PubMed HealthSearch

Biomedical subjects

G Norbiato

Publications and source records attributed to G Norbiato.

At least 19 recordsLinked to original sources

Angiotensin converting enzyme binding sites in human heart and lung: comparison with rat tissues.

1. Angiotensin converting enzyme (ACE), a dipeptidyl carboxypeptidase which catalyzes the final activation step in the formation of angiotensin II, was identified by radioligand studies in rat heart and lung. In this work we identified ACE binding sites in human left ventricle and lung by radioligand binding using the ACE inhibitor [3H]-ramiprilat in all tissues tested was saturable, temperature and zinc-dependent, and inhibited by EDTA. In human left ventricle homogenate we found a density of binding sites of 121 +/- 15 fmol mg-1 protein (n = 4) with an affinity (Kd) of 850 +/- 55 pM, whereas in rat left ventricle the same values were 23 +/- 4 fmol mg-1 protein and 315 +/- 30 pM, (n = 4), respectively. 3. [3H]-ramiprilat binding to rat (n = 4) and human lung (n = 4) showed a binding site density of 2132 +/- 155 and 1085 +/- 51 fmol mg-1 protein respectively with an affinity of 639 +/- 54 and 325 +/- 22 pM. The lung:heart ratio of ACE binding site density was about 9:1 in man and 100:1 in rat. 4. The binding affinities of 13 ACE inhibitors were evaluated on human heart and lung: the drugs tested showed a wide range of affinities for the ACE binding sites in both tissues, and the affinity for lung was significantly greater than for heart for most of the drugs. 5. The greater potency of some ACE inhibitors in displacing [3H]-ramiprilat in human lung compared with the heart indicates differences between ACE binding sites in these tissues and suggests the possibility of a selective organ-targeted therapeutic approach.

Adult

Altered vasopressin response to metoclopramide in multiple system atrophy: evidence of a cholinergic defect in the hypothalamus.

Multiple system atrophy (MSA) is a heterogeneous group of central neurological degenerations often associated with diffuse deterioration of the hypothalamic cholinergic neurons. In the hypothesis of an altered cholinergic regulation of vasopressin release, we evaluated vasopressin response to metoclopramide (20 mg i.v.), a cholinomimetic agonist, in 12 MSA patients. In the same patients the hemodynamic and osmolal control of vasopressin was also evaluated. We found that MSA patients had significantly lower basal plasma vasopressin values and higher plasma osmolality than control subjects. However, they displayed a normal vasopressin response to osmotic stimulation. During head-up tilting, orthostatic hypotension occurred in all patients, and the vasopressin response to hypotension was severely blunted in 5 of 12 patients, thus demonstrating the presence of a lesion of the afferent noradrenergic pathways. Metoclopramide increased vasopressin in control subjects, whereas MSA patients did not display any increase in vasopressin. These results clearly indicate that cholinergic neurons that regulate vasopressin release are damaged in MSA. Such an alteration may be dissociated from the lesion of the afferent noradrenergic pathways. As a consequence of the altered vasopressin release, MSA patients show lower plasma vasopressin levels with consequent propensity to dehydration and hypovolemia, which may further aggravate their hypotension.

Autonomic Nervous System Diseases

Cortisol resistance in acquired immunodeficiency syndrome.

This study concerns 9 iv drug abusers with acquired immunodeficiency syndrome (AIDS) who developed hypercortisolism without the clinical signs or metabolic consequences of hypercortisolism. All patients were characterized by an Addisonian picture (weakness, weight loss, hypotension, hyponatremia, and intense mucocutaneous melanosis). An acquired form of peripheral resistance to glucocorticoids was suspected. We, therefore, examined glucocorticoid receptor characteristics on mononuclear leukocytes by measuring [3H]dexamethasone binding and the effect of dexamethasone on [3H]thymidine incorporation, which is one of the effects of glucocorticoid receptor activation. Glucocorticoid receptor density was increased in AIDS patients with an Addisonian picture (group 1; 16.2 +/- 9.4 fmol/million cells) compared to values in 12 AIDS patients without an Addisonian picture (group 2; 6.05 +/- 2.6 fmol/million cells; P less than 0.01) and sex- and age-matched controls (3.15 +/- 2.3 fmol/million cells; P less than 0.01). The affinity of glucocorticoid receptors (Kd) was strikingly decreased (9.36 +/- 3.44 nM in group 1; 3.2 +/- 1.5 nM in group 2; 2.0 +/- 0.8 nM in controls; P less than 0.01). [3H]Thymidine incorporation was decreased dose-dependently by dexamethasone in controls and patients; the effect was significantly blunted (P less than 0.05) in group 1 patients, which suggests that activation of glucocorticoid receptor is impaired as a result of the glucocorticoid receptor abnormality. In conclusion, AIDS patients with hypercortisolism and clinical features of peripheral resistance to glucocorticoids are characterized by abnormal glucocorticoid receptors on lymphocytes. Resistance to glucocorticoids implies a complex change in immune-endocrine function, which may be important in the course of immunodeficiency syndrome.

Acquired Immunodeficiency Syndrome

Changes in alpha-1 and beta-2 adrenoceptor density in human hepatocellular carcinoma.

Catecholamines are involved critically in the mechanisms of liver cell proliferation by acting on hepatic alpha-1 and beta-2 adrenoceptors. To identify the role of these receptors in human hepatocellular carcinoma (HCC), the density was examined of alpha-1 and beta-2 adrenoceptors with their affinity and coupling of beta-2 adrenoceptors to adenylate cyclase in HCC tissue and in nonadjacent/nontumor tissue from the same livers. Studies were also done on healthy livers from age-matched and sex-matched patients undergoing abdominal surgery for nonhepatic diseases. Twenty-two HCC had a decrease of about 72% in alpha-1 adrenoceptor density compared with their nonadjacent/nontumor tissue and a decrease of about 40% compared with healthy controls. Nonadjacent/nontumor tissue from HCC patients had a 125% increase in alpha-1 adrenoceptor density compared with healthy livers. Twenty-three of 24 HCC had an increase of about 180% in beta adrenoceptor density compared with their nonadjacent/nontumor tissue and healthy controls. Beta adrenoceptors were coupled to adenylate cyclase, as evidenced by a guanosine triphosphate-mediated right shift in (-)-isoproterenol competition isotherms and by cyclic adenosine monophosphate (cAMP) production after stimulation with (-)-isoproterenol. The HCC tissue yielded a larger increase in cAMP than nonadjacent/nontumor tissue and healthy controls. The authors conclude that a higher density of alpha-1 adrenoceptors in nonadjacent/nontumor tissue from HCC characterizes the "healthy" part of the liver in HCC patients and that an increase in beta-2 and a decrease in alpha-1 adrenoceptor densities characterize the tumor part of the liver in human HCC.

Adenylyl Cyclases

Effect of propionyl-L-carnitine on L-type calcium channels in human heart sarcolemma.

Propionyl-L-carnitine (PC) protects perfused rat hearts against damage by ischemia-reperfusion. Activation of L-type calcium channel play a role on ischemia-reperfusion damage. Therefore, we studied the effect of PC on some properties of L-type calcium channels in an in vitro preparation from human myocardium sarcolemma (from patients with idiopathic dilated cardiomyopathy). Binding of the L-type calcium channel blockers isradipine [3H]-PN 200-110 (PN) to plasma membrane preparations revealed a single population of binding sites (total number: Bmax = 213 +/- 34 fM/mg protein and affinity: Kd = 152 +/- 19 nM; n = 6). The characteristics of these binding sites were evaluated in the presence and in the absence of Ca2+ and of calcium blockers (D-888, a verapamillike drug, and diltiazem). Incubation in a Ca2(+)-containing buffer increased the affinity of PN binding sites. Binding sites for PN were modulated by organic calcium channel blockers; in competition isotherms at 37 degrees C, D-888 (desmethoxyverapamil) decreased the PN binding, whereas diltiazem increased it. These results strongly suggest that the site labelled by PN is the voltage-operated calcium channel of the human myocardium. The addition of PC (1 mM) to plasma membranes labelled with PN at 37 degrees C decreased the affinity of the binding; this effect was counteracted by the addition of Ca2+ to the medium. This result was consistent with a competition between Ca2+ and PC. The effect of PC incubation at 4 degrees C was the opposite; at this temperature PC increased the affinity of the binding sites and the effect was obscured by Ca2+.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites

Alpha 1 adrenoceptor subtype mediates noradrenaline induced contraction of the human internal mammary artery: radioligand and functional studies.

STUDY OBJECTIVE: The aim was to evaluate the characteristics of alpha adrenergic binding sites on human internal mammary arteries and the alpha adrenoceptor mediated vasoconstrictor response to catecholamines. DESIGN: Human internal mammary arteries were cut longitudinally, the intimal layer was scraped, and the arteries homogenised and centrifuged at 50,000 g to obtain a membrane pellet. Saturation isotherms with [3H]-prazosin were done with 50-100 micrograms plasma membranes per tube and increasing concentrations of [3H]-prazosin (non-specific binding: 2.5 mM noradrenaline plus superoxide dismutase and catalase). Kinetic isotherms were done with 100 micrograms plasma membranes and 1-5 nM [3H]-prazosin for time periods ranging from 1 to 90 min; at the equilibrium, dissociation of [3H]-prazosin was achieved by 10 microM prazosin. alpha 2 Adrenoceptor density on internal mammary artery membranes was assessed with [3H]-rauwolscine (non-specific binding: 1 microM yohimbine). Separation of membrane bound radioactivity was achieved by rapid vacuum filtration through Whatman GF/C fibre filters. Saturation isotherms were evaluated by Scatchard plots and kinetic data, and competition isotherms by Enzfitter analysis. Contractility studies were done with helical strips of artery (without adventitial layer) placed in a thermostated perfusion bath. Data were obtained in the presence of different concentrations of agonists and antagonist to obtain Schild plots. Antagonist drugs were employed at only one concentration for each preparation. SUBJECTS: Mammary arteries were collected from 51 patients (age range 42-65 years) undergoing surgery for coronary grafting. MEASUREMENTS AND MAIN RESULTS: The binding of [3H]-prazosin to arterial plasma membrane was rapid and reversible. The K + 1 was 0.13 (SD 0.03) X 10(9) M.min-1 (n = 5) and the Kd, determined as a ratio between k-1/K + 1, was 0.34(0.01) nM (n = 5). [3H]-Prazosin binding, displaceable by 2.5 mM (-)-noradrenaline, was saturable and disclosed an alpha 1 adrenoceptor density of 30(3) fmol.mg-1 protein with a dissociation constant (Kd) of 215(50) pM (n = 18). The adrenergic agonists competed with [3H]-prazosin in the following order of potency: (-)-adrenaline [Ki = 0.6(0.1) microM; n = 5] greater than (-)-noradrenaline [Ki = 1.05(0.015) microM; n = 12] much greater than (-)-isoprenaline [Ki = 150(10) microM; n = 4]. Specific binding of [3H]-rauwolscine to IMA plasma membranes was negligible (about 2 fmol.mg-1 protein) (n = 15) with an unfavourable ratio of non-specific v specific binding. Catecholamines induced a dose dependent contractile response in arterial strips; (-)-noradrenaline: EC50 = 0.48(0.12) microM, n = 20; (-)-adrenaline: EC50 = 0.15(0.16) microM, n = 10; and methoxamine, a selective alpha 1 adrenergic agonist: EC50 0.67(0.15) microM, n = 10. The alpha 2 adrenoceptor agonists BHT-933, BHT-920, and guanabenz did not contract the arterial strips (up to 10 mM). Prazosin (0.03-0.1 microM) produced concentration dependent right shifts of the (-)-noradrenaline [pA2 = 9.83(0.11), n = 19], (-)-adrenaline [pA2 = 9.50(0.31), n = 10], and methoxamine [pA2 = 8.96(0.18), n = 10] concentration-response curve. CONCLUSIONS - Internal mammary artery plasma membranes possess alpha 1 adrenoceptors which are involved in the vasoconstrictor response to catecholamines. alpha 2 Adrenoceptors seem not to be involved.

Adult

Beta-adrenergic receptors and reflex tachycardia after single and repeated felodipine administration in essential hypertension.

To verify the possible contribution of beta-adrenergic receptor down-regulation to the reversal of reflex tachycardia during chronic treatment with a dihydropyridine calcium antagonist, 11 hypertensive patients were studied with noninvasive blood pressure (BP) and heart rate (HR) monitoring after a placebo period, and on the first and seventh day of felodipine administration, 5 mg twice daily. Plasma catecholamines and neutrophil beta-adrenergic receptors were measured on the first and seventh day of treatment, immediately before and 2 h after drug administration. The first administration of felodipine was followed by a significant drop in BP (peak reduction in mean BP 24 +/- 7 mm Hg), lasting 6 h and mirrored by reflex tachycardia (peak increase in HR 14 +/- 9 beats/min). On the morning of the seventh day, 12 h after the previous felodipine administration, mean BP (MBP) was 16 mm Hg lower than on the last placebo day, while HR was unchanged. The next administration of felodipine was followed by a smaller drop in BP (MBP - 15 +/- 7 mm Hg; NS vs. placebo), while reflex tachycardia was the same as after acute felodipine (HR 13 +/- 8 beats/min; p less than 0.05 vs. placebo, NS vs. acute administration). Plasma noradrenaline concentration increased after both acute and chronic administration (p less than 0.0001), and preadministration values were highest on day 7 (p less than 0.05). Neutrophil beta-adrenergic receptor density and affinity did not change either acutely or chronically. This study gives both indirect and direct evidence that beta-adrenoceptor down-regulation does not occur during repeated felodipine administration in hypertension. Reflex tachycardia is not abolished, but is reset to lower BP levels.

Adult

Sympathetic skin response versus maximum motor and sensory conduction velocity to detect subclinical neuropathy in non-insulin-dependent diabetics.

Conventional motor (MCV) and sensory conduction velocity (SCV) of the ulnar (UN), peroneal (PN) and median nerves (MN) and the areas of sympathetic sudomotor response (SSR) recorded from the middle finger were measured on both sides in 20 normal and 20 non-insulin-dependent diabetic (NIDD) subjects. Conventional statistical tests (t test, linear correlation coefficient r) and discrimination analysis were applied to the above electrophysiological parameters. To evaluate the capability of the tests to separate NIDD diseased from normal nerves, the results were represented as generalized distances, i.e., difference between mean discriminant normalized combinations adjusted for intra-group variability. The r values were 0.92 (P less than 0.01) for the UN, 0.40 (P greater than 0.05) for the PN, and 0.86 (P less than 0.01) for the MN sensory action potential (SAP) amplitudes. No significant differences were found for normalized latencies. The r values of the SSR areas were 0.62 (P less than 0.01) at the right and 0.77 (P less than 0.01) at the left, homolaterally to the side of stimulation. SR and MCV generalized distances were 1.35 and 1.39, respectively. The discriminating power of SSR, MCV and SCV considered together was higher (2.40) than that of MCV and SCV (1.70). Since motor, sensory and autonomic alterations often did not coexist in NIDD, it was possible to find at least one type of involvement in most of the diabetic subjects.

Adult

Effects of a cable car trip on blood pressure and cardiovascular hormones in lowlander and highlander normotensives.

The effects of a cable car trip from 1370 m (4500 ft) to 3460 m (11350 ft) were studied in 6 lowlanders (3 men and 3 women, mean age 31 +/- 4 years, living at an altitude of less than 500 m) and in 10 highlanders (all males, mean age 37 +/- 12 years, ski teachers and cable car workers working for greater than or equal to 6 months/year at a greater than 3000 m). Cuff blood pressure (BP), heart rate, plasma catecholamines, serum renin, aldosterone, ACTH and cortisol were measured immediately before and 20 min after the trip, at rest and at the same air temperature. A handgrip test was also performed under the same conditions. At baseline, lowlanders and highlanders showed significant differences in diastolic BP (86 +/- 5 mmHg in lowlanders and 91 +/- 4 mmHg in highlanders, p = 0.05), plasma noradrenaline (323 +/- 114 pg/ml in lowlanders and 585 +/- 255 in highlanders, p less than 0.05), serum renin (10 +/- 6 pg/ml in lowlanders and 17 +/- 8 in highlanders, p less than 0.05), and serum cortisol (163 +/- 54 ng/ml in lowlanders and 120 +/- 25 in highlanders, p less than 0.01). The acute exposure to high altitude did not modify BP, heart rate or any of the measured cardiovascular hormones in either group. The handgrip test provoked a significant increase in systolic and diastolic BP in both lowlanders and highlanders (p less than 0.01), and this response was not modified by the change in altitude; however, highlanders showed significantly smaller increases in systolic BP than lowlanders at both altitudes (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization

Evidence that cholinergic receptors of muscarinic type may modulate vasopressin release induced by metoclopramide.

Studies were carried out in the rat in order to investigate whether cholinergic mechanisms may be involved in vasopressin (VP) release induced by metoclopramide (MCP). The intravenous injection of MCP induced dose-related increases in plasma VP levels in water-loaded rats. These effects were prevented by atropine sulphate, but not by pirenzepine hydrochloride indicating that activation of cholinergic receptors of M-2 type was possibly required for the biologic response.

Animals

Respiratory-burst stimulants desensitize beta-2 adrenoceptors on human polymorphonuclear leukocytes.

We investigated the effect of respiratory-burst stimulants on beta-2 adrenoceptors in human polymorphonuclear leukocytes (PMNL). Pre-incubation of PMNL with these substances did not affect the number or affinity of the receptors but desensitized them, as shown by the "right-shift" in (-)-isoproterenol competition isotherms. H-7, an established protein kinase C inhibitor, and nimesulide, a new putative inhibitor of this enzyme, blunted both superoxide anion production and beta-2 adrenoceptor desensitization. A positive correlation was found between superoxide anion generation and the "right-shift" in isoproterenol competition isotherm (r = 0.92; p less than 0.01). Desensitization of beta-2 adrenoceptors was not due to superoxide anions per se since incubation of PMNL with superoxide anion scavengers (superoxide dismutase and catalase) did not modify the results.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine

Role of the Frank-Starling mechanism in maintaining cardiac output during increasing levels of treadmill exercise in beta-blocked normal men.

To determine the effects of beta blockade on hemodynamics during increasing levels of treadmill exercise, 10 healthy volunteers were studied after 1 week of placebo, and then after 1 week of treatment with oral propranolol, 80 mg twice daily, or dilevalol, 400 mg once daily. The study was randomized and double-blind, with a crossover sequence. Hemodynamics were measured by CO2 rebreathing at rest and at 25, 50, 75 and 100% of VO2 max. After placebo, cardiac output increased from 5.8 +/- 2.1 (rest), to 19.4 +/- 6.4 liters/min (100% VO2 max), mainly due to an increase in heart rate from 84 +/- 6 to 169 +/- 15 beats/min. Stroke volume increased from 70 +/- 27 (rest), to 137 +/- 65 ml (25% VO2 max), and then leveled off to 116 +/- 41 at 100% VO2 max. After both beta blockers, exercise cardiac output was maintained at 100% VO2 max: 20.1 +/- 9.3 liters/min with propranolol and 19.1 +/- 8.6 with dilevalol. However, a significant reduction versus placebo values was observed for cardiac output at 25% VO2 max, from 13.7 +/- 5.9 during placebo, to 9.4 +/- 2.5 during propranolol, and to 9.6 +/- 2.3 during dilevalol (both p less than 0.01 vs placebo). Maintenance of cardiac output with both beta blockers at higher levels of exercise came from an increased stroke volume (p less than 0.05 vs placebo), while heart rate (in beats/min) was greatly reduced (propranolol 61.6 +/- 9.4 rest, 90.1 +/- 10.7 at 100% VO2 max; dilevalol 70.8 +/- 6.4 rest, 99.2 +/- 11.8 at 100% VO2 max, p less than 0.01 vs placebo for each).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists

Interaction of selected vasodilating beta-blockers with adrenergic receptors in human cardiovascular tissues.

beta- And alpha 1-adrenoceptor antagonist properties of bufuralol, carvedilol, celiprolol, dilevalol, labetalol, and pindolol were investigated in human myocardium and mammary artery using binding techniques and functional studies. In myocardial membranes, beta-adrenoceptor antagonists showed monophasic competition isotherms for [125I]pindolol binding with high affinity (Ki from 1-100 nM), except for celiprolol which displayed a biphasic competition isotherm (pKi = 6.4 +/- 0.06 for beta 1- and 4.8 +/- 0.07 for beta 2-adrenoceptors). Drug interactions with alpha 1-adrenoceptors were evaluated in human mammary artery by [3H]prazosin binding and by measuring contractile responses to norepinephrine (NE). Labetalol and carvedilol showed a moderate affinity for alpha 1-adrenoceptors (pKi = 6.2 +/- 0.01 and 6.1 +/- 0.06, respectively), and inhibited NE-induced contractions (pA2 = 6.93 +/- 0.23 and 8.64 +/- 0.24, respectively). Dilevalol, bufuralol, and pindolol displayed weak effect both in binding (Ki in micromolar range) and functional experiments (pA2 = 5.98, 5.54, and 6.23, respectively). Celiprolol did not show antagonist properties up to 100 microM in functional studies, but displayed a slight affinity for alpha 1-adrenoceptors in binding studies. The data indicate that the vasodilating activity of these beta-adrenoceptor antagonists is caused in some instances by an alpha 1-adrenoceptor antagonism (labetalol, carvedilol), whereas for the others alternative mechanisms should be considered.

Adrenergic beta-Antagonists

Identification of alpha 1-adrenergic receptors on sarcolemma from normal subjects and patients with idiopathic dilated cardiomyopathy: characteristics and linkage to GTP-binding protein.

Discontinuous density sucrose gradient centrifugation was used to isolate membrane vesicles from the left ventricle of three normal subjects (one prospective organ donor and two traffic victims whose hearts were obtained 1 hour after death) and nine patients undergoing cardiac transplantation as a consequence of idiopathic dilated cardiomyopathy. Sarcolemma-enriched subcellular fractions, detected in the interface between 8.55% and 25% sucrose, were identified by the increased activity of Na+,K+-ATPase and by enrichment in beta-adrenergic receptor density. The density of beta-adrenergic receptors was lower in vesicles from diseased hearts (610 +/- 71 fmol/mg protein) than in vesicles from normal hearts (1,410 +/- 226 fmol/mg protein; p less than 0.01). alpha 1-Adrenergic receptors were identified in these membrane vesicles by [3H]prazosin binding. Specific binding of [3H]prazosin was about 50% of the total binding at 1 nM, and alpha 1-adrenergic binding sites were saturable at approximately 3 nM. Scatchard analysis revealed 58 +/- 5 fmol/mg protein (KD = 0.90 +/- 0.08 nM) in pathological hearts and 30 +/- 5 fmol/mg protein (KD = 0.90 +/- 0.03 nM) in normal hearts (p less than 0.01). The displacement curve of (-)-norepinephrine in membrane vesicles from normal hearts delineated one subpopulation of alpha 1-adrenergic receptors; the addition of 0.1 mM GTP did not cause right shift. In membrane vesicles from diseased heart, the displacement curve of (-)-norepinephrine disclosed two subpopulations of alpha 1-adrenergic receptors. A right shift that occurred after addition of GTP showed that in this case alpha 1-adrenergic receptors were functionally coupled with GTP-binding protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult

Aspirin stimulates insulin and glucagon secretion and increases glucose tolerance in normal and diabetic subjects.

Normal subjects and patients with adult-onset diabetes received 10 gm. of aspirin in four days. On the fourth day, the fasting serum glucose and the glucose response to oral glucose were decreased in both groups. These changes were associated with increased levels of serum insulin and pancreatic glucagon, although the glucagon responses to oral glucose were unchanged. In the diabetic patients, aspirin therapy was followed by a decreased glucose response to I.V. glucose and by the appearance of an early insulin peak, which could not be demonstrated before treatment. Aspirin did not affect the I.V. glucose tolerance in normal subjects, although it did enhance the early insulin peak. A decrease in the fasting levels of free fatty acids was noted in both groups, whereas the fasting level of triglycerides decreased only in the diabetic patients. Cholesterolemia did not change in either group. A few preliminary observations indicate that, in normal subjects, ibuprofen and ketoprofen, two other presumed prostaglandin inhibitors, did not affect fasting glycemia, glucose tolerance, or the insulin response to glucose. No changes were noted after the administration of placebo.

Adult