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Biomedical subjects

K H Rahn

Publications and source records attributed to K H Rahn.

At least 145 records · Page 8Linked to original sources
PubMed1989

Electron-probe X-ray microanalysis of sodium ion content in vascular smooth muscle cells from spontaneously hypertensive and normotensive rats.

In aortic smooth muscle cells from 12 spontaneously hypertensive rats (SHR) of the Münster strain and 11 normotensive Wistar-Kyoto rats (WKY), the intracellular Na+ content was measured by electron-probe microanalysis. Measurements were performed in aortic cryosections 3 microns thick; the Na+ content was 12.5 +/- 2.4 g/kg dry weight in SHR versus 6.96 +/- 1.1 g/kg dry weight in WKY (P less than 0.01). Thus, aortic smooth muscle cells from SHR are characterized by a markedly elevated intracellular Na+ content compared with normotensive cells. This may either be due to genetically determined disturbances in transmembrane Na+ transport or to a circulating factor affecting Na+ transport. Cellular Na+ handling may be disturbed in SHR aortic smooth muscle as it is in hypertensive blood cells.

Animals↗
PubMed1989

Verapamil and nebivolol improve carotid artery distensibility in hypertensive patients.

The effects of verapamil (a calcium antagonist) and nebivolol (a novel, selective beta 1-adrenoceptor blocker) on carotid artery distensibility and cross-sectional compliance were studied non-invasively in hypertensive patients with the use of a high-resolution multigate pulsed Doppler system. Arm blood pressure measurements were made with an automated device (Dinamap). After a 4-week washout period, 19 patients (aged 21-73 years) with essential hypertension entered a double-blind randomized placebo-controlled crossover study with 120 mg verapamil or placebo three times a day for 4 weeks. After the administration of verapamil, carotid artery distensibility and cross-sectional compliance were significantly larger (P less than 0.05) than after placebo. Using the same protocol, 29 patients (aged 25-70 years) were given 5 mg nebivolol or placebo once a day for 4 weeks. After the administration of nebivolol, carotid artery distensibility and cross-sectional compliance were significantly larger (P less than 0.05) than after placebo. In both studies no significant differences in diameter and pulse pressure were found between placebo and verapamil or nebivolol. Blood pressure was decreased similarly with both verapamil and nebivolol. These results indicate that both verapamil and nebivolol favourably influence carotid artery distensibility and cross-sectional compliance of the common carotid artery, resulting in a better management of the systolic pressure pulse. The improved carotid artery distensibility may help to protect the patient against atherosclerotic complications of hypertension.

Adrenergic beta-Antagonists↗
PubMed1989

Similar plasma atrial natriuretic factor levels in children and young adults with a high and low probability of developing hypertension: the Dutch Hypertension and Offspring Study.

The role of atrial natriuretic factor (ANF) in the genesis of primary hypertension is not clear. However, a natriuretic and blood pressure lowering effect has been observed after infusion of ANF. Therefore, subjects at risk of future hypertension might be deficient in ANF or less responsive to it. To address this question we studied ANF, sodium excretion and blood pressure in 180 young normotensive people with different probabilities of developing hypertension later in life. The 180 subjects had either two, one or no hypertensive parents. Sixty-nine offspring had a high, 58 an intermediate and 53 a small probability of developing hypertension ('high', 'mixed' and 'low' groups). Mean plasma levels of ANF did not differ among the three groups of offspring. A negative association was found between ANF and diastolic blood pressure, being most pronounced in the low-risk group. The similar levels of plasma ANF in these groups suggest that ANF is not directly related to the development of high blood pressure.

Adolescent↗
PubMed1989

Twenty-four-hour blood pressure is not dependent on endogenous circadian rhythm.

The effects of shifted working and sleeping phases on the diurnal blood pressure rhythm were investigated in 15 physically working industrial shift workers at a slowly rotated three-shift system. Ambulatory 24-h blood pressure monitoring was performed during the morning and night shifts. In the two shifts the mean 24-h blood pressure was identical. There were no differences in the blood pressure levels in the sleeping phases or in the working periods between the two 24-h cycles. Diurnal blood pressure fluctuations had equal amplitudes. Corresponding to the lag between the working period there was a phase difference of 8 h between the 24-h blood pressure curves. At this lag, there was a high correlation between the mean hourly blood pressure values (r = 0.683). Twenty-four-hour blood pressure curves during the first and last day of a night shift were nearly equal. Thus the effects of shift rotation on the 24-h blood pressure profile were fully expressed within the first 24 hours. The immediate and complete adaptation of the 24-h blood pressure curve to shifted activity and sleeping phases indicates that activity determines the diurnal blood pressure profile. The blood pressure is largely independent of internal circadian rhythm.

Adaptation, Physiological↗
PubMed1989

Can secondary hypertension be identified by twenty-four-hour ambulatory pressure monitoring?

Circadian blood pressure rhythms were examined in subjects exhibiting various forms of secondary and essential hypertension and in normotensive subjects with and without renal disease. Indirect ambulatory blood pressure recordings were performed in 284 subjects for 24 h. In contrast to patients with essential hypertension and to normotensive healthy subjects, the circadian fluctuations of blood pressure were reduced in secondary hypertensives and in normotensive renal patients. In renal hypertensives, these alterations in the diurnal blood pressure variations were dependent on the degree of renal failure. Calculations based on comparisons of the mean sleeping and mean daytime blood pressures identified 89.8% of the essential hypertensives and 72.5% of the patients with secondary hypertension. A large proportion of the patients with secondary hypertension had very high blood pressure levels during sleep, in many cases even exceeding the daytime levels. Thus, 24-h ambulatory blood pressure curves from patients with secondary and essential hypertension can be distinguished from each other. In secondary hypertension, blood pressure monitoring during both day and night is particularly useful for evaluating frequently severe nocturnal hypertension, which may require particular treatment.

Blood Pressure Determination↗
PubMed1988

[Have angiotensin-converting enzyme inhibitors improved therapy of hypertension?].

Angiotensin converting enzyme (ACE)-inhibitors combined with diuretics and, if necessary, with calcium antagonists can be used with good success for the treatment of otherwise resistant hypertension. Calcium antagonists are an alternative for physically active hypertensive patients who complain of muscular fatigue during treatment with beta-receptor-blocking agents. The calcium antagonist nifedipine has made the treatment of hypertensive emergencies much easier than with the use of clonidine and particularly sodium nitroprusside. In order to determine the place of ACE-inhibitors and of calcium antagonists in the treatment of hypertension- particularly in comparison with beta-blockers and diuretics- controlled long-term studies on the prognosis of patients with mild to moderate hypertension and on the incidence of side effects would be required.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1988

Carotid artery wall properties in normotensive and borderline hypertensive subjects of various ages.

The vessel wall properties of the common carotid artery were studied noninvasively in normotensive and borderline hypertensive male volunteers of various ages with the use of a multi-gate pulsed Doppler system. In the younger age group (20-35 y) both distensibility and cross-sectional compliance were significantly less in the borderline hypertensive group. In the older borderline hypertensive subjects (50-69 y) distensibility (p less than 0.05) and cross-sectional compliance (p = 0.06) were also less than in the control subjects. The reduced distensibility and cross-sectional compliance likely result from a decrease in arterial wall elasticity because the relative increase in common carotid artery diameter during systole is diminished in borderline hypertensives, despite the fact that their pulse pressure is similar to or higher than that in control subjects. The less pronounced differences in vessel wall properties between borderline hypertensive and normotensive volunteers in the older age group may be a consequence of the changes in these properties with age, partly masking the alterations due to borderline hypertension. Since the stiffer behavior of the common carotid artery in borderline hypertensives is associated with relatively slight changes in blood pressure, the question can be raised whether the alterations in arterial wall properties are really a result of the elevated arterial blood pressure; these alterations might develop independent of the blood pressure elevation.

Adult↗
PubMed1988

[Effects of angiotensin-converting enzyme inhibitors in hypertension].

Angiotensin-converting-enzyme(ACE)-inhibitors reduce the formation of angiotensin II from angiotensin I. These drugs cause a substantial fall in blood pressure in patients with various forms of hypertension. In particular, the combination of ACE-inhibitors with diuretics and, if necessary, additionally beta-blockers or calcium antagonists, has also been shown to be effective in patients with otherwise resistant hypertension. ACE-inhibitors may cause serious side-effects, but, on the other hand, these drugs often have a favourable effect on the quality of life during long-term treatment.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1987

The influence of antituberculosis drugs on the plasma level of verapamil.

The influence of antituberculosis drugs on the plasma level of verapamil was studied after its oral and intravenous administration. Six patients who had been treated for at least 6 months with a combination of rifampicin, ethambutol and isoniazid received a single oral dose of 40 mg verapamil. As compared to untreated subjects, the antituberculosis drugs greatly reduced the bioavailability of the calcium antagonist. Studies in patients in whom treatment with ethambutol and isoniazid had been discontinued revealed that the effect was due to rifampicin. The drugs for tuberculosis had no influence on the plasma level of verapamil when it was given intravenously. The findings can be explained by the induction of verapamil metabolizing liver enzymes in patients treated with rifampicin.

Administration, Oral↗
PubMed1987

The effects of verapamil and propranolol on exercise tolerance in hypertensive patients.

In a single-blind, placebo-controlled crossover study the effects of verapamil (450 +/- 30 mg/day) and propranolol (160 +/- 20 mg/day) on endurance time during submaximal exercise were compared in eight patients with essential hypertension. The drugs were given in randomized order. Each active drug period was preceded by a placebo phase. Endurance tests were performed during both placebo periods and treatment with verapamil and propranolol by bicycle ergometry. Both drugs were equally effective in decreasing resting blood pressure. Verapamil and propranolol reduced exercise heart rate, the effect of propranolol being more pronounced. With placebo, endurance time during exercise was 57 +/- 11 minutes; with propranolol it was 32 +/- 7 minutes (P less than 0.05). Verapamil had no influence on endurance time. The study demonstrates that in contrast to propranolol, verapamil has no influence on exercise tolerance during submaximal work in patients with hypertension.

Adult↗
PubMed1987

Metabolic effects of verapamil and propranolol during submaximal endurance exercise in patients with essential hypertension.

In contrast to beta-adrenoceptor blocking agents, calcium channel blockers do not appear to affect exercise tolerance in hypertensive subjects. A possible explanation is a difference in the metabolic effects of both types of drugs. Therefore, the effects of 4-week treatment periods with verapamil and propranolol on metabolic parameters during an endurance bicycle ergometer test were studied in eight patients with mild to moderate essential hypertension. Patients exercised at a work load which increased the heart rate to 150 bts/min during placebo. A single-blind, placebo-controlled, randomized cross-over design was used. The dose of propranolol and verapamil was adjusted to lower standing diastolic blood pressure less than 90 mmHg. Average daily doses were 155 +/- 21 mg propranolol and 390 +/- 44 mg verapamil. Exercise heart rate was reduced during propranolol and verapamil (P less than 0.01), but the reduction was more pronounced during propranolol than during verapamil (P less than 0.05). Minute ventilation and oxygen consumption were unchanged during propranolol and verapamil. The respiratory exchange ratio tended to increase during propranolol. Plasma glucose and lactate concentrations were unchanged during propranolol and verapamil. In contrast, plasma glycerol and nonesterified fatty acids were reduced during propranolol (P less than 0.05), but unchanged during verapamil. Plasma potassium levels were increased during propranolol (P less than 0.05). Despite the important direct and indirect role of calcium ions in the regulation of many metabolic processes, no effect of verapamil on metabolic parameters during submaximal exercise was found. In contrast, propranolol had an effect on fat and potassium metabolism during exercise.

Adult↗
PubMed1987

Long-term antihypertensive therapy with beta-blockers: submaximal exercise capacity and metabolic effects during exercise.

The effects of long-term (6 months) antihypertensive treatment with three different types of beta-blockers (propranolol, nonselective without ISA; pindolol, nonselective with ISA; metoprolol, beta 1-selective without ISA) on submaximal exercise capacity and metabolic variables during submaximal endurance exercise were studied in seven subjects with essential hypertension. Exercise tests were performed on a bicycle ergometer at 70% of estimated VO2 max. Similar reductions of resting and exercise blood pressure and exercise heart rate were obtained with the three beta-blockers. Exercise time was significantly reduced by all three beta-blockers during chronic antihypertensive therapy. The reduction tended to be more pronounced after 5-6 months of treatment than after 1 week (P = 0.06). During exercise, the plasma glycerol and nonesterified fatty acid concentrations were reduced. Plasma glucose concentration was reduced at the end of the exercise test during propranolol treatment only. Plasma lactate concentrations tended to be increased, but the difference was significant during pindolol treatment only. Oxygen uptake tended to decrease and respiratory exchange ratio to increase. Plasma potassium concentrations during exercise were significantly increased with all three beta-blockers. The effects on the metabolic variables during exercise were similar after 1 week and during long-term (20/24 weeks) beta-blocker treatment. The study shows that submaximal endurance exercise capacity is impaired in patients with essential hypertension on beta-blocker therapy and that the impairment is maintained during long-term antihypertensive beta-blocker treatment.

Adrenergic beta-Antagonists↗
PubMed1987

A long-term study of plasma catecholamine levels and plasma renin activity in borderline hypertension.

Blood pressure and plasma catecholamine levels were followed up for a total of 7 years in 26 subjects with borderline hypertension and in 24 normotensive subjects. During the observation period, five subjects from the borderline hypertensive group became definitely hypertensive, 10 remained in the borderline hypertensive range and in 10, blood pressure fell below borderline hypertensive levels. Of the original 24 normotensive subjects, 15 remained in the normotensive range. In seven, blood pressure rose, but did not reach borderline hypertensive levels. Three subjects were lost to follow-up. In contrast with the subjects who remained normotensive and borderline hypertensive, those who became definitely hypertensive had consistently high plasma noradrenaline concentrations at rest. Plasma adrenaline levels and plasma noradrenaline concentrations during exercise did not differ, however. The study suggests that borderline hypertensive subjects who develop definite hypertension within a few years have consistently enhanced sympathetic activity.

Adult↗
PubMed1987

The use of calcium antagonists in patients with renal failure.

Calcium antagonists are now frequently used for the treatment of high blood pressure, angina pectoris and cardiac arrhythmias. Increasingly, these drugs are also given to patients with renal failure, since several studies have demonstrated that calcium antagonists lower blood pressure in patients with renal hypertension and renal insufficiency. Relevant pharmacokinetic parameters for verapamil, nitrendipine and diltiazem are not altered in renal failure. The situation is more complex in the case of nifedipine. However, studies with repeated administration have demonstrated that the calcium antagonists verapamil, diltiazem, nifedipine and nitrendipine can be given in the same doses to patients with renal failure as to patients with normal renal function.

Calcium Channel Blockers↗
PubMed1987

Antihypertensive compounds with combined actions.

In the treatment of hypertension, drugs with different mechanisms of action are frequently combined. The rationale for this procedure is that lowering blood pressure via one mechanism often leads to the activating of processes that tend to increase blood pressure. Thus, during antihypertensive treatment with vasodilating agents, reflex stimulation of the heart occurs with increase of cardiac output. By this, the blood pressure lowering effect of the vasodilator is antagonized. Combination of several drugs may complicate therapy because of differences in the onset and the duration of action. Sometimes, there are pharmacokinetic drug interactions. By combining several blood pressure lowering mechanisms in one drug molecule, one tries to prevent these difficulties. There are now several drugs with a dual mode of action available for the treatment of hypertension. Labetalol combines alpha- and beta-receptor blocking activities. Meanwhile, there is ample experience with the use of this drug in the treatment of hypertensive patients. Labetalol can be used for acute decrease of blood pressure in hypertensive emergencies. Most often, the drug is given for chronic treatment of hypertension. The overall incidence of side effects from labetalol compares favorably with that from other drugs. In addition to side effects caused by beta-blockade, the use of labetalol may result in postural hypotension due to the alpha-receptor blocking activity. Carvedilol is a new compound that combines beta-receptor blockade and vasodilation in one molecule. The drug can be used to acutely and chronically reduce blood pressure. Carvedilol is now undergoing clinical investigation. The same is true for celiprolol, a beta 1-receptor blocking agent with alpha 2-receptor blocking activity.

Adrenergic beta-Antagonists↗