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Biomedical subjects

R Caldara

Publications and source records attributed to R Caldara.

At least 55 records · Page 3Linked to original sources
PubMed1986

Long-lasting prolactin-lowering effect of cabergoline, a new dopamine agonist, in hyperprolactinemic patients.

The new long-acting ergoline derivative cabergoline was given orally in a single dose of 300 micrograms to 15 hyperprolactinemic patients (including 4 acromegalic patients, 2 of whom were dopamine responsive). Serum PRL and GH levels were determined before and 3, 4, and 6 h and 1, 2, 3, 4, 5, 6, and 7 days after treatment. A control test with a single oral dose of 2.5 mg bromocriptine was also performed; serum PRL and GH levels were measured at the same time intervals for 2 days. Cabergoline induced a marked fall in serum PRL which began within 3 h and continued for 7 days. The maximal decrease ranged between -49.2% and -55.2% and occurred after 2-5 days. This maximal effect was only slightly less than that 6 h after bromocriptine treatment (-63.8%). After cabergoline treatment, serum GH levels did not change significantly in either nonacromegalic or acromegalic patients, whereas the two dopamine-responsive acromegalic patients had a marked GH fall after bromocriptine. A moderate blood pressure decrease, more evident in the standing position, occurred after both cabergoline and bromocriptine treatments. The only symptomatic side-effect was orthostatic hypotension after cabergoline in an elderly woman. These data indicate that cabergoline has potent and prolonged dopaminergic activity and may prove suitable for once weekly treatment of hyperprolactinemic patients.

Adult↗
PubMed1985

Effect of nifedipine on gastric acid secretion and gastrin release in healthy man.

Nifedipine, a calcium-channel antagonist widely used in cardiovascular disease, has recently been reported to be effective in the treatment of oesophageal motor disorders. The effect of a single therapeutic dose of nifedipine (20 mg p.o.) has been evaluated on basal and submaximal pentagastrin-stimulated gastric secretion and meal-stimulated gastrin release in healthy man. In comparison with placebo, nifedipine significantly decreased both basal and stimulated gastric acidity and juice volume, whereas only a slight but insignificant reduction in meal-stimulated gastrin levels was observed after drug administration. The results are in agreement with previous reports that calcium is involved in stimulus-secretion coupling in the human parietal cell. They do not confirm the effect of calcium on G-cells, although it is likely that doses of nifedipine higher than those commonly used might be effective in the reduction of gastrin secretion.

Adult↗
PubMed1985

Effect of L-dopa with and without inhibition of extra cerebral dopa decarboxylase on gastric acid secretion and gastrin release in man.

The present study was undertaken to investigate the possibility that central nervous system monoaminergic pathways may play a role in the control of gastric acid and gastrin secretion in man. Submaximal pentagastrin stimulated (0.25 micrograms/kg/h) gastric acid secretion, as well as basal gastrin concentrations were studied in two groups of subjects. The first group received oral administration of placebo and the catecholamine precursor L-dopa (500 mg); the second group was treated with placebo and the association of L-dopa (100 mg) plus carbidopa (35 mg) after pretreatment with carbidopa (50 mg every six hours for four doses), a schedule which is known to increase brain catecholamine concentrations. In comparison with placebo, stimulated gastric acid secretion was reduced by L-dopa alone, whereas was not modified by L-dopa plus carbidopa. Basal gastrin concentrations were increased after L-dopa and after L-dopa plus carbidopa. These data show that basal gastrin concentration is raised by central catecholamine augmentation; but gastric acid secretion seems to be influenced by changes of peripheral catecholamine concentrations. It is suggested that dopamine and perhaps noradrenaline, but not adrenaline, are important in these effects.

Adult↗
PubMed1984

Lack of effect of cimetidine on the renin-angiotensin-aldosterone system in man.

It is widely accepted that angiotensin II, ACTH and potassium are the major factors controlling the release of aldosterone. Conflicting results have been reported about the role of serotonin, dopamine and histamine. To evaluate the possible involvement of H2-histaminergic receptors, the effect of intravenous injection of 400 mg cimetidine on the renin-angiotensin-aldosterone system has been evaluated in 10 healthy volunteers. The administration of cimetidine did not induce a significant change in plasma aldosterone level or in its major controlling factors.

Adult↗
PubMed1984

Lack of effect of domperidone on gastrin release: evidence for a peripheral activity of the drug.

The effect of intravenous administration of domperidone, a dopamine receptor antagonist with peripheral activity, on basal and submaximal pentagastrin-stimulated gastric acid secretion and gastrin release has been evaluated in healthy volunteers. No significant changes were observed in the parameters studied. The lack of effect on gastrin release appears to confirm that domperidone is unable to penetrate the blood brain barrier in appreciable amounts in adults.

Adult↗
PubMed1984

Serum prolactin and ovarian function after discontinuation of drug treatment for hyperprolactinaemia: a study with bromocriptine and metergoline.

Serum prolactin (PRL) was estimated for up to 2 months after discontinuation of therapy with either bromocriptine (n = 33; 15 with idiopathic disease, 12 with pituitary microadenoma, and six with macroadenoma) or metergoline (n = 23; 11 with idiopathic disease, and 12 with microadenoma) that had been administered for 8-30 months. Only five patients treated with bromocriptine and two treated with metergoline had PRL levels that remained normal or below 50% of pretreatment values. Among the patients followed-up for up to 12 months, four showed a fall in PRL at 3-4 months, but this was followed by a rise in one patient. Five patients showing persistently lower or normal PRL after drug withdrawal were retested with thyrotrophin-releasing hormone; the two responsive women also had a normal response before treatment. Of 10 patients followed for 9 months, three had persistently normal PRL levels. Amenorrhoea and anovulation recurred, with some delay, in all the patients showing PRL rebound except one. Medical treatment of hyperprolactinaemia only rarely results in permanent benefit.

Adenoma↗
PubMed1983

Effect of sulpiride isomers on gastric acid and gastrin secretion in healthy man.

The effects of the antidopaminergic drug sulpiride on gastric acid secretion and gastrin release have been evaluated in 42 healthy individuals. Basal and submaximal pentagastrin (0.5 micrograms/kg-h)-stimulated gastric acid secretion, as well as basal and meal-induced gastrin secretion, were studied after acute intramuscular administration of racemic sulpiride (100 mg) and its L-(50 mg) D-(50 mg) isomers. Racemic and L-sulpiride significantly decreased stimulated serum gastrin concentration, but they did not affect fasting serum gastrin or basal and stimulated gastric acidity. D-sulpiride significantly decreased gastric acid secretion, without affecting serum gastrin levels. While the effects of racemic and L-sulpiride are analogous to those of other antidopaminergic drugs, D-sulpiride mimics the action of dopamine, at least at gastric level. These data support the hypothesis that the D-isomer may possess agonist-antagonist activity at dopamine receptors. Since racemic sulpiride has been used with conflicting results in the therapy of patients with peptic ulcer, in the light of the present results it would be of interest to study separately the efficiency of the D- and L-isomers of the drug in healing peptic ulcer.

Adult↗
PubMed1983

Effects of ibopamine on serum prolactin and growth hormone levels in hyperprolactinemic and acromegalic subjects.

The effects of oral doses (100, 200, and 400 mg) of a dopamine derivative, ibopamine, on serum prolactin (PRL) and growth hormone (GH) levels were evaluated in hyperprolactinemic patients, some of whom also were acromegalic. There was dose-related lowering of PRL levels. The highest dose was as effective as 500 mg L-dopa, although the duration of action was shorter, with a decrease to below 50% of basal PRL values in all patients. Serum GH did not rise in nonacromegalic subjects, but it fell after 400 mg ibopamine in the L-dopa-sensitive acromegalic patients. These data suggest, but do not prove, that ibopamine is able to directly stimulate pituitary dopamine receptors.

Acromegaly↗
PubMed1983

Dopaminergic control of gastric acid and gastrin secretion in man: lack of effects after acute oral administration of ibopamine, an analogue of dopamine.

The effect of oral administration of the dopaminergic drug, ibopamine, at the dose of 200 mg and 400 mg, on basal and submaximal pentagastrin (0.25 microgram kg-1 h-1) stimulated gastric acid secretion as well as basal serum gastrin concentration has been evaluated in 24 healthy individuals. In comparison with placebo no significant changes were observed in all the variables studied. The lack of effects on gastric acid secretion might be due to a selective stimulation of dopaminergic receptors not active in the regulation of gastric acidity or not present in gastric mucosa, while unchanged serum gastrin secretion is possibly due to a poor crossing of blood-brain barrier by ibopamine.

Adult↗
PubMed1983

Effect of fenfluramine on prolactin secretion in obese patients: evidence for serotoninergic regulation of prolactin in man.

The present investigation was carried out to study the effect of serotoninergic stimulation on prolactin (PRL) secretion in man. Fenfluramine (60 mg, orally), an anorexiant drug which under acute circumstances stimulates the serotoninergic system, was administered to eight obese patients. Compared with placebo, drug administration increased PRL significantly (P less than 0.05 at 180 and 300 min, P less than 0.01 at 240 min). No significant changes were observed after fenfluramine in blood pressure, plasma aldosterone (PA), plasma cortisol, plasma renin activity, serum electrolytes or growth hormone. Since it has been reported that dopaminergic blockade raises PA concentration, the lack of change in PA in obese patients treated with fenfluramine suggests that the observed increase in PRL induced by fenfluramine is likely to be mediated by serotoninergic stimulation.

Adult↗
PubMed1983

Thyroid function tests in chronic liver disease: evidence for multiple abnormalities despite clinical euthyroidism.

To further evaluate thyroid function in patients with liver disease, we have measured total and free T3 and T4, thyroxine binding globulin, basal and thyrotropin releasing hormone-stimulated thyrotropin and thyroglobulin antibodies in 33 patients with liver cirrhosis, in 22 with chronic hepatitis and in 30 healthy controls. All the patients but one were clinically euthyroid. T3, FT3, T3/thyroxine binding globulin and T4/thyroxine binding globulin ratios and thyrotropin after thyrotropin releasing hormone were significantly reduced, while FT4, thyroxine binding globulin and thyrotropin were significantly increased in liver cirrhosis. In chronic hepatitis group, FT3 and T3/thyroxine binding globulin ratio were significantly lower and thyroxine binding globulin and FT4 were higher than in healthy controls. The between patients comparison revealed a significantly lower T3, FT3, T3/thyroxine binding globulin and T4/thyroxine binding globulin ratios and delta thyrotropin in cirrhotics. Thyroglobulin antibodies were present at high titre only in two patients one of whom having evidence of Hashimoto's thyroiditis with subclinical hypothyroidism. The correlation coefficient between T4/thyroxine binding globulin ratio and FT4 were lower in patients than in controls. Furthermore an abnormal thyrotropin response to thyrotropin releasing hormone was shown in 10 cirrhotics and in four patients with chronic hepatitis. Serum T3 significantly correlated with serum bilirubin, albumin, and prothrombin time in both groups of patients. The present data confirm the existence of several abnormalities of thyroid function tests in patients with chronic liver disease, although showing that euthyroidism is almost always maintained, probably as a result of low-normal FT3 and high-normal FT4. Furthermore, T3 serum levels appear to parallel the severity of liver dysfunction.

Adult↗
PubMed1982

Prolactin stimulation by intravenous labetalol is mediated inside the central nervous system.

We have previously reported that labetalol infusion increases prolactin (PRL) secretion in hypertensive patients. In an attempt to investigate the site where labetalol stimulates PRL, the drug was infused intravenously (100 mg) into healthy subjects, both under basal conditions and after pretreatment with L-dopa plus carbidopa (250 mg and 25 mg respectively every 6 h for 1 day), since this regimen has been reported to blunt the PRL responses to centrally acting stimuli. The effects of oral labetalol administration (100 and 200 mg) on PRL was also evaluated. Serum PRL concentration did not change after oral labetalol, whereas it was increased by intravenous drug administration. This effect was completely abolished by pretreatment with L-dopa plus carbidopa. These findings, though they do not demonstrate the mechanism, suggest that the hyperprolactinaemia induced by labetalol is mediated inside the blood-brain barrier.

Administration, Oral↗
PubMed1982

Functional characterization of hypothalamic hyperprolactinemia.

PRL secretory dynamics were evaluated by several stimulation and suppression tests in nine patients with hyperprolactinemia due to organic hypothalamic disease. Basal PRL levels ranged between 20-63 ng/ml. There was a normal PRL response to TRH in eight cases (i.e. doubling of basal levels), whereas none of the seven tested subjects responded to sulpiride. The same dissociation of responses was not observed in any of the patients who were still hyperprolactinemic after surgery. Concomitant dopamine infusion resulted in sulpiride-induced PRL release in the four subjects so studied. None of 50 other hyperprolactinemic patients (11 with macroprolactinoma, 18 with microprolactinoma, and 21 with idiopathic hyperprolactinemia) showed PRL response to TRH but not to sulpiride. The TRH-induced PRL increase was significantly higher than that induced by sulpiride in hypothalamic hyperprolactinemia and significantly lower in idiopathic disease as well as in healthy controls; no differences were found in prolactinoma patients. The administration of substances resulting in stimulation of pituitary dopamine receptors, such as dopamine and L-dopa, induced a normal PRL suppression in 7 patients with hypothalamic disease so tested, whereas central nervous system-acting dopaminergic drugs, such as carbidopa plus L-dopa and nomifensine, failed to lower PRL levels in most cases (even when normoprolactinemic after surgery). These data suggest that the mild to moderate hyperprolactinemia found in many patients with hypothalamic lesions is due to dopamine deficiency at the pituitary level, that TRH and dopamine receptors at the lactotropes are intact in this condition, and that paired TRH and sulpiride tests may be of some diagnostic utility in hyperprolactinemic patients. They further suggest that subjects with so-called idiopathic hyperprolactinemia do not suffer from the type of hypothalamic derangement exhibited by patients with organic lesions of the hypothalamus.

Adult↗
PubMed1981

Effects of chronic prazosin treatment on the renin-angiotensin-aldosterone system in man.

The effects of chronic prazosin treatment (3 mg/day for three weeks) on plasma renin activity (PRA) and plasma aldosterone (PA) levels were evaluated in 12 hypertensive patients, under conditions of metabolic balance. After three weeks of drug administration no significant change occurred in PRA as well as PA levels, with respect to pretreatment values, both in basal conditions and following 2 hours of ambulation. No change was observed in heart rate, while a fall in both systolic (P less than 0.02) and diastolic (P less than 0.05) blood pressure occurred in supine as well as in deambulation-stimulating condition. A mild increase in body weight (P less than 0.05) and a decrease in serum sodium (P less than 0.05) was induced by prazosin treatment. These findings are in keeping with the pharmacologic properties of prazosin, which is a selective blocker of postsynaptic alpha adrenoreceptors and therefore lowers vascular resistance without reflex sympathetic overactivity. The moderate volume expansion after prazosin does not appear to be aldosterone mediated.

Adult↗
PubMed1981

Effect of loperamide, a peripheral opiate agonist, on circulating glucose, free fatty acids, insulin, C-peptide and pituitary hormones in healthy man.

The effect of acute oral administration of loperamide (4, 8 and 16 mg), a peripheral opiate agonist used in the treatment of diarrhoea, on several metabolic and endocrine variables has been evaluated in healthy volunteers in comparison with placebo. Plasma glucose was significantly raised by all three doses, whereas serum IRI and C-peptide were decreased and serum FFA was significantly increased only after loperamide 8 and 16 mg; serum PRL, GH, LH and FSH did not change. The data suggest that opiates may be involved in the regulation of glycaemia, probably by modifying islet hormone secretion by acting at a peripheral site, since loperamide does not cross the blood-brain barrier. Although the precise mechanism of these actions is unknown, it is suggested that the effects of loperamide are mediated either by stimulation of opiate receptors per se, or by suppression of acetylcholine release from cholinergic nerve endings. The lack of change in pituitary hormone secretion by loperamide is in agreement with previous observations indicating that opiate effects on PRL, GH and gonadotropins occur at the level of the central nervous system.

Adult↗