose induced vasodilation of splanchnic vasculature, but attempts to identify such peptides have been unsuccessful. The role of insulin in postprandial blood pressure reduction remains to be elucidated, but it does not appear to have any influence on systemic vasodilation or baroreflex response. Although the clinical significance of postprandial blood pressure reduction remains uncertain, patients can be advised in several ways on how to avoid this symptom. Treatment of hypertension, small carbohydrate meals, caffeine and treatment with the somatostatin analogue SMS 201-995 may have a beneficial effect. Patients on haemodialysis with symptomatic hypotension should not consume meals during the procedure.
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PMID:Postprandial blood pressure reduction. 221 39

We surveyed phenylpropanolamine (PPA) use and overuse among 309 diet center clients. Fifty-one percent of all subjects surveyed reported using PPA drugs: 44 percent used cold medicines and 16 percent used diet aids. Twenty-two percent of diet aid users and 7 percent of cold medicine users reported that they deliberately used more than the dosage recommended to improve efficacy. Among diet aid users, 59 percent also regularly consumed caffeine. Despite package warnings, individuals who had been told by their doctors that they were hypertensive used PPA products as often as normotensive individuals. PPA, the fifth most frequently used drug in the USA, is contained in over-the-counter (OTC) diet aids as well as OTC and prescription cold medicines. Severe adverse drug reactions (ADRs) including hypertensive crisis, stroke and death have been attributed to PPA products. Clinical studies have shown that using greater than recommended doses of PPA and using PPA in combination with caffeine may increase the risk of ADRs. Overweight patients may be particularly at risk for ADRs to PPA because they are likely to be hypertensive and to use diet aids. We recommend informing diet center clients of the potential dangers of consuming PPA products, especially more than the recommended dose, in the presence of hypertension, and when other sympathomimetic drugs are being taken.
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PMID:Phenylpropanolamine and caffeine use among diet center clients. 222 92

The effects of oral contraceptives (OCs) on drug therapy are related mainly to the inhibition of microsomal oxidation as well as the induction of enzymes involved in conjugation reactions. Since many drugs share these catabolic pathways, their pharmacodynamics will be affected by OCs. Notable interactions include an increased bioavailability of analgesics, tranquilizers, and tricyclic antidepressants. OCs increase the risk for hypertension, and pharmacokinetic interactions are to be expected when OCs are administered with antihypertensive drugs. Likewise, OCs affect lipid metabolism and thus modify the effects of atherogenic drugs; however, the different forms of hyperlipidemia show a heterogeneous response to OCs. Another particular concern is that the gestagen components of OCs may cause peripheral insulin resistance and may require dose adaption with antidiabetic treatments. Two common nonprescription drugs, theophylline and caffeine, show decreased clearance rates due to OCs. All share a common oxidation pathway involving cytochrome P-450 and P-448. However, cigarette smoking stimulates these enzymes, and the decreased clearance of theophylline and caffeine is usually not observed in smokers. The reports of effects of OCs and alcohol taken together are mixed, and no clinically relevant conclusions can be drawn. Most vitamin and mineral levels are influenced by OCs, but this is a concern only under conditions of deprived diet, when normal dietary adjustments are impossible. An important caveat of the many documented effects of OCs on the pharmacodynamics of other drugs is that, in most instances, these effects will be counterbalanced with kinetic changes and result in no clinical manifestation. Nevertheless, clinicians must be aware of possible adverse reactions, particularly in predisposed patients.
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PMID:Influence of oral contraceptives on drug therapy. 225 28

Weight reduction, alcohol restriction, mild salt restriction, eating a vegetarian diet and increasing aerobic exercise will generally lower the blood pressure in patients with essential hypertension. Eating a diet rich in potassium and reducing caffeine intake may also be helpful in reducing the pressure, but increasing the fiber or calcium intake will generally be ineffective. Reducing fat intake from the usual 40% of total calories to 25-30% may reduce hypertension directly or by weight reduction. Smoking, when combined with excessive caffeine or alcohol intake may have an additive effect on blood pressure. Monotherapy with such behavioral techniques as self-monitoring of blood pressure, biofeedback, meditation, yoga, progressive muscular relaxation or cognitive therapy may reduce the blood pressure to a variable degree, and combinations of these treatments may be even more successful.
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PMID:Non-pharmacological treatment of hypertension. 225 79

Hypertension which is resistant to treatment carries a relatively bad prognosis. Factors associated with treatment resistance were examined in a case-control study in a hospital hypertension clinic. Patients with resistant hypertension had more severe hypertension and more frequently had evidence of end-organ damage on presentation to the clinic. The prevalence of accelerated phase hypertension, renovascular disease and impaired renal function was also higher in these patients. Cigarette smoking, and the combination of cigarette smoking and heavy caffeine use, were greater in patients with resistant hypertension. Resistant hypertension did not appear to be associated with older age, obesity, regular alcohol use, various psychological factors or non-compliance. These findings support an aggressive investigation policy in resistant hypertension, and underline the harmful effects of cigarette smoking to hypertensive subjects.
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PMID:Factors related to treatment resistance in hypertension. 227 60

In experimental studies, caffeine increases blood pressure in caffeine-naive or nontolerant individuals, but not in regular caffeine consumers. Using an epidemiologic approach, we examined the hypothesis that serum-caffeine concentration would be positively associated with blood pressure in infrequent (but not habitual) caffeine users in a group of bus drivers. Infrequent and habitual users of caffeine showed no differences in systolic or diastolic blood pressures when there is no measurable caffeine in the serum. However, at serum concentrations of caffeine typical of those achieved after one to two cups of coffee, infrequent users demonstrated greater systolic and diastolic pressures, averaging +5.3 mm Hg and +3.6 mm Hg, respectively, compared with habitual users. The magnitude of difference remained after adjustment for age, body mass index, race, sex, and tobacco and alcohol use. These elevations are large enough to exaggerate the prevalence of hypertension, if such assessments are based on cross-sectional surveys that fail to assess both proximate caffeine consumption and usual caffeine consumption habits.
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PMID:Pharmacoepidemiology of the effect of caffeine on blood pressure. 229 20


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