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Biomedical subjects

P Coruzzi

Publications and source records attributed to P Coruzzi.

At least 37 records · Page 2Linked to original sources
PubMed1989

The antinatriuretic effect of dopaminergic blockade during volume expansion is independent of circulating atrial natriuretic factor.

1. Ten normal subjects were subjected to 2 h water immersion with and without pharmacological dopaminergic blockade with either metoclopramide (group I) or domperidone (group II). 2. In group I, urinary sodium excretion showed a marked increase during water immersion alone, whereas it was blunted during water immersion plus dopaminergic blockade with metoclopramide (P less than 0.05 vs water immersion alone, n = 5). Plasma aldosterone was significantly suppressed by water immersion alone (P less than 0.05), but remained unchanged during water immersion plus metoclopramide. Plasma atrial natriuretic factor showed similar augmentation during water immersion alone and during water immersion plus metoclopramide. 3. Another five subjects (group II) were studied during water immersion alone and during water immersion plus dopaminergic blockade with domperidone. In this group the increase in urinary sodium excretion was similarly blunted by dopaminergic blockade. Plasma atrial natriuretic factor was equally elevated during water immersion alone and during water immersion plus domperidone, but aldosterone was suppressed by both water immersion alone and water immersion plus domperidone. 4. Our findings suggest that water immersion-induced atrial natriuretic factor release is independent of dopaminergic activity. Dopamine blockade is able to blunt significantly both water immersion-induced natriuresis and plasma aldosterone suppression, independently of the marked elevation of circulating atrial natriuretic factor, via a mechanism involving type 2 dopaminergic receptors.

Adult↗
PubMed1988

Role of renal hemodynamics in the exaggerated natriuresis of essential hypertension.

Extracellular fluid volume expansion is known to produce exaggerated natriuresis in essential hypertension. In order to assess the role of hemodynamic and intrarenal physical factors upon natriuretic response to central volume expansion, two hour water immersion (WI) experiments were made in six uncomplicated essential hypertensives and six normotensive healthy controls. Before and during WI we measured mean arterial pressure (MAP), urine flow (V/min), sodium (UNaV) and potassium (UKV) excretion, glomerular filtration rate (GFR), effective renal plasma flow (ERPF) and intrarenal (wedged) venous pressure (IRVP). In comparison with normotensive controls, the exaggerated natriuretic response in hypertensives (P less than 0.05 for UNaV during WI) was associated with an enhanced vasodilating response as demonstrated by a greater increase in ERPF (P less than 0.05) and by a more pronounced fall in calculated renal precapillary resistances (P less than 0.05). A more significant increase in IRVP was found in hypertensive group (P less than 0.05). Glomerular filtration rate (GFR) did not change in either group during WI. MAP, unchanged in normotensives, was significantly reduced in hypertensives (P less than 0.05), while remaining in the hypertensive range. These findings suggest that intrarenal physical factors play a major role in determining the exaggerated natriuresis during WI in hypertensive man.

Adult↗
PubMed1988

Circulating opioid peptides during water immersion in normal man.

1. This study was designed to evaluate variations in plasma beta-endorphin, methionine-enkephalin, adrenocorticotropic hormone and serum prolactin in healthy volunteers during head-out water immersion. 2. Water immersion induced an increase in methionine-enkephalin plasma levels, which was associated with a significant fall in mean arterial pressure and heart rate. 3. Conversely, a suppression of plasma beta-endorphin, adrenocorticotropic hormone and serum prolactin was detected during water immersion. 4. We suggest that a dopaminergic inhibitory control mechanism may be involved in regulating circulating levels of beta-endorphin, adrenocorticotropic hormone and prolactin in normal subjects undergoing extracellular fluid volume expansion produced by water immersion.

Adrenocorticotropic Hormone↗
PubMed1988

Abnormal renal responses to calcium entry blockade in normotensive offspring of hypertensive parents.

In nine young normotensive subjects with no family history of hypertension and nine age-matched normotensive subjects with one parent with essential hypertension, effective renal plasma flow (p-aminohippuric acid clearance), glomerular filtration rate (inulin clearance), and excretion of sodium and exogenously administered lithium were measured for 90 minutes before and after administration of a single 20-mg oral dose of the calcium entry blocker nifedipine. Segmental tubular handling of fluid and sodium was estimated using lithium clearance as a marker of proximal tubular reabsorption. Nifedipine did not cause any change in subjects with no family history of hypertension, but in those with one hypertensive parent there was a marked increase in effective renal plasma flow (from 644 +/- 39 to 847 +/- 42 [SEM] ml/min x 1.73 m2; p less than 0.001) and a decrease in filtration fraction (from 17.6 +/- 1.0 to 12.6 +/- 0.4%; p less than 0.001), while the glomerular filtration rate was unchanged, thus suggesting a prevailing efferent vasodilation. Sodium excretion rate (p less than 0.02) and fractional sodium excretion (p less than 0.025) increased slightly but significantly in subjects with one hypertensive parent, but not in normotensive subjects with no family history of hypertension. Lithium clearance also rose (from 29.0 +/- 2.0 to 32.8 +/- 1.9 ml/min, p less than 0.001), and the derived value of fractional proximal reabsorption diminished (from 75.8 +/- 1.0 to 71.3 +/- 1.2%, p less than 0.001). Estimated distal delivery of sodium and absolute distal sodium reabsorption both increased significantly (p less than 0.005), while fractional distal sodium reabsorption was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Influence of cardiopulmonary receptors on the bradycardic responses to carotid baroreceptor stimulation in man.

Animal studies have shown that arterial baroreflexes are modulated by reflexes originating from the cardiopulmonary volume receptors, and that this modulation consists of a reduction of the inhibitory influence exerted by arterial baroreceptors on the heart and peripheral circulation. This has not been confirmed in man, however, in whom no reduction in the bradycardic response to carotid baroreceptor stimulation has been observed after the mild increase in central venous pressure (right atrial catheter) and cardiopulmonary receptor activity provided by passive leg raising. In seven normotensive subjects carotid baroreceptors were gradedly stimulated by progressively increasing carotid transmural pressure through a neck chamber device, the resulting reflex lengthening in R-R interval being measured in the two-three cardiac cycles immediately after the baroreceptor stimulus. This manoeuvre was performed in control conditions and repeated during a head-out water immersion which increased central venous pressure (right atrial catheter) from 1.5 +/- 0.2 to 12.0 +/- 0.9 mmHg (mean +/- SE), thereby providing a marked increase in the cardiopulmonary receptor stimulus. In the control condition graded stimulation of the baroreceptors caused a progressive lengthening in R-R interval, the maximal effect being + 477.4 +/- 57.2 ms. Immersion increased the R-R interval from 774.2 +/- 3.2 to 961.6 +/- 5.8 ms (P less than 0.01) and reduced mean arterial pressure (cuff measurement) from 96.0 +/- 1.0 to 82.3 +/- 0.9 mmHg. The changes in R-R interval induced by carotid baroreceptor stimulation were virtually identical with those observed in the absence of immersion.

Adult↗
PubMed1987

Dopamine blockade abolishes the exaggerated natriuresis of essential hypertension.

We studied natriuresis during central hypervolaemia by immersing eight normal subjects and eight patients with uncomplicated essential hypertension up to the neck in water, either in the absence (study 1) or presence (study 2) of dopamine blockade by metoclopramide. Water immersion without metoclopramide induced an exaggerated natriuresis in hypertensives compared with normotensives (P less than 0.001). This occurred in the presence of identical hormonal (plasma renin activity, plasma aldosterone and prolactin), renal (creatinine clearance) and pressor responses in both groups (study 1). The marked natriuresis seen during water immersion alone in normotensives was significantly blunted (P less than 0.02) but not abolished during water immersion with addition of metoclopramide. On the other hand, the exaggerated natriuresis found in hypertensives during water immersion alone was completely abolished during water immersion plus dopamine blockade by metoclopramide (study 2). Similar hormonal, renal and pressor changes were detected in both normotensive and hypertensive subjects during water immersion plus metoclopramide administration. Our data demonstrate that metoclopramide abolishes the exaggerated natriuretic response seen in hypertensives during volume expansion produced by water immersion, and suggest that dopamine may play a critical role in mediating the hypernatriuresis of essential hypertension.

Adult↗
PubMed1986

[Paraneoplastic polymyalgia rheumatica. Case contribution].

Polymyalgia rheumatica (PMR) is an inflammatory disease which mainly affects the elderly and is highly responsive to steroid therapy. PMR can be associated with giant cell arteritis as well as with malignancy. Three cases of malignant neoplasms of the digestive apparatus beginning with a clinical picture similar to that of the "idiopathic" PMR, but with poor response to steroid therapy are presented. In one case the primary neoplasm was found only at the autopsy. These observations suggest that a careful clinical evaluation and a long follow-up are necessary for a correct diagnosis of "idiopathic" PMR.

Aged↗
PubMed1986

Renal hemodynamics and natriuresis during water immersion in normal humans.

The renal vascular and functional responses to acute "central hypervolemia" by water immersion to the neck were determined in six normal subjects. During isotonic-isooncotic expansion by water immersion there was a significant increase in urine flow from 1.1 +/- 0.1 to 6.9 +/- 1.0 ml/min (p less than 0.05) and sodium excretion from 99.1 +/- 8.8 to 300 +/- 28 mu Eq/min (p less than 0.05). Glomerular filtration rate did not change while renal blood flow significantly increased during water immersion. Deep intrarenal venous pressure (IRVP) increased from 18.2 +/- 1.4 to 32 +/- 1.7 mmHg (p less than 0.05) while mean arterial pressure was unchanged. This marked natriuresis seen during water immersion was associated with reduced renal vascular resistance and increased deep intrarenal venous pressure demonstrating that continued natriuresis could relate to increased capillary hydrostatic pressure.

Adult↗
PubMed1986

Dopamine blockade and natriuresis during water immersion in normal man.

Natriuresis was studied during water immersion in eight normal subjects either in the absence or in the presence of dopamine blockade by domperidone. Creatinine clearance showed no significant changes; urine flow remained significantly above control values during water immersion, implying persistent suppression of antidiuretic hormone. The marked natriuresis seen during water immersion alone was significantly blunted (P less than 0.05) but not abolished during water immersion plus domperidone. Suppression of the renin-aldosterone system by water immersion alone was not significantly different from that obtained during water immersion plus dopamine blockade. On the contrary, plasma prolactin levels, previously suppressed during water immersion alone, were significantly stimulated during water immersion plus domperidone, thus indirectly suggesting a role of dopamine in mediating the blunted natriuresis seen during water immersion.

Adult↗
PubMed1985

Cardiovascular, baroreflex and humoral responses in hypertensive patients during nicardipine therapy.

Cardiovascular, baroreflex and humoral responses were evaluated in 8 patients with essential hypertension during a control period and then after oral treatment for 5 days with nicardipine hydrochloride 60 mg/d, a calcium channel antagonist. Systolic, diastolic and mean arterial cuff pressures fell after the treatment from 145.7, 98.6 and 114 mmHg control to 136.5, 86.1 and 102.9 mmHg. Heart rate increased from 71 to 78.7 beats/min indicating activation of the baroreflex control mechanism. Neurally mediated changes in the cardiovascular responses to an increase in carotid baroceptor activity and to dynamic exercise were not affected by the drug, nor was the renin-aldosterone system. Thus, a clinically dose of nicardipine significantly reduced mean arterial pressure, whilst preserving circulatory homeostasis.

Adult↗
PubMed1985

Renin-aldosterone system suppression during water immersion in renovascular hypertension.

We studied renin-aldosterone system behaviour in five renovascular hypertensive patients during central hypervolaemia by water immersion to the neck. Water immersion significantly suppressed the high peripheral renin levels of the patients despite an autonomic renin secretion from the stenotic kidney, a significant reduction of mean blood pressure and an increase in distal tubule sodium concentration. The effect of immersion on plasma aldosterone appeared to be primarily mediated via suppression of plasma renin activity (PRA). Our data suggest that: (a) the renin secretion is mainly modulated by cardiopulmonary receptors activity; (b) the neurogenic reflex control of plasma renin activity is very effective in renovascular hypertension.

Adult↗
PubMed1985

Low-pressure receptor activity and exaggerated natriuresis in essential hypertension.

Urinary sodium excretion, central hemodynamics, and mean arterial pressure (MAP) were studied in 7 normal subjects and 19 hypertensive patients during both central hypervolemia by water immersion to the neck (NI) and extracellular volume expansion by i.v. saline infusion. During 2-hour NI, 12 out of the 19 hypertensives exhibited a significant fall in MAP (p less than 0.001). Exaggerated natriuresis did not occur in these patients (ns). In the remaining 7 hypertensive patients in whom, during NI, MAP was unchanged, exaggerated natriuresis was found (p less than 0.001). During saline infusion, MAP was either unchanged or increased and exaggerated natriuresis was found in all hypertensive patients (p less than 0.001) previously submitted to NI. Our findings suggest that a high MAP is a major determinant of exaggerated natriuresis in arterial hypertension.

Adolescent↗
PubMed1984

Effects of 'central hypervolemia' by Water immersion on renin-aldosterone system and ACTH-cortisol axis in hemodialyzed patients.

Water immersion up to the neck (WI) results in a central hypervolemia; the increased atrial pressure, evoked by this maneuver, stimulates low pressure receptors (LPR) which exert tonic inhibition on sympathetic activity and suppresses both the renin (PRA)-aldosterone (PA) system and the ACTH-cortisol axis in normal man. In hemodialyzed patients (HP), in whom autonomic neuropathy has been frequently found, PRA and ACTH were not suppressed during WI while plasma cortisol and PA were reduced. Other modulators, like dopamine, are supposed to be involved in regulating cortisol and PA levels in HP.

Adrenocorticotropic Hormone↗
PubMed1982

[Effects of passive semiorthostatic cardiopulmonary hematic centralization (by immersion in water) on hydrosaline elimination and on the renin-angiotensin-aldosterone system in essential hypertension].

In 25 patients with essential hypertension and 9 control subjects we have studied the effects of central hypervolemia during water immersion on both renin-angiotensin-aldosterone system and renal function (diuresis volume and urine excretion of Na, k and osmoles). Reduction of blood pressure, plasma renin activity and aldosterone was found to be similar in both groups; renal excretion of water, Na, K and osmoles was significantly higher in the hypertensive group compared to the controls. These urinary features may be related to a reduced proximal tubular reabsorption by cardiorenal reflex due to cardiopulmonary volume receptors stimulation without any change of GFR measured as the creatinine clearance. The urinary pattern, observed during water immersion in hypertensive group without any change of plasma sodium, osmolality or protein concentration, was comparable to "exaggerated natriuresis"; this may suggest that also "exaggerated natriuresis" is due either to renal vasodilatation or to renal tubular sympathetic activity reduction secondary to a cardiorenal reflex by cardiopulmonary volume expansion.

Adolescent↗
PubMed1980

The influence of renal function on the elimination kinetics of sulbenicillin in man.

Serum concentration and urinary excretion following a single i.v. dose of 1 g Sulbenicillin (SB) have been studied in 13 subjects with different degrees of renal insufficiency and 4 control subjects. With normal GFR, serum half-life averages 27 min, with GFR between 45 and 14 ml/min, 1,5 hours, with GFR below 8-10 ml/min, 4,6 hours (maximum 7 hours). The usually recommended dosage schedule is 1 g every 6 hours. Only when GFR falls below 8-10 ml/min, the interval between doses must be changed; 1 g every 8-12 hours should be given under these conditions. However, in cases of severe extrarenal or urinary tract infections due to antibiotic-resistant strains of E. coli, Ps. aeruginosa, Pr. morganii, a first dose of 2-4 g SB should be given, followed by maintenance half-doses (1-2 g SB) every half-life.

Adult↗