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Biomedical subjects

O Kuchel

Publications and source records attributed to O Kuchel.

At least 181 records · Page 10Linked to original sources
PubMed1975

Urinary homovanillic acid, dopamine and norepinephrine excretion in patients with essential hypertension.

Urinary excretion of dopamine, norepinephrine and homovanillic acid was measured in normotensive subjects and in patients with either labile of stable hypertension under conditions controlled for posture, sodium and potassium intake and time of day. Mean homovanillic acid excretion was 313.5 plus or minus 77.7 (SE) mug/4h in the normotensive patients. Mean values for the patients with labile or stable hypertension were significantly greater, at 2506 plus or minus 476 mug/4 h (P smaller than 0.001) and 795 plus or minus 170 mug/4 h (P smaller than 0.01), respectively. Urinary excretion of dopamine and norepinephrine tended to be elevated in patients with labile hypertension when compared with values in the control subjects and the patients with stable hypertension. The data are compatible with the hypothesis of adrenergic hyperactivity in labile hypertension and underline the biochemical heterogeneity of essential hypertension. Because the overlapping of values between control subjects and patients with labile hypertension was minimal, it is proposed that an elevated valve for urinary homovanillic acid could be used as a biochemical marker to identify the patients with labile hypertension.

Adolescent↗
PubMed1975

Sex differences in the urinary catecholamines.

Urinary excretion of dopamine, norepinephrine and epinephrine was measured in a group of adult men and women of comparable age during recumbency and then during stimulation by upright posture. Urinary norepinephrine was found to be significantly higher in women (30.3 +/- 4.4 ng/min/m2 B.S.) than in men (18.3 +/- 2.7 ng/min/m2 B.S.) during recumbency; there was no significant sex difference in dopamine and epinephrine excretion. There was no apparent trend indicating a difference in urinary catecholamine excretion during the follicular or luteal phase of the menstrual cycle. In response to upright posture, there was a significant decrease in the urinary dopamine-norepinephrine ratio in both sexes; the magnitude of the decrease was, however, significantly higher in men (-9.9 +/- 3.0) than in women (-2.05 +/- 0.72). The mechanisms of the sex differences in urinary catecholamine excretion are unknown. Clinical studies involving catecholamines have to take these sex differences into account.

Catecholamines↗
PubMed1975

Splanchnic blood flow in essential hypertension and in hypertensive patients with renal artery stenosis.

Splanchnic blood flow (SBF) was measured simultaneously with cardiac output (dye dilution) and intrarterial blood pressure by constant infusion of indocyanine green in 11 control subjects, 13 patients with essential hypertension (EH) and seven hypertensive patients with renal artery stenosis (RAS). The cardiac index (CI) was lower (P less than 0.05) in patients with EH (3.17 plus or minus 0.07 L/min/m-2) (mean plus or minus SEM) than in control subjects (3.43 plus or minus 0.09). Associated with the lower CI was a significantly (P less than 0.01) lower SBF (0.797 plus or minus 0.02 L/min/m-2 vs 0.889 plus or minus 0.04). Patients with RAS presented with higher (P less than 0.01 vs EH, nonsignificant vs control subjects) cardiac index (3.66 plus or minus 0.17) and even lower SBF (0.749 PLUS OR MINUS 0.02). Furthermore, there was a negative correlation (r = - 0.652) between the mean arterial pressure and the SBF when results for all patients were considered. The correlation remained (r = - 0.568) in the EH group and the slope of regression line was not different from that for all subjects. The CI and SBF were weakly correlated (r = 0.423) in control subjects and patients with EH, whereas in patients with RAS, a negative correlation was found (r = - 0.778). This study indicates that the SBF, although significantly decreased in patients with EH, remains proportional to the CI in control subjects and in essential hypertensive patients. No redistribution of CI in regard to the splanchnic circulation occurs in EH. In contrast, in patients with RAS a dissociation of CI and SBF occurs and the fraction of the CI which passes through the splanchnic vascular bed is markedly reduced. The close correlation between mean arterial pressure and SBF suggests that both parameters are influenced by a common pathophysiological factor.

Abdomen↗
PubMed1975

Labile (borderline) hypertension--new aspects of a common disorder.

Labile hypertension in patients under 50 years of age (the non-atherosclerotic form) was found to be characterized by higher urinary excretion of catecholamines and particularly of homovanillic acid; when further analyzed it was shown to be a heterogeneous entity with two types of patients clinically and biochemically distinguishable from each other, from control subjects and from patients with stable hypertension. Reactivity to assuming an upright posture distinguishes one type of labile hypertension having a normal postural pulse rate response from another having an excessive postural increase in pulse rate. The first group also showed normal responses of plasma norepinephrine concentration and of urinary cyclic AMP to posture. The group with excessive pulse rate response, in contrast, showed a decrease in plasma norepinephrine and an excessive increase of urinary cyclic AMP excretion in response to upright posture. The results suggest that not only circulating catecholamines but also the reactivity of their target tissues (as probably reflected by cyclic AMP measurements) are important in bringing about signs of adrenergic excess. The hypothesis that cyclic AMP changes reflect beta-adrenergic receptor reactivity is strongly favoured by data indicating qualitative differences in cyclic AMP responses to beta-adrenergic stimulation or inhibition between control subjects and those labile hypertensive patients with clinical signs of excessive sympathetic reactivity. The study stresses the need for more precise definition of labile hypertension, for dynamic clinical and biochemical correlative studies, and for consideration not only of the circulating hormones but also of the "second messengers" (such as cyclic AMP and cyclic GMP) which reflect the cellular action of hormones. Blood pressure is a very labile parameter in health and disease. In one sense, therefore, hypertension can be considered "labile" in every hypertensive patient. Usually, however, labile (or borderline) hypertension is regarded as characterized by a blood pressure over 140/90 mmHg, falling below these values with physical and emotional rest. This clinical entity, which affects some 20% (variously estimated between 16 and 30%) of the adult population, gives rise to uncertainties in both definition and prognosis. In some patients labile hypertension represents the precursor of a fixed hypertensive state, whereas in many others it remains labile throughout life, never progressing to the stable phase nor becoming associated with hypertensive cardiovascular disease.(ABSTRACT TRUNCATED AT 400 WORDS)

Catecholamines↗
PubMed1975

Urinary and plasma cyclic adenosine 3',5'-monophosphate in patients with idiopathic edema.

Urinary excretion and plasma concentrations of adenosine 3',5'-monophosphate were determined in idiopathic edema patients both at rest and after assumption of the upright position. Patients and normal subjects responded similarly to upright posture with decreases in urinary volume and creatine excretion and their urinary excretion of cyclic AMP was not significantly different. The plasma concentration of cyclic AMP was high in patients, both in the recumbent and upright positions, and its renal clearance (unlike that of creatinine) was low. Plasma cyclic AMP increased in response to upright posture both in patients and normal subjects. Even if the significance of elevated plasma cyclic AMP is unknown, its presence without an increase in urinary cyclic AMP suggests that the renal handling of cyclic AMP is abnormal is idiopathic edema; this may be related to an excessive beta-adrenergic tone.

Adult↗
PubMed1975

Effect of propranolol on plasma renin activity, renal cortex renin, and adrenal and brain isorenins in rats.

Propranolol administration to rats was studied for its effects on plasma renin activity, renal renin content, and adrenal and brain isorenins. Propranolol was given intraperitoneally at 6 and 30 mg/kg/day for a 15-day period. Pulse rate was significantly decreased. There were no effects on the isorenin content of adrenal or brain tissue or on renal renin content. Rats responded in two completely different ways with respect to plasma renin activity. Two-fifths had a total suppression of plasma renin activity; the rest had concentrations similar to those in controls. These observations are consistent with those seen during chronic administration of propranolol to hypertensive patients and suggest that its antihypertensive effect may in some patients be through the suppression of renin release. Its mechanism of action in most patients remains at present unclear.

Adrenal Glands↗
PubMed1974

Plasma adenosine 3',5'-cyclic monophosphate in human hypertension.

In a previous study we observed an increase in urinary cyclic AMP in labile hypertension in the upright position and during isoproterenol infusion, in contrast to a decrease in control subjects. In the present study we measured the plasma level of cyclic AMP in control subjects and patients with various types of hypertension. We obtained the following results: (1) plasma cyclic AMP increases in response to upright posture in control subjects and hypertensive patients; (2) values of cyclic AMP in the recumbent and upright positions are comparable in control subjects and patients with essential hypertension, but are significantly higher in those with true renovascular hypertension due to bilateral renal artery stenosis; (3) propranolol inhibits the increase of plasma cyclic AMP in response to posture in control subjects, but has an opposite effect in labile hypertension where there is a further increase; (4) the rise in blood pressure in pheochromocytoma is associated with a considerable increase in plasma cyclic AMP.Present and previous data suggest that kidney handling of cyclic AMP is abnormal in hypertension, and that the specific defect may be related to the type of hypertension.

Adolescent↗
PubMed1974

Screening programs for hypertension.

MAJOR SCREENING PROGRAMS FOR HYPERTENSION ARE NECESSARY FOR THE FOLLOWING REASONS: (a) the 12 to 15% prevalence of hypertension in the North American population; (b) the high proportion of hypertensive patients who are inadequately treated or whose disease is not even recognized; (c) the fact that in too many medical centres hypertension is poorly investigated or considered an insignificant finding; (d) the demonstration by many groups, especially the Framingham study, of hypertension as the major factor in the occurrence of severe cardiovascular disease; and (e) the achievement of a marked decrease in severe cardiovascular complications following adequate treatment. But such screening programs are of little value if unaccompanied by a major educational effort directed not only to the public but also to the medical profession, and a parallel increase in the funding of biomedical research into the basic physiopathological mechanisms of hypertension.

Adolescent↗
PubMed1973

Effect of propranolol on cyclic AMP excretion and plasma renin activity in labile essentrial hypertension.

Labile hypertension is often associated with elevated cardiac output, increased plasma renin activity (PRA) and urinary cyclic AMP excretion in response to upright posture and to isoproterenol. The beta-blocking agent propranolol was demonstrated to be an effective therapeutic agent in this condition. The effect of posture on cyclic AMP, PRA, pulse rate and blood pressure was therefore studied during the administration of propranolol and a placebo in patients with labile hypertension. With the patient on placebo, upright posture induced an increase in pulse rate, cyclic AMP excretion and PRA. Propranolol administration decreased the recumbent and upright blood pressures, pulse rate and PRA. Cyclic AMP excretion remained unchanged in the recumbent position but the postural increase was abolished. No appreciable changes in catecholamine excretion occurred during propranolol administration. Propranolol normalizes some humoral as well as hemodynamic abnormalities of labile hypertension and therefore may be of benefit in long-term treatment and possibly also in the prevention of stable hypertension.

Adolescent↗
PubMed1973

Renin in hypertension: how important as a risk factor?

An analysis of the plasma renin levels in relation to the incidence of severe cardiovascular complications (coronary thrombosis, stroke, ruptured aortic aneurysm) was made in 325 patients with various types of hypertension. These patients had one to four measurements of plasma renin activity taken under standard conditions of sodium intake and posture in the period 1963-68. The follow-up was 5 to 10 years in the four groups of hypertensive patients (essential hypertension, malignant hypertension, hypertension secondary to renal parenchymatous disease and hypertension caused by, or associated with, renal artery obstruction). For all 325 patients, the incidence of such complications was 23.6, 20.4 and 44.7% in the low, normal and high renin groups. These findings are at variance with the claim that renin constitutes a serious risk factor in hypertensive patients, especially if it is isolated from other parameters such as the level of diastolic pressure, the adequacy of kidney function, the effectiveness of dietary and drug management of hypertension, and especially the presence or absence of atherosclerotic lesions of the large vessels at the time of the renin determination.

Adult↗