[Treatment of hypertension in the elderly]

The effect of treating hypertension in the elderly (aged 60-65 years and above), and isolated systolic hypertension in particular, has not been adequately documented. In three recent studies, however, a good effect in respect of cardiovascular end points has been observed in this group of patients. We have previously suggested pharmacological treatment of a diastolic blood pressure above 100mm Hg after three to six months' observation and non-pharmacological intervention. In a patient with essential hypertension, and with no concomitant disease, systolic blood pressure should also be taken into account, and when this exceeds (100 + age) mm Hg after the same period of observation the patient should be treated pharmacologically. If a patient shows additional indications for treatment of high blood pressure, the level for initiating treatment may be lower. As of today, diuretics and beta-blockers have proven effective in reducing cardiovascular morbidity and mortality, while data on the other antihypertensive agents are still lacking.

Does blood pressure reduction necessarily compromise cardiac function or renal hemodynamics? Effects of the angiotensin-converting enzyme inhibitor quinapril

Clinical studies indicate that the angiotensin-converting enzyme inhibitor quinapril is an effective antihypertensive agent when administered once daily. At the end of a 4-week, double-blind crossover trial comparing quinapril and placebo, patients were admitted for a hemodynamic profile study 12 hours after taking the previous dose. A final 20 mg dose of quinapril had no additional effect on blood pressure. This is interesting inasmuch as the plasma half-life of the active metabolite quinaprilat is approximately 2 hours and the effective accumulation half-life is approximately 3 hours. The blood pressure reduction in patients with mild hypertension receiving long-term quinapril therapy may be more closely related to prolonged angiotensin-converting enzyme inhibition or to an effect on tissue angiotensin II concentration than to the plasma half-life. This may be the case particularly for cardiac output and renal circulation, because quinapril lowers total vascular resistance without increasing cardiac output or disturbing autoregulation of renal blood flow. Reduced ventricular wall stress, improved diastolic function, and lower renal perfusion pressure may spare cardiac function and glomeruli from hypertensive vascular damage.

[Treatment of hypertension in Norway. Indications, therapeutic intensity and economic aspects]

The Norwegian Society of Hypertension held its third scientific meeting in February 1991. One of the issues discussed was when to initiate drug treatment of uncomplicated essential hypertension and what level of blood pressure should be the goal of treatment. The American guidelines suggest that a blood pressure of 140/90 mm Hg or higher should be treated pharmacologically, whereas WHO suggests 160/95 mm Hg. The consensus at the meeting was that, in otherwise healthy subjects without end organ damage, a diastolic blood pressure of 100 mm Hg or more over three to six months should be treated with drugs, and that a safe goal would be around 135-140/85-90 mm Hg.

Haemodynamic and neurohumoral effects of cold pressor test in severe heart failure

The effect of a cold pressor test (CPT) on haemodynamics in relation to general and regional sympathetic activity and arginin vasopressin (AVP), was studied in eleven patients with severe congestive heart failure (CHF). Compared to an age-matched control group (C), resting arterial plasma noradrenaline (NA) (419 +/- 77 vs. 182 +/- 15 pg ml-1), and adrenaline (A) (142 +/- 28 vs 54 +/- 10 pg ml-1) were higher (P less than 0.05) in CHF. AVP showed no significant difference (14 +/- 4 vs. 9 +/- 4 pg ml-1). During CPT systolic and diastolic blood pressure and systemic vascular resistance increased (P less than 0.01), as did NA (delta 114 +/- 39 pg ml-1, P less than 0.01), A (delta 33 +/- 10 pg ml-1, P less than 0.01) and heart rate (delta 10 beats min-1, P less than 0.01). The myocardial v-a difference of NA decreased (P less than 0.05), but was unchanged across the renal vascular bed during CPT. The a-v difference of NA in the hepatic vascular bed, and fractional extraction of A in the coronary sinus, renal and hepatic vascular beds remained unchanged during CPT. AVP did not change significantly and no change in cardiac index or left ventricular filling pressure was observed during CPT. These data suggest that despite an increased activation of the sympathetic nervous system at rest, a further increase in blood pressure and catecholamines took place during CPT. Thus, the effect of a CPT which activates the central sympathetic system seems not to be altered in patients with severe CHF.

[Ambulatory non-invasive 24-hour blood pressure measurement--do we need it?]

The introduction of non-invasive, portable, automatic blood pressure measurement devices enables characterization of the blood pressure profile throughout the day in an ambulatory setting. The article advises against uncritical use. 24-hour ambulatory blood pressure measurements have become a valuable tool in scientific research, however, especially in studies dealing with antihypertensive efficacy. In hypertensive patients with "white coat hypertension", important data cannot be obtained without the use of 24-hour ambulatory blood pressure monitoring or blood pressure measurement at home.

The epinephrine-blood platelet connection with special reference to essential hypertension

About three decades ago it was shown by an aggregometer that epinephrine activated blood platelets, and it was proposed that platelets could be the link between stress and cardiovascular disease. During the past 10 years this hypothesis has been tested in clinical studies. It has been found that subjects with hypertension consistently have raised plasma catecholamine levels and in particular elevated epinephrine levels. Arterial but not venous epinephrine concentrations correlated with plasma concentrations of the platelet-release reaction marker beta-thromboglobulin (BTG). Plasma BTG is elevated in hypertensive patients, and psychological stress (i.e., hypertension labeling) stimulates plasma epinephrine and BTG. When a physiologic dose of epinephrine is infused into essential hypertensive patients, platelet counts, platelet size, and plasma BTG concentrations increase more than in normotensive subjects. Data suggest that there is a connection between psychological stress, plasma epinephrine levels, and platelet function, especially in patients with essential hypertension.

Faster and more reliable absorption of adrenaline by aerosol inhalation than by subcutaneous injection

1. The aim of the present study was to compare absorption of adrenaline given by aerosol spray inhalation with absorption after subcutaneous injection. 2. Arterial plasma adrenaline was measured in nine healthy volunteers following adrenaline administration by both methods. 3. Following inhalation of 20 puffs of adrenaline aerosol, 0.15 mg/puff, a peak arterial adrenaline concentration after 1 min and a rapid fall to baseline from this peak occurred. 4. When given by subcutaneous injection absorption was slower with a peak arterial adrenaline concentration after 4 min. The fall in arterial adrenaline from this peak level was not statistically significant within 30 min after injection. 5. There was less intersubject variation of arterial adrenaline concentration following inhalation when compared with injection. 6. Heart rate, blood pressure and finger tremor followed the changes in arterial adrenaline concentrations. 7. These results indicate that absorption is more reliable when adrenaline is given by inhalation. The rapid fall in arterial adrenaline following inhalation, suggests that repeated inhalations are necessary when such adrenaline therapy is required.

Hyperkinetic borderline hypertension in Tecumseh, Michigan

Of 691 healthy (untreated) villagers of Tecumseh, Michigan (average age 32.6 years), 99 had a clinical blood pressure exceeding 140/90 mmHg. Thirty-seven per cent of these borderline hypertensives had increased heart rate, cardiac index, forearm blood flow and plasma norepinephrine. These subjects had elevated self-determined home blood pressure (average of 14 measurements). The present hyperkinetic borderlines had elevated blood pressure at 5, 8, 21 and 23 years of age and their parents also had higher blood pressure. The prevalence of high blood pressure in Tecumseh, its long history, elevated blood pressure readings outside the physician's office and family background of hypertension, suggests that the hyperkinetic state is a significant clinical condition. Previous studies on hospital-based populations proved that the hyperkinetic state is caused by an excessive autonomic drive. The association of the hyperkinetic state with elevated norepinephrine in this study suggests that a sympathetic hyperactivity is present in a large proportion of unselected subjects with mild blood pressure elevation.

Platelet function during antihypertensive treatment with quinapril, a novel angiotensin converting enzyme inhibitor

The effect of various antihypertensive medications on platelet function is of increasing interest. Conflicting effects of captopril on platelet function are reported and the impact of angiotensin converting enzyme (ACE) inhibitors not containing a sulfhydryl group such as enalapril, lisinopril, and quinapril on platelet function remains unstudied. Therefore, the aim of the present study was to examine the effect of antihypertensive treatment with quinapril, a novel ACE inhibitor not containing a sulfhydryl group, on platelet function. Ten white men (age range of 32-61 years) with untreated mild-to-moderate essential hypertension (supine diastolic blood pressure greater than 95 mm Hg) were treated with 4 weeks each of placebo and quinapril in a double-blind, randomized, crossover design. Quinapril (20 mg twice a day) significantly lowered systolic (p less than 0.01) and diastolic blood pressure (p less than 0.01) without any significant effect on heart rate or plasma catecholamines. No significant change was noted for in vitro platelet aggregation induced by epinephrine, ADP, or collagen. Plasma concentrations of the platelet release factors beta-thromboglobulin and platelet factor 4 did not change, nor did the platelet content of norepinephrine, platelet weight (mg/10 ml of blood), circulating platelet count, or platelet size. Thus, as assessed by a broad spectrum of platelet parameters, we found that antihypertensive treatment with quinapril has no significant effect on platelet function in patients with mild-to-moderate essential hypertension. These "platelet-neutral" properties of quinapril suggest that quinapril, both from a thromboembolic and a hemostatic point of view, may be a rather safe agent for treatment of hypertension.

Awareness of hypertension increases blood pressure and sympathetic responses to cold pressor test

The present study was aimed at examining the effects of awareness of hypertension on blood pressure and sympathetic responses to the cold pressor test. Nineteen-year-old men with similarly elevated mean blood pressure at a medical screening, but without knowledge of this, were randomized into two groups. The first group (n = 16) was sent a letter saying that their pressure was too high, and the second (n = 13) was sent a neutral letter. Information increased mean blood pressure both after 15 min sitting, by an average of 11.5 mm Hg (P less than .01), and after 30 min supine rest, by an average of 4.5 mm Hg (P less than .05). Changes in heart rate (8.4 +/- 2.4 v 1.9 +/- 1.7 beats/min) and plasma epinephrine (0.11 +/- 0.04 v 0.01 +/- 0.03 nmol/L) during execution of a cold pressor test were significantly greater in the informed group (P less than .05). Plasma dopamine was lower in the informed group (P less than .05). Thus, psychological stress caused by the awareness of hypertension may increase blood pressure and sympathetic responses to a provocative maneuver. Ideally, studies on sympathetic function in essential hypertension should be undertaken on subjects unaware of their blood pressure status.

"White coat" versus "sustained" borderline hypertension in Tecumseh, Michigan

During a survey of young subjects not receiving treatment for hypertension in Tecumseh, Michigan, clinic and self-monitored blood pressures taken at home (14 readings in 7 days) were obtained in 737 subjects (387 men, 350 women, average age 31.5 years). Hypertension in the clinic was diagnosed if the clinic blood pressure exceeded 140 mm Hg systolic or 90 mm Hg diastolic. In the absence of firm criteria for what constitutes hypertension at home, subjects whose average home blood pressure was in the upper decile of the whole population were considered to have hypertension at home. By these criteria, 7.1% of the whole population had "white coat" hypertension (i.e., high clinic but not elevated home readings). The prevalence of "sustained" hypertension (i.e., high readings in the clinic and at home) was 5.1%. Subjects with white coat and sustained borderline hypertension in Tecumseh were very similar. Both groups showed, at previous examinations (at ages 5, 8, 21, and 23 years), significantly higher blood pressure readings than the normotensive subjects. As young adults (average age 33.3 years), the parents of both hypertensive groups had significantly higher blood pressure readings than the parents of normotensive subjects. Both hypertensive groups had faster heart rates, higher systemic vascular resistance, and higher minimal forearm vascular resistance. Both hypertensive groups were more overweight, had higher plasma triglycerides, insulin, and insulin/glucose ratios than normotensive subjects. The white coat hypertensive group also had lower values of high density lipoprotein than the normotensive group. White coat hypertension is a frequent condition.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal haemodynamic and sympathetic responses to head-up tilt in essential hypertension

Nine mild-to-moderate hypertensive patients (HT), aged 41 +/- 0.6 years (mean +/- SEM) and nine age-matched normotensive control subjects (NT) were tilted to 60 degrees for 10 min. During tilt, both systolic (S) blood pressure (BP) (p less than 0.01) and diastolic (D) BP (p less than 0.05) increased in HT, but not in NT. At supine rest renal blood flow was higher in HT than in NT and increased by 17% in HT during tilt, while a decrease of 13% was observed in NT (p less than 0.05). Renal vascular resistance was unchanged in HT during tilt, while a significant increase (p less than 0.01) was observed in NT. Arterial plasma noradrenaline increased in both groups (p less than 0.05) during tilt, significantly more in HT than in NT (p less than 0.05). No statistically significant difference was observed between the groups in renal catecholamine uptake or release. Our data indicate enhanced general sympathetic and circulatory responses to tilt in subjects with mild-to-moderate essential hypertension. However, the enhanced haemodynamic and sympathetic responses were not shared by hypertensive kidneys and renovascular resistance remained unaffected by tilt.

Increased arterial adrenaline is related to pain in uncomplicated myocardial infarction

Plasma levels of catecholamines, beta-thromboglobulin (BTG) and arginine vasopressin (AVP), and degree of pain were examined in 22 patients with suspected uncomplicated myocardial infarction within 24 h following onset of chest pain. Sixteen patients developed infarction with peak creatine phosphokinase at 1280 Ul-1 (range 293-3770 Ul-1). Fifteen healthy men served as controls (C). Arterial adrenaline levels were significantly higher in patients with pain (1.15 +/- 0.23 nmol l-1, n = 8, mean value +/- SEM) than in those without pain (0.60 +/- 0.10 nmol l-1, n = 14, P less than 0.05). Plasma catecholamines were moderately but significantly elevated in myocardial infarction; the concentration of arterial adrenaline was 0.83 +/- 0.14 nmol l-1 and that of arterial noradrenaline was 2.70 +/- 0.28 nmol l-1 compared with 0.44 +/- 0.04 nmol l-1 (P less than 0.025) and 1.47 +/- 0.05 nmol l-1 (P less than 0.0005), respectively, in C. One week later, plasma catecholamines had returned to baseline levels. Plasma BTG showed borderline elevation (1.0 +/- 0.1 pmol l-1) compared with C (0.6 +/- 0.1 pmol l-1, P = 0.04), and remained unchanged 1 week later. Plasma AVP was at baseline level. Uncomplicated myocardial infarction, regardless of size, was associated with only moderately increased sympathetic tone. Plasma adrenaline was related more to the degree of pain than to the presence of acute myocardial infarction. Arterial adrenaline may be a sensitive marker of sympatho-adrenal activity related to pain.

Correlations between psychological and physiological responses to acute flight phobia stress

Exposure of phobic subjects to real-life psychological stress may induce a high level of anxiety and be better than laboratory experiments for studies of physiological responses to psychological stress in human research. Therefore, by introducing natural psychological stress, i.e. actual flying in subjects with flight phobia (n = 23), the present study aimed at testing the hypothesis that there is, during mental stress, a direct relationship between the level of anxiety and the responses in the physiological variables blood pressure, heart rate and plasma catecholamines. Plasma adrenaline, heart rate, blood pressure and perceived anxiety measured by three different scales increased highly significantly during flight whereas plasma noradrenaline did not change. No direct relationship was found between the physiological and psychological variables. Thus, the physiological responses to natural psychological stress in terms of phobic anxiety may be definite, but the way the responses are related is less clear.

Hemodynamic effects of quinapril, a novel angiotensin-converting enzyme inhibitor

The hemodynamic effects of quinapril, a novel nonsulfhydryl-containing angiotensin-converting enzyme (ACE) inhibitor, were assessed in 10 patients with mild-to-moderate essential hypertension. Compared with placebo, quinapril (20 mg) administered twice daily for 4 weeks significantly lowered blood pressure by decreasing total peripheral resistance without producing tachycardia, an increase in cardiac output, or a rise in plasma catecholamines. Quinapril significantly reduced renal, but not forearm, vascular resistance. Renal blood flow, glomerular filtration rate, and filtration fraction remained unchanged. Left ventricular wall stress was markedly reduced by quinapril, but during the relatively short treatment period, only a nonsignificant trend toward reduction in left ventricular mass was observed. These findings suggest that quinapril is an effective antihypertensive agent that lowers peripheral resistance without increasing cardiac output or disturbing autoregulation of renal hemodynamics.

Increased erythrocyte magnesium in never treated essential hypertension

In the present study we aimed at evaluating the intracellular concentrations of magnesium, potassium and sodium in 50-year-old, otherwise healthy white men with never treated, essential hypertension (n = 12) and in normotensive control subjects (n = 12) matched for age, sex, race, height, weight and smoking habits. Intraerythrocyte magnesium was significantly increased in the hypertensive group (P less than .001) and correlated positively and significantly to blood pressure in the total group (P less than .01). The intracellular potassium to sodium ratio tended to be lower in the hypertensive group (P less than .05). Thus, the present study supports increased intracellular magnesium probably unrelated to intracellular potassium-sodium imbalance in never treated, essential hypertension.

Awareness of high blood pressure stimulates platelet release reaction

The present study aimed at testing the hypothesis of a link between mental stress and blood platelet function. Twenty-nine 19-year-old men were recruited from the 98th percentile of mean blood pressure (116 mmHg) at a routine medical screening. They were not informed about their elevated blood pressures at the time of the screening. One year later they were randomized into two groups. Group 1 (n = 16) was exposed to mental stress by a letter informing them about their high blood pressure, while group 2 (n = 13) was sent a neutral letter. At an examination 2 weeks later, heart rate (p less than 0.05) and plasma adrenaline (p less than 0.05) responses to a cold pressor test were exaggerated in the informed group. The plasma beta-thromboglobulin (beta TG) concentration was elevated in the informed group (p less than 0.05) as was mean blood pressure (p less than 0.05). beta TG correlated positively with hematocrit (r = 0.59, p less than 0.005) and mean blood pressure (r = 0.43, p less than 0.05), and negatively with plasma HDL (r = -0.61, p = 0.001). The study shows that awareness of hypertension induces a hyperadrenergic state which is associated with the platelet release reaction. Under these circumstances platelet release seems to be correlated to established coronary heart disease risk factors.

Increased erythrocyte magnesium content in essential hypertension

The present study aimed at testing the hypothesis of decreased erythrocyte magnesium content and magnesium deficiency in essential hypertension. Atomic absorption was used to measure the erythrocyte content of total magnesium in 50-year-old otherwise healthy white males with essential hypertension (n = 12, blood pressure (mean +/- SE) 155 +/- 4/109 +/- 2 mmHg) that had never been treated and in normotensive control subjects (n = 12, blood pressure 128 +/- 2/88 +/- 1 mmHg) matched for age, sex, race, height, weight and smoking habits. The erythrocyte magnesium content was significantly increased in the hypertensive group (2.266 +/- 0.063 vs 1.903 +/- 0.069 mmol/l erythrocytes, p less than 0.001). No significant difference between the groups was detected for serum concentration or the 24-h urinary excretion of magnesium. In conclusion, the present study indicates increased rather than decreased erythrocyte content of magnesium in 50-year-old white males with 'never-treated', essential hypertension. Magnesium deficiency is, therefore, unlikely in this subset of critically selected and matched hypertensive patients.

Effects of beta 1- and beta 2-blockade on blood pressure and sympathetic responses to flight phobia stress

Cardiovascular and sympathoadrenal effects of short-term oral treatment with beta 1-blockade (atenolol, 50 mg, administered two times) and beta 2-blockade (ICI 118,551, 50 mg, administered three times) were compared with placebo during actual flying in subjects with flight phobia (n = 34). beta 1-Blockade lowered resting blood pressure and heart rate and prevented a heart rate response but not a blood pressure response to this psychologic stress. beta 2-Blockade minimally lowered resting heart rate and prevented a heart rate response, but it failed to lower resting blood pressure or blood pressure response to the stress. Plasma epinephrine increased with all three treatments and more with beta 1-blockade than with placebo. Plasma norepinephrine decreased with administration of beta 2-blockade. Thus neither beta 1- nor beta 2-blockade prevents an increase in blood pressure during acute flight phobia stress. Increased plasma epinephrine seems to be the sympathetic variable that is closest related to this increase in blood pressure. Norepinephrine may be less consistently related to the blood pressure rise during flight phobia stress as shown by the decrease in plasma norepinephrine with administration of beta 2-blockade.

Effects of selective beta-adrenoceptor blockade on anxiety associated with flight phobia

The present study is aimed at studying the effects of selective beta-adrenoceptor blockade on anxiety in subjects with flight phobia. Using an incomplete block design subjects received a beta-1 (atenolol 2 x 50 mg), a beta-2 (ICI 118 551 3 x 50 mg) selective blocking drug, or placebo on three occasions over a 16 h period under double-blind conditions prior to a 1/2 h flight. The same procedure was repeated 4 weeks later. Thirty-four subjects completed this double-blind, two-period crossover study. Self-reporting by the Alderley Park State Anxiety Questionnaire, Global Flight Anxiety and Treatment Preference showed a moderate but significant effect of atenolol in alleviating especially somatic symptoms of flight anxiety in addition to an overall effect in the treatment of this entity (p<0.01). ICI 118 551 was ineffective in alleviating any of the important symptoms of flight phobia. These results may imply that the effect of beta-adrenoceptor blockade in reducing phobic anxiety may be more a result of beta-1 than of beta-2 blockade. Beta-1 adrenoceptor blockade may be an alternative treatment of flight phobia, particularly when the symptoms are of somatic character and when intellectual performance is expected shortly after the flight.

Childhood traumas and psychosocial characteristics of 50-year-old men with essential hypertension

The aim of the present study was to describe childhood traumas and other psychosocial characteristics of middle-aged men with never-treated essential hypertension. Hypertensive (N = 17) and normotensive (N = 18) 50-yr-old men were selected from the Oslo Study of Cardiovascular Diseases based on their age, sex, blood pressure and otherwise healthy condition without chronic medication. They were interviewed semistructurally by a psychiatrist who was unaware of their blood pressure status. Eleven hypertensives and five normotensives (p less than 0.05) had experienced considerable traumas in childhood, e.g. death of a parent, psychotic parent, separation from one or both parents, or beating by an alcoholic father. The hypertensives had fewer siblings and fewer sons than the normotensives (p less than 0.05). The normotensives were better educated; 12 had finished at least 12 yr in school as opposed to one hypertensive (p less than 0.01). The normotensives' parents (p less than 0.05) and spouses (p less than 0.001) were better educated than the hypertensives'. The normotensives' yearly income was higher (p less than 0.05). The hypertensives showed more Type A behaviour patterns (p less than 0.05) and lower Spielberger State Curiosity (p less than 0.05). Although the groups were small, they were rigorously characterized. These results therefore suggest that middle-aged men with essential hypertension have more childhood traumas and lower educational and income levels and that these social characteristics are associated with Type A behaviour patterns. The study favours a psychosocial understanding of the pathogenesis of essential hypertension.

Increased erythrocyte magnesium in untreated essential hypertension

In the present study we tested the hypothesis of magnesium deficiency and intracellular magnesium depletion in essential hypertension. Atomic absorption was used to determine the erythrocyte content of magnesium in 50-year-old otherwise healthy white men with never-treated, essential hypertension (n = 12, supine blood pressure 155 +/- 4/109 +/- 2 mmHg) and in a group of particularly well-matched normotensive control subjects. The erythrocyte magnesium content was higher in the hypertensive group (P less than 0.001). No significant difference between the groups was detected for serum concentration or the 24-h urinary excretion of the magnesium. In conclusion, magnesium deficiency is unlikely in white middle-aged hypertensive men.

Arterial plasma norepinephrine correlates to blood pressure in middle-aged men with sustained essential hypertension

Increased plasma catecholamine levels assessed from the venous blood have been found in a number of studies of younger patients with essential hypertension, but hypertensive-normotensive differences could not easily be demonstrated in subjects above 40 years of age. For several reasons, measurement of arterial plasma catecholamines may be a more sensitive tool for the detection of hypertensive-normotensive differences. The present study therefore aimed at examining both venous and arterial plasma catecholamines in a group of white men, all 50 years of age, with never-treated, established essential hypertension (n = 61, blood pressure 165 +/- 2/112 +/- 1 mm Hg, means +/- SE) and comparing them with a similar group of normotensive men (n = 51, blood pressure 128 +/- 1/85 +/- 1 mm Hg). Arterial and venous plasma epinephrine, heart rate, and body weight were significantly elevated in the hypertensive group. Plasma norepinephrine was similar between the groups in the venous blood, whereas in the arterial blood the values in hypertensive subjects were moderately, but significantly increased (p less than 0.03). However, stepwise multiple regression analysis suggested arterial plasma norepinephrine was the only significant independent explanatory variable of raised blood pressure in the hypertensive group (r = 0.51, t = 4.05, p = 0.0002). Such a relationship was not found in the normotensive group. Thus based on measurements in arterial blood, we conclude that plasma norepinephrine, representing sympathetic tone, may be an important pathogenetic factor for high blood pressure in middle-aged men with established hypertension.

Effect of dopamine and dopamine-antagonist infusion on blood platelet count, size and release reaction in hypertensive and normotensive subjects

To examine the effect of dopamine on in vivo platelet function and a possible platelet contribution to the clearance of dopamine we measured platelet count, platelet size and plasma concentration of the platelet specific protein beta-thromboglobulin (BTG) in groups of 40 year old untreated hypertensive and normotensive men. One hypertensive (n = 10) and one normotensive (n = 10) group received dopamine infusion at doses from 0.5 to 2.0 micrograms/kg/min which increased plasma dopamine 100-fold from baseline. Two other groups of hypertensive (n = 10) and normotensive (n = 11) subjects received 10 mg of the dopamine antagonist metoclopramide intravenously, upon which serum prolactin concentration increased 10-fold. No significant effect on platelet function in any group was observed during these interventions. Platelet phenol-sulphotransferase may contribute to dopamine conjugation. However, the selected platelet parameters correlated only weakly with dopamine kinetics during the infusion. Neither dopamine nor a dopamine antagonist altered the selected platelet parameters, nor did these parameters influence the clearance of dopamine during a short-lasting pharmacological infusion.

Plasma catecholamines in some airline passengers

Assuming that the act of flying may provoke mental stress and increments in plasma catecholamines, in-flight plasma catecholamines were compared in two groups of passengers: a group of ordinary passengers (Group 1, n = 15) and a group of passengers who had just completed a cognitive, behavioural treatment programme against flight phobia (Group 2, n = 13). No difference in catecholamines was observed between the groups. However, 10 of the subjects in Group 1 and 12 of the subjects in Group 2 had in-flight plasma adrenaline higher than the highest mean +2 SD (above 0.40 nmol/l) of resting plasma adrenaline observed in healthy subjects in a long series of studies previously or simultaneously done in our laboratory. Subjects in Group 2 (n = 12) showed an average decrease of 50% from in-flight to post-flight plasma adrenaline. Plasma noradrenaline values were not elevated compared to normal resting levels, but an average reduction of 24% was observed between in-flight and post-flight in Group 2. We could not detect any difference between passengers treated for flight phobia and ordinary passengers. However, in-flight plasma catecholamines, particularly adrenaline, seem to be elevated in some airline passengers of various backgrounds. The most plausible explanation seems to be the discomfort and fear some people feel when flying; however, we cannot exclude that the physiological act of flying per se increased plasma catecholamines. Relatively larger variations in plasma adrenaline compared to noradrenaline may favour the first of these two possible explanations.

Effect of beta-adrenergic blockade on hormonal responses during continuous and intermittent exercise

The modifying effect on exercise performance and neuroendocrine response of the nonselective beta blocker timolol (10 mg b.i.d. for 5 days) and the beta 1-selective beta blocker metoprolol (100 mg b.i.d. for 5 days) was studied. The hormones studied were growth hormone, prolactin, cortisol, renin, epinephrine, dopamine, and norepinephrine. The response was studied during short-term maximal dynamic exercise, using two different exercise protocols; continuous (n = 11) and intermittent (n = 9) bicycle ergometry, in normal healthy young men. Accumulated work on placebo was nearly identical in the two studies, but was significantly reduced by 10.4% and 6.6% with timolol and by 4.7% and 6.7% with metoprolol, during continuous and intermittent exercise, respectively. During continuous exercise, accumulated work was 5.8% lower (p less than 0.05) with timolol than with metoprolol. The hormonal plasma concentrations of all hormones except renin were higher during continuous exercise than during intermittent exercise. Beta blockade had no effect on baseline hormonal levels, but the response was markedly changed during exercise. Maximum epinephrine, cortisol, and prolactin responses increased after beta blockade; dopamine remained nearly unchanged; while the renin responses were attenuated. Norepinephrine concentrations were slightly increased during continuous exercise by beta blockade and rose in direct proportion to the increase in workload. During intermittent exercise, maximum norepinephrine levels were significantly reduced by beta blockade compared with placebo. Thus the effect of beta 1-selective and nonselective beta receptor blockade on circulating hormones does not seem to explain the reduced exercise capacity following beta blockade.

Hyper-responsiveness to low-dose epinephrine infusion in mild essential hypertension

The present study was undertaken to evaluate the effects of intravenous infusion of small amounts of epinephrine on haemodynamics, renal electrolyte excretion and blood platelets in essential hypertension. Arterial plasma epinephrine concentrations were increased during the infusion to approximately 2.5 nmol/l both in a group of 40-year-old men with untreated mild essential hypertension (blood pressure 154 +/- 3/100 +/- 3 mmHg, n = 12) and in a group of age-matched male controls (124 +/- 3/78 +/- 2 mmHg, n = 11). In the hypertensive group only, mean blood pressure decreased, forearm blood flow increased, forearm vascular resistance decreased (P less than 0.001 for all) and the urinary excretion of sodium and potassium increased (P less than 0.01 for both). The hypertensive group also responded with an increase in plasma beta-thromboglobulin (P less than 0.05), blood platelet size (P less than 0.05) and a higher increase in platelet counts than in the normotensive group (P less than 0.05). Thus, in several ways the hypertensive patients showed a hyper-responsiveness to amounts of epinephrine which corresponds well to the plasma concentration achieved during psychological and physical activity.

Decreased platelet-free dopamine and unchanged noradrenaline and adrenaline in essential hypertension

The content of free-catecholamines in blood platelets is much higher than in plasma and platelet catecholamines must be taken up from plasma, since platelets lack the enzymes for catecholamine synthesis. There is some evidence that platelet catecholamine content under certain circumstances may be an integrated measure of plasma catecholamine concentrations over time. Platelet-free catecholamines were therefore assayed in 18 untreated patients with essential hypertension and in 16 normotensive control subjects. Mean platelet-free dopamine in the hypertensive group was 3.7 +/- 0.4 pg/mg platelet weight, i.e. significantly less than the 6.5 +/- 0.9 pg/mg found in the normotensive (p less than 0.005). Platelet contents of noradrenaline and adrenaline did not differ. Decreased platelet-free dopamine and unchanged platelet noradrenaline and adrenaline persisted after adjustment for increased body weight in the hypertensive group. Although the reasons for decreased platelet-free dopamine in the hypertensive group remain unknown, this finding may add to previous result showing facilitated release of granular contents from blood platelets in patients with essential hypertension. Our data do not support platelet levels of free-catecholamines to be a marker of increased sympathetic tone in essential hypertension.

Decreased serum phosphate in essential hypertension. Related to increased sympathetic tone

Forty-year old men with untreated mild essential hypertension (n = 35) had decreased serum phosphate (P less than 0.001) concomitant with elevated resting plasma epinephrine (P less than 0.05) and heart rate (P less than 0.001) compared with age-matched, normotensive control men (n = 44). Blood pressure correlated negatively with serum phosphate (P less than 0.001) and positively with plasma epinephrine (P less than 0.01) and heart rate (P less than 0.01). Serum phosphate was significantly lowered during infusion of epinephrine, increasing arterial plasma epinephrine within the lower pathophysiological range corresponding to arousal reactions. Serum concentrations of immunoreactive parathyroid hormone were unchanged. Thus, hypophosphatemia in patients with mild essential hypertension appears to be inversely related to sympathetic adrenal tone and may be caused by increased plasma epinephrine within pathophysiologic arterial concentrations.

Sodium depletion increases platelet and plasma catecholamines in hypertensive men

The catecholamine content in blood platelets is considerably higher than that in plasma, and platelet catecholamines must be taken up from plasma, since blood platelets lack enzymes for catecholamine synthesis. However, it is unknown whether platelets take up and store catecholamines during physiological in vivo increments in plasma catecholamines. Previously untreated 50-year-old men (n = 17) with mild to moderate essential hypertension were given a low sodium diet for 2 weeks. Urinary excretion of sodium decreased from 201 +/- 11 (SE) to 24 +/- 5 and 19 +/- 4 mmol/24 hr after 1 and 2 weeks, respectively. During the first week, the blood platelet concentration of norepinephrine increased from 27.2 +/- 2.9 to 39.6 +/- 4.7 pg/mg (p less than 0.005) and venous plasma norepinephrine increased from 3.7 +/- 0.4 to 5.6 +/- 0.5 pg/ml (p less than 0.005), and venous plasma dopamine increased from 26 +/- 4 to 41 +/- 5 pg/ml (p less than 0.05). During the second week, both plasma and platelet norepinephrine and dopamine remained elevated. Platelet epinephrine showed a small increase from baseline to the second week (p less than 0.05), but no concomitant increase in plasma epinephrine occurred. Thus, sodium depletion increases both platelet and plasma catecholamines and blood platelets may take up catecholamines in vivo. Platelet catecholamine content may be an integrated measure of plasma catecholamine concentrations during variations caused by sodium depletion.

The effects of naloxone and timolol on plasma catecholamine levels during short-term dynamic exercise

In order to study the role of opioid- and betareceptors on exercise-induced catecholamine responses, the effects of acute intravenous administration of 1 and 4 mg naloxone and of the non-selective betablocker timolol 2 mg of on circulating concentrations of adrenalin, noradrenaline and dopamine during exercise to exhaustion were examined in eight normal, healthy young men, using a double-blind, randomized, placebo-controlled design. During maximal exercise, adrenalin levels increased from 71 +/- 17 to 821 +/- 235 pg/ml (p less than 0.05), noradrenaline from 355 +/- 58 to 4235 +/- 1031 pg/ml (p less than 0.05), and dopamine from 72 +/- 20 to 178 +/- 44 pg/ml (p less than 0.05). Naloxone did not influence basal or exercise-induced noradrenaline responses. Timolol clearly augmented peak adrenalin concentration at maximal exercise capacity (1543 +/- 510 pg/ml, p less than 0.05). Basal noradrenaline level was increased (546 +/- 86 pg/ml, p less than 0.05), while exercise-induced noradrenaline level was reduced (2954 +/- 594 pg/ml, p less than 0.05) in proportion to the reduction in maximal exercise capacity during timolol treatment. Neither naloxone nor timolol affected dopamine levels. No additive effect was seen with the combination of naloxone and timolol. It is concluded that the opioid peptides are probably not involved in noradrenaline and dopamine responses, whereas betablockers change the catecholamine response to short-term maximal exercise.

Myocardial potassium uptake and catecholamine release during cardiac sympathetic nerve stimulation

To determine whether sympathetic nerve stimulation induces a significant potassium uptake in the myocardium, the changes in myocardial potassium balance, catecholamine release, lactate uptake, and oxygen consumption were recorded in eight anaesthetised open chest pigs during electrical stimulation of the right intermediate cardiac nerve at 10 Hz. Potassium concentrations were continuously measured by polyvinylchloride valinomycin minielectrodes in arterial and coronary sinus blood. Potassium concentration in coronary sinus blood fell to a nadir 0.42(0.21-0.61) mmol.litre-1 below control values (median and 95% confidence interval) and resulted in a peak potassium uptake of 65(38-102) mumol.min-1 100 g-1 after 2.5(2.0-3.0) min, which correlated (r = 0.94, p less than 0.001) with cardiac noradrenaline release. Accumulated myocardial potassium uptake amounted to 139(82-241) mumol.100 g-1 when a stable potassium concentration difference between arterial and coronary sinus blood was reached after 5.5(4.25-6.50) min. Cardiac contractility (LV dP/dt), myocardial oxygen consumption, and lactate uptake rose from control to peak potassium uptake (p less than 0.001) by 140%, 158%, and 92% respectively. Coronary sinus blood noradrenaline and adrenaline concentrations rose significantly (p less than 0.01) from 58(44-87) pg.ml-1 at control to 2208(1159-5627) pg.ml-1 at peak uptake and from 15(11-19) pg.ml-1 to 85(64-230) pg.ml-1 respectively. Arterial noradrenaline increased from 29(19-41) pg.ml-1 to 374(176-640) pg.ml-1 and arterial adrenaline rose from 15(11-23) pg.ml-1 to 31(24-52) pg.ml-1 (p less than 0.001). It is concluded that sympathetic nerve stimulation induces a substantial myocardial potassium uptake in a dose dependent relation to cardiac noradrenaline release and alters the contractile and metabolic state of the heart substantially with only minor changes in arterial catecholamine concentration.

Does increased platelet release normalize during anti-hypertensive treatment?

Blood platelet function was evaluated in 10 men, all 50 years old, with untreated, mild hypertension. Each patient was examined four times: At the beginning of the study, after 5 weeks on placebo treatment, after the following 5 weeks on propranolol 160 mg daily, and finally after a second period of 5 weeks on placebo. At baseline the plasma level of the platelet release product beta-thromboglobulin (BTG) was 41.6 (30.5-57.0) micrograms/l (median and 95% confidence interval). During the first placebo period BTG was normalized to 21.0 (14.1-25.9) micrograms/l. While systolic blood pressure and heart rate fell during beta-adrenergic receptor blockade, BTG remained unchanged throughout the rest of the observation periods. Platelet size increased significantly during treatment with beta-blocker. The present study indicates that the normalization of elevated platelet function which previously has been reported to occur during anti-hypertensive drug therapy, may be explained by patient adaptation to the blood sampling procedure.

Increased platelet size and release reaction in essential hypertension

Basal platelet function was measured in 35 40-year-old men with untreated mild essential hypertension and compared with 44 age-matched normotensive men. The groups differed significantly with respect to platelet size in venous blood (hypertensive, 7.46 +/- 0.10 X 10(-15) l versus normotensive, 7.11 +/- 0.09 X 10(-15) l; P = 0.01) and arterial concentration of the platelet-specific protein beta-thromboglobulin (hypertensive, 1.11 +/- 0.23 nmol/l versus normotensive, 0.59 +/- 0.04 nmol/l; P = 0.02). The normotensive subjects had significantly higher beta-thromboglobulin (BTG) in venous than in arterial blood (P less than 0.01). The hypertensive men showed no such difference. In contrast to the normotensive subjects, the hypertensive group had reduced arterial compared with venous platelet count (P less than 0.01). This may reflect an increased liability in the hypertensive subjects to lose platelets through adherence to the cannula during arterial blood sampling. The above findings point to increased platelet activity in essential hypertension, particularly in arterial blood.

Endocrine and haemodynamic responses to graded dopamine infusion in essential hypertension

Hormonal, mean arterial blood pressure, forearm blood flow and heart rate responses to graded dopamine infusion (0.5-2.0 micrograms/kg/min) were examined in 10 men with untreated essential hypertension WHO group I (147 +/- 4/100 +/- 1 mmHg, means +/- SE), and in 10 normotensive men (129 +/- 2/85 +/- 1 mmHg), all 40 years old. Another 12 normotensive men (126 +/- 3/80 +/- 2 mmHg) were given only saline infusion. Dopamine increased heart rate significantly in the hypertensive group (8 +/- 2 beats/min, p less than 0.001), but the heart rate remained unchanged in the normotensive group (1 +/- 1 beats/min, NS). Although dopamine infusion tended to decrease mean blood pressure, the changes were not significantly different from those observed in the control group. No change in forearm blood flow was observed in either group. In the groups given dopamine, prolactin levels decreased only slightly compared to the control group given saline, the decrement tending to be more pronounced in the hypertensive group. Plasma vasopressin remained unchanged in both groups during dopamine infusion. These results indicate that hypertensive patients exhibit increased sensitivity to the cardiovascular effects of dopamine.

Severe sodium restriction alone and with potassium supplementation does not alter blood lipoproteins in essential hypertension

Seventeen 50-year-old men, previously untreated and all with mild to moderate essential hypertension, were given a low sodium diet for 2 weeks. During the second week, the diet was supplemented with potassium. Urinary excretion of Na+ decreased from 201 +/- 11 to 24 +/- 5 and 19 +/- 4 mmol 24 h-1, respectively, after 1 and 2 weeks (means +/- SE) while the urinary Na+: K+ ratio changed from 2:1 to 1:4 and 1:11. Despite significant changes in blood pressure, body weight, serum electrolytes, sympathetic noradrenergic tone, haemoglobin concentration and haematocrit, no significant change appeared in serum total cholesterol, HDL-cholesterol or triglycerides. Thus, low sodium diet alone and combined with potassium supplementation seems neutral to blood lipoproteins in the treatment of essential hypertension.

Decreased central dopaminergic activity in essential hypertension

Baseline serum prolactin (PRL) was found to be similar in 35 men with untreated essential hypertension (149 +/- 2/98 +/- 1 mmHg; means +/- s.e.) and 44 healthy normotensive men (126 +/- 1/80 +/- 1 mmHg), all 40 years old. A correlation between baseline PRL and aldosterone was found in the normotensive (r = 0.534, P less than 0.001), but not in the hypertensive group (r = -0.011, NS). Ten subjects from each group received intravenous metoclopramide, a competitive dopamine antagonist, while another 12 normotensive subjects were given saline only, and the effect on PRL, vasopressin (AVP) and catecholamines was followed. An exaggerated PRL response to metoclopramide was observed in the hypertensive group compared with the normotensive (P less than 0.05), and the mean normotensive peak value never exceeded the hypertensive. Plasma noradrenaline increased significantly compared with baseline (P less than 0.05) and the control group (P less than 0.001), concomitant with increased heart rate (P less than 0.05), after the administration of metoclopramide both in the hypertensive and normotensive group. After intravenous injection of metoclopramide, forearm blood flow increased significantly by 50% in the hypertensive (P less than 0.001), and 80% in the normotensive group (P less than 0.001) compared with the control group. Mean blood pressure remained unchanged as did plasma AVP, dopamine and adrenaline. The present study indicates an altered central dopaminergic activity in essential hypertension. Even at rest, endogenous dopamine exerts a modulating effect on noradrenaline release in both hypertensive and normotensive men.

Aging and urinary vasopressin excretion in healthy men

The influence of age on urinary excretion of arginine vasopressin (antidiuretic hormone) was examined in three groups of healthy men, 25 +/- 1 (n = 12), 40 (n = 44) and 50 years of age (n = 28) respectively. Despite increasing plasma vasopressin with progressive age (2.5 +/- 0.6 vs. 3.5 +/- 0.4 vs. 7.4 +/- 1.0 ng/l, respectively) (means +/- SE), urinary excretion of vasopressin turned out similar (6.7 +/- 1.0 vs. 6.8 +/- 0.8 vs. 6.9 +/- 0.6 ng/h). No differences in sodium excretion, serum osmolality and creatinine clearance appeared that could explain these findings. The present results suggest that age-related impairment of renal concentrating capacity is compensated for by increasing circulating plasma vasopressin. Furthermore, differences in tubular handling of the hormone with age may explain the present findings, and may be another compensatory mechanism for decreased urinary concentrating ability.

Increased platelet release reaction in 50-year-old men with essential hypertension: correlation with atherogenic cholesterol fractions

Beta-thromboglobulin (BTG) is a platelet-specific release product. Plasma BTG was significantly increased (p less than 0.01) in 50-year-old, untreated essential hypertensive men (1.22 +/- 0.13 nmol/L, n = 39, mean +/- SE) compared to 50-year-old, healthy normotensive control men (0.82 +/- 0.07 nmol/L, n = 31). Plasma BTG in the hypertensive group correlated significantly with the total serum cholesterol concentration (r = 0.47, p less than 0.01) and with the atherogenic cholesterol fractions low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL) cholesterol (r = 0.50, p less than 0.01). In the normotensive group, no significant correlation was observed between plasma BTG and total serum cholesterol (r = 0.14) or between plasma BTG and LDL + VLDL cholesterol (r = 0.08). Neither was any significant correlation found between plasma BTG and serum high-density lipoprotein (HDL) cholesterol or total triglycerides in either group. Thus, middle-aged men with untreated essential hypertension have an increased blood platelet release reaction related to their concentrations of atherogenic blood lipids. This relationship may be of pathogenetic importance for atherogenesis in hypertension.

Increased plasma noradrenaline during severe sodium restriction does not stimulate platelet release in essential hypertension

Seventeen 50-year old hypertensive men, previously untreated with blood pressure 157 +/- 4/110 +/- 2 mmHg (means +/- SE) were given a low sodium diet for 2 weeks. During the second week, the diet was supplemented with potassium. The urinary Na+/K+ excretion ratio changed from 2:1 to 1:4 and 1:11, respectively. Sympathetic noradrenergic tone increased considerably during the first week. Thus, venous plasma noradrenaline increased from 254 +/- 22 to 347 +/- 28 pg/ml (p less than 0.001) and arterial concentration from 253 +/- 36 to 317 +/- 42 pg/ml (n = 10, p less than 0.001). No significant change was observed in sympathetic adrenal tone as reflected by normal plasma adrenaline in venous (42 +/- 5 vs 43 +/- 6 pg/ml, ns) or arterial blood (71 +/- 10 vs 82 +/- 15 pg/ml, n = 10, ns) or in venous plasma concentration of the blood platelet release product beta-thromboglobulin (BTG) (50 +/- 8 vs 43 +/- 5 ng/ml, ns). During the second week sympathetic noradrenergic tone remained highly significantly elevated compared to baseline but still no change in plasma adrenaline or plasma BTG was found. Thus, whereas sodium depletion did increase plasma noradrenaline concentration markedly in these hypertensive men, no change in adrenaline concentration was observed, and blood platelet release reaction was unchanged. Plasma noradrenaline within the physiological concentration range does not seem to serve as a regulator of in vivo platelet function.

Plasma adrenaline and noradrenaline during orthostasis in man: the importance of arterial sampling

Plasma adrenaline and noradrenaline were measured in arterial blood and in forearm venous blood during supine rest and after 30 min standing in normotensive, healthy 50-year-old men (n = 16). After 30 min standing, venous noradrenaline had increased from 1.61 +/- 0.11 to 4.22 +/- 0.30 nmol/l and arterial from 1.43 +/- 0.06 to 2.93 +/- 0.15 nmol/l. Orthostasis induced a seven-fold increment in the forearm arterial-venous difference of noradrenaline from -0.18 +/- 0.08 to -1.29 +/- 0.25 nmol/l (p less than 0.001). Orthostasis more than doubled the forearm arterial-venous difference of adrenaline from 0.15 +/- 0.03 to 0.31 +/- 0.05 nmol/l (p less than 0.001) since arterial adrenaline increased from 0.31 +/- 0.03 to 0.53 +/- 0.05 nmol/l and venous from 0.16 +/- 0.02 to 0.22 +/- 0.02 nmol/l. Arterial adrenaline correlated significantly with venous in the supine (r = 0.64, p less than 0.01) but not in the standing position (r = 0.34, NS). The results indicate that arterial concentrations of adrenaline are a much better indicator of sympatho-adrenal activity during orthostasis than peripheral venous concentrations. For noradrenaline, measurements of arterial concentrations during the orthostatic manoeuvre seem to provide information about the total noradrenergic sympathetic reactivity, while the corresponding measurements in peripheral venous blood represent the forearm locally.

Enhanced platelet release reaction related to arterial plasma adrenaline and blood pressure in pre-eclampsia

The platelet release product beta-thromboglobulin (BTG) in venous plasma, and arterial and venous catecholamines were measured in 13 severe pre-eclamptic and 13 normotensive pregnant women. In the pre-eclamptic group, BTG was significantly higher and the platelet count significantly lower than in the normotensive pregnant group. In the pre-eclamptic group, arterial concentrations were significantly higher for adrenaline, noradrenaline and dopamine, whereas in venous plasma only adrenaline and dopamine were higher. Significant positive correlations appeared in the pre-eclamptic patients between venous BTG and arterial adrenaline (r = 0.82), arterial noradrenaline (r = 0.76) and venous adrenaline (r = 0.55). In the pre-eclamptic group, BTG also highly correlated with systolic (r = 0.84) and diastolic blood pressure (r = 0.77) and heart rate (r = 0.67). These findings indicate that sympathetic nervous tone, as measured by arterial and venous plasma catecholamines, is a good predictor of in-vivo blood platelet activation. In pre-eclampsia, increased sympathetic tone may play a key role in platelet activation and consumption and thus in the activation of the coagulation system.