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

To examine the intracellular calcium content of the vascular smooth muscle in the chronic phase of renovascular hypertension, the effects of caffeine on isolated aortic, renal and iliac arterial strips were evaluated in two-kidney, one-clip renovascular hypertension in rabbits. 10 weeks after left renal artery constriction in the constricted group, systemic blood pressure (BP) was significantly higher than in the control group, but plasma renin activity was similar to the control value. The amplitude of caffeine-induced contraction of various vascular strips in the constricted group gradually increased and, at 10 weeks, this was higher in the constricted group than in the control group. In the constricted group, sodium loading produced BP elevation and increased the amplitude of caffeine-induced contraction, whereas sodium constriction decreased BP and the amplitude. In the control group, altered sodium intake did not affect BP and the amplitude of caffeine-induced contraction. These results suggest that in the chronic phase of renovascular hypertension, the increased caffeine-sensitive intracellular calcium store on vascular smooth muscle, which is increased by sodium loading and is decreased by sodium restriction, may contribute to the maintenance of hypertension.
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PMID:Effects of caffeine on the vascular smooth muscles isolated from two-kidney, one-clip renovascular hypertension in rabbits. 274 28

Dietary alteration or intervention is an ideal method of preventing or treating hypertension. Medication may be eliminated or reduced in many cases. Correction of obesity and alcohol abuse are confirmed methods of treating hypertension. Reduction of sodium intake is effective in that portion of the population which is salt-sensitive. Probably, the ratio of sodium to potassium is of importance and increasing potassium intake while reducing sodium intake is effective in many situations. Evidence is being reported which indicates that adequate intake of calcium, and perhaps magnesium, is effective in preventing hypertension. Limited information indicates that a sufficiency of dietary essential fatty acids and fibre are effective in hypertension prevention. The role of dietary protein, carbohydrates, fat, cholesterol, vitamins, and essential elements (other than those mentioned above) in the pathogenesis has not been fully elucidated at this time, but there are indications that adequate intakes are beneficial in hypertension. Water hardness may have some effect in reducing hypertension incidence, and any effectiveness would probably result from calcium and magnesium in the drinking water. Animal studies and limited human studies indicate some detrimental effects of heavy metals, such as lead and cadmium, upon the pathogenesis of hypertension. Information regarding caffeine intake is inconclusive.
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PMID:Dietary factors in essential hypertension. 300 94

The purpose of this study was to determine whether or not caffeine would exacerbate renovascular hypertension. Therefore, we examined the effects of chronic caffeine administration on arterial blood pressure in rats subjected to either unilateral renal artery clipping (2K-1C rats) or sham-operation. Animals in each group were randomly assigned to receive either 0.1% caffeine in their drinking water or normal drinking water, and systolic blood pressure was monitored for 6 wk. Caffeine markedly exacerbated the severity of hypertension in 2K-1C rats and caused histological changes consistent with malignant hypertension. 6 wk after surgery, systolic blood pressure, plasma renin activity, and creatinine clearance in control 2K-1C rats were 169 +/- 5 mmHg (mean +/- SEM), 4.4 +/- 0.5 ng AI X ml-1 X h-1, and 2.9 +/- 0.2 ml/min, respectively; as compared with 219 +/- 4 mmHg, 31.8 +/- 7.8 ng AI X ml-1 X h-1, and 1.4 +/- 0.3 ml/min, respectively, in 2K-1C rats receiving caffeine (all values were significantly different compared with control 2K-1C). Chronic caffeine administration did not alter systolic blood pressure, plasma renin activity, or creatinine clearance in sham-operated rats or spontaneously hypertensive rats. Chronic treatment with enalapril (a converting enzyme inhibitor) prevented the development of hypertension in control 2K-1C rats and caffeine-treated 2K-1C rats; however, withdrawal of enalapril precipitated a rapid rise in systolic blood pressure in caffeine-treated 2K-1C rats, but not in control 2K-1C rats. These experiments indicate that caffeine specifically exacerbates experimental renovascular hypertension and might worsen the hypertensive process in patients with renovascular hypertension.
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PMID:Chronic caffeine administration exacerbates renovascular, but not genetic, hypertension in rats. 302 89

Diet clearly influences neurotransmission. This can be important in grossly undernourished children. It can also be important in children in whom normal homeostatic mechanisms governing food intake are bypassed. Subtle differences in behavior can occur with physiologic variation in food intake. Components of foods can also be used as drugs. Starvation can impair neuronal maturation and can have lasting effects upon behavior and intellectual performance. The extent of starvation's impact upon the brain depends upon whether undernutrition occurred during a critical phase in brain development. Short-term fasting has small, but significant, effects upon intellectual performance. Even when gross malnutrition is not present, subtle changes in diet may modulate brain function. Tryptophan, tyrosine, and choline in the diet are used as precursors for neuronal synthesis of serotonin, dopamine and norepinephrine, and acetylcholine, respectively. It is likely that the brain's sensitivity to certain components of the diet exists to permit monitoring of food intake by the central nervous system. Tryptophan, tyrosine, and choline may be useful in treatment of humans with sleep disorders, pain depression, mania, hypertension, shock, or dyskinesias. Other components of the diet that may affect behavior include food additives, sugar, and caffeine. Food additives may exacerbate hyperactive symptoms in a small proportion of children with attention deficit disorder. Given that there is little potential for harm and that there is a subpopulation that may respond, a trial of a diet that contains no food additives may be a valid diagnostic approach for children with attention deficit disorder who do not respond to stimulant therapy or for children for whom stimulant therapy is not desired. Refined sugar has been blamed for many behavioral abnormalities. Subtle effects of carbohydrate upon behavior have been reported, but the existing data do not support the hypothesis that sucrose or fructose exert special effects upon neurotransmission. Caffeine is easily detected as a stimulant by humans, but it has little effect upon cognitive function. Administration of large doses of vitamins has no beneficial effect in most humans with schizophrenia, attention deficit disorder, autism, Down's syndrome, or drug addiction. Large doses of niacinamide may even be harmful, as they may cause hepatic damage.
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PMID:Dietary influences on neurotransmission. 302 51

The effect of caffeine consumption on mortality was evaluated in a historical cohort study of 10,064 diagnosed hypertensive individuals participating in the Hypertension Detection and Follow-up Program from 1973 to 1979. Total caffeine intake level from beverages (coffee and tea) and certain medications, was estimated at the 1-year visit. No evidence was found supporting an association between increased level of caffeine consumption and increased all-cause mortality or cardiovascular disease mortality during the following 4 years. Cigarette smoking was significantly associated with mortality; the association being more pronounced among non- and low-caffeine consumers for all-cause mortality and among non-caffeine consumers for all cardiovascular mortality except cerebrovascular mortality.
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PMID:Mortality patterns among hypertensives by reported level of caffeine consumption. 304 18

Our previous studies support the hypothesis that activation of the renin-angiotensin system by renal ischemia elevates adenosine levels and that adenosine acts in a negative feedback loop to limit renin release and to mitigate some of the hypertension-producing effects of angiotensin II. To further test this hypothesis, we compared the time course of caffeine-induced increases in plasma renin activity with the time course of changes in plasma levels of adenosine in two models of renin-dependent renovascular hypertension. Also, we compared the effects of caffeine on plasma renin activity and arterial blood pressure in renin-dependent versus renin-independent renovascular hypertension. In comparison to sham-operated rats, plasma levels of adenosine in the left and right renal veins and aorta were elevated severalfold in two-kidney, one clip rats (2K1C) 1 week after left renal artery clipping. However, adenosine levels declined during the second and third weeks after clipping. In 2K1C rats treated chronically with caffeine, plasma renin activity was markedly elevated during the first week after operation as compared to non-caffeine-treated 2K1C rats. However, during the second and third weeks after clipping, caffeine had lesser effects on plasma renin activity. A temporal relationship between plasma adenosine levels and caffeine-induced hyperreninemia was also observed in rats with aortic ligation. Caffeine accelerated hypertension in 2K1C rats and rats with aortic ligation (renin-dependent renovascular hypertension), but it had no effect on plasma renin activity or blood pressure in one-kidney, one clip rats (renin-independent renovascular hypertension). These results lend further support to the hypothesis that adenosine functions to mitigate the renin-angiotensin system in renin-dependent renovascular hypertension.
Hypertension 1988 Aug
PMID:Adenosine in renin-dependent renovascular hypertension. 304 93

Heroin, cocaine, amphetamines, sympathomimetic drugs can cause cerebral angiopathy. We report 2 patients with cerebrovascular disorders after ingestion of a nasal vasoconstrictor containing phenylpropanolamine (P.P.A.). The first patient had two acute repetitive attacks of severe headache and vomiting, occurring after a daily treatment with 180 mg of P.P.A. during 6 weeks. The second patient had an intracerebral hemorrhage, occurring some hours after taking for the first time 120 mg of P.P.A. In both cases, cerebral angiography, performed in the next week, demonstrated segmental narrowing and dilatations of medium-size intracranial arteries. None of the usual causes of cerebral vasculitis were present. The outcome was favorable and follow-up angiograms showed the disappearance of the beading pattern. P.P.A. is widely used over the counter in diet pills and stimulants. Cerebral vascular complications have been rarely reported, always hemorrhagic and often associated with cerebral vasculitis. They are unrelated to duration or dosage of treatment. The mechanism is unclear but could result from several factors: chronic or paroxystic high blood pressure, immuno-allergic vasculitis, arterial spasm, direct "toxic" effect of the P.P.A. on the arterial wall may be increased by other drugs and caffeine.
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PMID:[Benign cerebral angiopathies and phenylpropanolamine]. 304 37

The purpose of this study was to determine if caffeine augments the slow-pressor response to chronic low-dose infusions of angiotensin II (AII) or the rapid-pressor response to acute infusions of AII. AII was infused (125 ng/min i.p.) for 12 d via mini-osmotic pumps in four groups of rats: group I, intact rats not treated with caffeine (n = 9); group II, intact rats treated with caffeine (0.1% in drinking water, n = 9); group III, rats previously sympathectomized with 6-hydroxydopamine, but not treated with caffeine (n = 10); and group IV, rats previously sympathectomized with 6-hydroxydopamine and treated with caffeine (n = 10). Chronic low-dose AII infusions slowly elevated systolic blood pressure in all groups. Caffeine greatly augmented this slow-pressor response to AII in intact animals; however, caffeine failed to enhance AII-induced hypertension in sympathectomized rats. Caffeine pretreatment did not enhance the rapid-pressor response to acute intravenous infusions of AII. We conclude that caffeine augmented the slow-pressor effect of chronic low-dose infusions of AII via a mechanism that involved the sympathetic nervous system.
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PMID:Caffeine enhances the slow-pressor response to angiotensin II in rats. Evidence for a caffeine-angiotensin II interaction with the sympathetic nervous system. 311 Feb 9

San Francisco bus drivers have an increased prevalence of hypertension. This study examined relationships between blood lead concentration and blood pressure in 342 drivers. The analysis reported in this study was limited to subjects not on treatment for hypertension (n = 288). Systolic and diastolic pressures varied from 102 to 173 mm Hg and from 61 to 105 mm Hg, respectively. The blood lead concentration varied from 2 to 15 micrograms/dL. The relationship between blood pressure and the logarithm of blood lead concentration was examined using multiple regression analysis. Covariates included age, body mass index, sex, race, and caffeine intake. The largest regression coefficient relating systolic blood pressure and blood lead concentration was 1.8 mm Hg/ln (micrograms/dL) [90% C. I., -1.6, 5.3]. The coefficient for diastolic blood pressure was 2.5 mm Hg/ln (micrograms/dL) [90% C. I., 0.1, 4.9]. These findings suggest effects of lead exposure at lower blood lead concentrations than those concentrations that have previously been linked with increases in blood pressure.
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PMID:Blood pressure and blood lead concentration in bus drivers. 320 32

Caffeine can produce a mild hypertensive effect for a few hours after use. Some epidemiological data relate chronic coffee intake to an increased risk of cardiovascular disease. We explored the possibility that a regular intake of caffeine-containing beverages (tea, coffee, cola) might produce a chronic increase in blood pressure and increase the likelihood of developing sustained hypertension. A random population survey of 2436 adults was made, with standardized blood pressure readings and a food-frequency questionnaire to determine the regular intake of various nutrients. We found evidence that caffeine intake was positively related to an increased diastolic blood pressure but the effect was small (less than 1 mmHg at usual caffeine intake). There was no evidence that a regular caffeine intake increases the risk of being classified as hypertensive.
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PMID:Caffeine-containing beverages and the prevalence of hypertension. 324 Dec 68


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