Structural organization and chromosomal localization of the human type II deiodinase gene

OBJECTIVE

The selenoenzyme type 2 iodothyronine 5' deiodinase (DII) catalyzes the conversion of thyroxine into its active form tri-iodothyronine (T3), modulating thyroid hormone homeostasis in a local, tissue-specific manner. The amphibian, rodent and human cDNAs encoding this enzyme have been recently cloned and expressed. At present, little information regarding the genomic structure of mammalian DII is available.

DESIGN AND METHODS

The complete structure, including intron-exon junctions, of the human DII (hDII) gene was obtained by long PCR and rapid amplification of cDNA ends (RACE). Chromosomal assignment of the hDII gene was performed by fluorescence in situ hybridization using a highly specific probe.

RESULTS AND CONCLUSIONS

Our data demonstrated that hDII is a single copy gene located on chromosome 14, position 14q24.3. The gene spans over 15 kb, and the 7 kb transcript is encoded by three exons of 149 bp, 273 bp and 6.6 kb separated respectively by two 274 bp and 7.4 kb introns. A restriction map of the hDII gene is also reported. These data will help in further studies of the role of DII in the maintenance of peripheral thyroid hormone homeostasis.

Effect of tryptophan on the early tri-iodothyronine uptake in mouse thymocytes

OBJECTIVE

We have studied the effect of tryptophan on cellular [(125)I]tri-iodothyronine (T3) uptake by mouse thymocytes.

MATERIALS AND METHODS

Mouse thymocytes (20 x 10(6 )cells/ml) were suspended in Krebs-Ringer solution buffered by Tris-HCl and incubation (23 degrees C at pH7.45+/-0.6), in the presence or absence of 1mM tryptophan, was started by adding 25 pM [(125)I]T3. At the end of incubation, samples were cooled in ice, centrifuged over a 30% sucrose cushion and the cell-associated radioactivity was measured in the pellet.

RESULTS

Tryptophan reduced both the total and the saturable fraction of [(125)I]T3 uptake by 44% (P=0.0009) and 60% (P=0.0006) respectively, following 1 min of incubation. This effect was specific and dose-dependent, being maximal at 5mM concentration (-82%). In contrast, the pre-exposure of cells to tryptophan for up to 2h had no effect on the subsequent uptake of [(125)I]T3, in the absence of tryptophan. The effect of D-tryptophan on saturable T3 uptake was not different from that obtained using the L-stereoisomer. Tryptophan reduced the V(max) of the initial rate of saturable [(125)I]T3 uptake by two-thirds without affecting the apparent K(m) (2.2 nM) of the process, thus indicating the non-competitive nature of the inhibition. In sodium-free medium the saturable [(125)I]T3 uptake was reduced by 43%. The inhibitory effect of tryptophan on [(125)I]T3 uptake was exerted in both the presence and the absence of sodium. In fact, the inhibitory effect of tryptophan on T3 transport was greater and significantly different (P=0.0046) from that obtained by sodium depletion alone.

CONCLUSIONS

Tryptophan interferes with both the sodium-dependent and -independent components of [(125)I]T3 uptake by a dose-dependent, non-competitive mechanism which operates in cis-modality at the plasma membrane level of mouse thymocytes.

Isolation of human type 2 deiodinase gene promoter and characterization of a functional cyclic adenosine monophosphate response element

We analyzed the structure and function of the 5' flanking region of the human type 2 deiodinase (hD2) gene. Two major transcription start sites were identified at -470/-474 from the ATG. The 5' flanking region of hD2 gene efficiently directed transcription in transient transfection studies, using luciferase as reporter gene, in HEK 293 cells. Basal transcriptional activity was significantly reduced by deleting the region containing a canonical cAMP-responsive element (CRE) located -766/-759 from ATG. Forskolin treatment significantly increased luciferase activity in cells transfected with CRE-containing constructs. This effect was abolished in constructs that did not contain CRE or contained the mutagenized CRE. Northern blot analysis in JEG-3 cells revealed that the hD2 messenger RNA was markedly increased after stimulation with cAMP agonist. The electrophoretic mobility shift assay with hD2-CRE probe and HEK 293 nuclear extract showed the occurrence of a DNA-protein complex, which was competed by specific unlabeled oligonucleotides and supershifted by the anti-CREB and anti-CRE modulator-1 antibodies. A-CREB, a dominant negative inhibitor of CREB, completely inhibited forskolin induction of the hD2 promoter. CREB protein, once cotransfected with hD2 promoter construct and pKA in F9 teratocarcinoma cells, which are unresponsive to cAMP, was able to stimulate the hD2 gene transcription. These results indicate the existence of a functional promoter within the 5' flanking region of hD2 gene which is characterized by the presence of a CRE. The specific involvement of CREB in the cAMP-mediated hD2 gene promoter induction also has been demonstrated.

Atrophic body gastritis in patients with autoimmune thyroid disease: an underdiagnosed association

BACKGROUND

Atrophic body gastritis (ABG) has never been histologically characterized in patients with autoimmune thyroid disease (AITD), and its prevalence may be substantially different from that previously assessed based on only indirect evidence.

OBJECTIVE

To detect and characterize the presence of ABG in patients with AITD.

METHODS

Sixty-two patients with AITD (5 men and 57 women), aged between 21 and 74 years, have been screened for the presence of ABG by assaying serum gastrin levels. Patients with hypergastrinemia underwent gastroscopy followed by the histological examination of multiple biopsy specimens. The diagnosis of ABG was based on hypergastrinemia and pentagastrin-resistent achlorhydria, confirmed by histological examination.

RESULTS

Twenty-two (35%) of 62 patients had hypergastrinemia (mean +/- SEM gastrin level, 1070+/-288 pmol/L). The diagnosis of ABG has been histologically confirmed in all 22 patients, and the score of atrophy was moderate to severe. In group A (patients aged 20-40 years; n = 21), 6 patients (29%) had ABG, compared with 11 patients (37%) in group B (patients aged 41-60 years; n = 30) and 5 patients (45%) in group C (patients aged 61-80 years; n = 11). Antiparietal cell antibodies were detected in only 68% (15/22) of patients with ABG. Anemia was observed in 82% (18/ 22) of patients with AITD and ABG but only in 22% (9/40) of patients without ABG (P<.0001).

CONCLUSIONS

In the patients with AITD studied, about one third had ABG, which was diagnosed also in young patients; the measurement of gastrin levels represented the most reliable tool in the diagnosis of ABG; and the presence of anemia, even microcytic, was suggestive of undiagnosed ABG.

Genomic characterization of the coding region of the human type II 5'-deiodinase gene

Type II 5'-Deiodinase (5'DII) is a key element in the maintenance of peripheral thyroid hormone homeostasis through the regulation of local T4 to T3 conversion in pituitary, brain, brown adipose tissue and placenta. The cDNA containing the coding region of the human 5'DII (HDII) has been recently cloned from infant brain. In the present paper we report the genomic structure, chromosomal localization and restriction map of the coding region of HDII. The presence of a single intron located at codon 75 was demonstrated using a PCR-based strategy; the exon-intron junctions were then cloned and partially sequenced. Chromosomal localization was performed by radiation hybrid mapping. This study demonstrated that the entire coding region of the HDII gene is contained in two exons spliced at codon 75 by a 7.4 Kb intron and that the HDII chromosomal location is 14q24.3. These data will allow further studies of the role of HDII in the pathophysiology of thyroid homeostasis.

Paroxysmal atrial fibrillation after high-dose melphalan in five patients autotransplanted with blood progenitor cells

Among the drugs used in conditioning regimens for stem cell transplantation, high-dose melphalan (HDM) plays an important role for both its strong myeloablative effect and for its favourable dose-response ratio. Here we report five cases of high frequency atrial fibrillation (AF) developing after HDM. Duration of the arrhythmia was always very short, beginning at variable intervals after the administration of HDM, in the absence of other factors potentially able to trigger AF. In all patients sinus rhythm was restored within 72 h and the follow-up did not show any cardiac damage. To the best of our knowledge, this side-effect has never been reported to occur after HDM.

Circulating levels of adrenomedullin in patients with Addison's disease before and after corticosteroid treatment

BACKGROUND AND OBJECTIVE

A novel hypotensive peptide, adrenomedullin (AM), had recently been isolated, purifed and its encoding gene sequenced from a human phaeochromocytoma. In humans AM circulates in physiological levels and possesses a distinct vasodilatatory activity. The purpose of this study was to examine the behaviour of AM levels in primary adrenal failure.

DESIGN

Plasma AM levels were measured in patients with proven Addison's disease using a specific radioimmunoassay and compared to those in healthy normotensive subjects.

PATIENTS

Eighteen patients with Addison's disease (10 men and eight women; ages 21 to 72 years) and 21 healthy control subjects (13 men and eight women; ages 20 to 71 years) were enrolled in the study. All patients were studied under basal conditions and 10 were reassessed following corticosteroid treatment.

RESULTS

All patients with Addison's disease showed increased levels of AM compared to the control group. Mean plasma AM levels were correspondingly higher in patients with Addison's disease than in normal subjects (102.1 +/- 33.4 (SD) ng/l versus 13.7 +/- 6.1 ng/l; P < 0.0001). In 10 patients studied after corticosteroid treatment, plasma AM levels were significantly reduced (P < 0.0001: 110.3 +/- 35.8 ng/l versus 32.4 +/- 10.3 ng/l) after 2 weeks of treatment. A weak correlation (r = 0.458; P = 0.048) was observed between systolic blood pressure and plasma AM concentrations in all patients with Addison's disease.

CONCLUSIONS

These results indicate a consistent but reversible increase of adrenomedullin in patients with Addison's disease.

Combined impairment of nutritional parameters and thyroid homeostasis in mildly iodine-deficient children

The relation between thyroid homeostasis and the biochemical parameters of subclinical protein malnutrition has been analyzed in schoolchildren in a rural area in the south of Italy, known to be moderately iodine-deficient. The sera of 32 children (15 males and 17 females aged 6 to 11 years) have been analyzed. These children were divided into two groups, according to thyroid function: (1) 16 euthyroid children (mean thyrotropin [TSH] 2.38 +/- .35 mU/L; 6 with goiter) and (2) 16 subclinical hypothyroid children (mean TSH 7.32 +/- 1.68 mU/L; 6 with goiter). Retinol circulating complex (RCC) components were determined in serum by high-performance liquid chromatography (HPLC) and radial immunodiffusion and the essential and nonessential amino acid levels by ion exchange chromatography. Reduced retinol binding protein (RBP) and transthyretin (TTR) levels were recorded in the sera of 11 of 32 (34%) and in 5 of 32 (16%) patients, respectively. The linear regression analysis revealed that RBP and TSH levels were inversely correlated (r = -0.514; p < 0.0026). The RBP levels were subnormal in 2 of 16 euthyroid and in 9 of 16 hypothyroid patients (Fisher test p < 0.023), and the mean RBP levels were significantly reduced in the hypothyroid patients when compared with those of the euthyroid group (p < 0.0026). The retinol/RBP ratio was also significantly different between euthyroid and hypothyroid children (0.75 vs. 0.95; p < 0.0002). The mean essential amino acid levels, with the exception of methionine, were all in the normal range. The selected amino acid ratios confirmed that the patients were exposed to mild protein malnutrition. These results provide evidence that even mild protein-energy malnutrition may have detrimental effects on thyroid homeostasis in iodine-deficient areas.

Diagnosis of thyroid carcinoma

Despite being one of the most frequent neoplasms occurring in the endocrine system, thyroid carcinoma is, nevertheless, a relatively rare event (0.5-1.5% of all malignant tumours in man); the differentiated forms are the most prevalent and are characterized by a high mean survival rate, whereas the very aggressive forms are rare and prognosis is unfavourable. Diagnostic evaluation of carcinomatous lesions, particularly in the early stages, may give rise to considerable difficulties at a clinical level due to the differentiation of the benign lesions, which are a frequent finding. The traditional clinico-semeiological and instrumental parameters, which, in the past, were used in the assessment of suspected malignancy, should not be considered as markers of malignancy; however, exposure to ionizing radiations during childhood may have a well defined role of risk. Following the recent progress in genetic and molecular studies, it is now possible to exploit genetic-molecular tumor markers and, at present, thyroid medullary carcinoma may be identified also in the absence of clinical evidence, particularly the familial form, thus allowing suitable prophylaxis in those subjects with specific genetic impairment (e.g. preventive thyroidectomy in infancy). Since no discriminating clinico-semeiological parameters are available, considering the aspecificity of scintigraphic findings and the lack of reliability of echographic imaging in providing data which enable us to distinguish a rare neoplastic pattern from the more frequent finding of a benign thyroid mass, fine-needle aspiration (FNA) cytology may today be considered the technique of choice in the screening of the thyroid nodule. Our experience in over 12,000 nodular lesions since 1982, has confirmed that the cytological examination is the most discriminating investigation, diagnostic reliability being far greater than that of traditional techniques. Considering the high frequency of thyroid nodule disease which rarely harbours a carcinomatous lesion, a very scrupulous diagnostic algorithm is mandatory. The FNA cytology, together with morphofunctional and immunological examinations, as well as dynamic exploration of the thyroid hypothalamo-pituitary axis, which allows a nosographic picture of the thyroid nodule disease, provides a more discriminating appraisal for the surgical approach to a single, solitary or prominent nodule.

Reversible increase of intraocular pressure in subclinical hypothyroid patients

OBJECTIVE

The aim of the study was to analyse the relationship between the ocular parameters, namely intraocular pressure (IOP), and the early forms of subclinical hypothyroidism.

DESIGN

Fifty-three subjects (9 male and 44 female) aged from 18 to 45 years (mean 32 +/- 7 years) were selected for this study. Twenty-nine met the criteria of subclinical hypothyroidism and 24 euthyroid subjects, age- and sex-matched, were used as controls.

METHODS

All individuals underwent a complete ocular examination, including visual field examination and serial measurement of IOP by means of a Goldmann tonometer. A tonographic examination was also performed.

RESULTS

The hypothyroid patients showed a substantially higher pressure in both eyes compared with control subjects (right eye = 17.52 +/- 4.74 vs 13.42 +/- 1.95 mmHg, P < 0.0001; left eye = 17.55 +/- 3.99 vs 13.71 +/- 1.55 mmHg, P < 0.0001). Indeed, the tonometric pressure exceeded 18 mmHg in 11 out of the 29 (38%) patients in the right eye and in 8 out of 29 (27%) patients in the left eye. The outflow index was normal in all subjects except in two hypothyroid patients. After two months of L-thyroxine (L-T4) replacement therapy, only one patient continued to show tonometric values above 18 mmHg and the hypothyroid patients showed a significant reduction in mean IOP in both eyes compared with pre-treatment values (right eye = 14.96 +/- 1.32 mmHg, P < 0.0097; left eye = 15.03 +/- 1.38 mmHg, P < 0.0018). Treatment did not lead to any change in the outflow indices; however, the C value (outflow coefficient at the sclerocorneal corner) returned to normal in the two patients with increased pre-treatment tonographic values.

CONCLUSIONS

These findings indicate that the intraocular pressure is increased even in subclinical hypothyroid patients and that, at this early stage, the impairment is fully reversible with L-T4 therapy.

[Clinical significance of Hürthle cell in the cytology of thyroid disease]

The natural history of Hürthle cell (HC) lesions has been the focus of a considerable debate. The difficulties in defining the malignant potential of HC has led to the current designation of HC tumor, with the implication that it may behave as either a benign or a malignant lesion. The objective of our study was to verify the clinical and prognostic relevance of the cytological diagnosis of HC in the thyroid lesion, 10,950 consecutive patients (F/M = 5.6/1) with thyroid nodules were evaluated by means of fine needle aspiration biopsy (FNAB). Cytological diagnosis showed the presence of HC in 285 cases (2.6%), with a F/M ratio of 8.2/1. In 123 cases (43.2%) cytologic diagnosis resulted benign. A suspicious pattern of follicular neoplasm was observed in 159 cases (55.8%). Only in 3 cases (1%) thyroid carcinomas were preoperatively identified. No false positive or negative cases were observed. Among the HC lesions, 85 patients (29.8%) underwent thyroid surgery because of a malignant or suspicious cytologic diagnosis, continuous nodular growth despite LT4 therapy, mechanical compression or clinical judgement. The other two hundred patients were clinically evaluated and, one year later, repeated FNAB confirmed the cytologic diagnosis of benignity. Among the follicular neoplasm nodules, 80 cases (55.3%) were surgically explored, and thyroid carcinoma diagnosed in 30 of them (37.5%), this percentage being greater than that observed in the group of non-HC follicular neoplasm (17%). Pathologic criteria for malignancy (vascular invasion, transcapsular penetration, destructive capsular invasion) were described in 25 out of all carcinomas.

High plasma levels of endothelin-1 in untreated Addison's disease

The aim of this study has been to investigate the plasma endothelin-1 (ET-1) levels in adult patients with proven Addison's disease (AD). Plasma ET-1 levels were measured in 29 subjects (17 males and 12 females, aged between 20 and 54 years): 15 of them were patients with AD and 14 were sex- and age-matched normal subjects, used as a control group. All patients with AD have been studied under basal conditions and nine of them also after 2 weeks on oral corticosteroid therapy (individual cortisol dosage ranging from 25 to 37.5 mg/day and 0.1 mg/day 9 alpha-fluorohydrocortisone). Extracted plasma ET-1 was determined by a specific radioimmunoassay using rabbit endothelin antisera. Mean ET-1 values in the patients with AD were three times higher than in normal subjects (21.09 +/- 4.38 pg/ml vs 6.72 +/- 1.74 pg/ml; p < 0.0001). Plasma ET-1 levels assayed in the patients with AD after 2 weeks of corticosteroid therapy were significantly decreased (14.47 +/- 3.7 pg/ml vs 22.8 +/- 5.2 pg/ml; -37%; p < 0.001) compared to values in untreated patients. However, the plasma ET-1 values obtained following corticosteroid therapy were still significantly higher (p < 0.001) than those detected in the control subjects. These results clearly indicate that patients with untreated AD have increased circulating ET-1 levels that may be reduced by short-term corticosteroid therapy.

Increased plasma levels of endothelin-1 in patients with hyperthyroidism

Plasma concentrations of endothelin-1 (ET-1) were measured in 25 hyperthyroid subjects, 15 hypothyroid subjects, and 21 age-matched normal controls. In hyperthyroid patients, plasma concentrations of ET-1 were significantly higher than in the control group (P < .0001) and in hypothyroid patients (P < .0001). In contrast, no differences were found between hypothyroid patients and controls. Plasma levels of ET-1 were similarly elevated as in patients with Graves' disease and those with toxic adenoma. No correlations were found between plasma ET-1 levels, thyroid hormones, and thyrotropin (TSH) in hyperthyroid, hypothyroid, and euthyroid groups. The results of our study clearly indicate that in hyperthyroidism, circulating levels of ET-1 are strongly increased, although the pathogenesis of the increase is unclear.

Thyroid homeostasis and retinol circulating complex relationships in a severe iodine-deficient area of Senegal

In adult subjects living in a severely iodine-deficient area (median urinary iodine 10 microgram/L), we evaluated the biochemical parameters of protein malnutrition in relation to thyroid homeostasis. Serum transthyretine (TTR), retinol binding protein (RBP) and retinol, all components of the retinol circulating complex (RCC), as well as ceruloplasmin levels, were determined in 63 subjects (44 F/19 M). These comprised 21 controls, 31 who were euthyroid with goiter WHO stage 2 or 3 and 11 who met the criteria of hypothyroidism (i.e. FT4 < 8 pmol/L and TSH > 4.13 mU/L) with goiter stage no more than 1b. No differences in the values of TTR and RBP were found between males and females, whereas the retinol values were slightly higher in males. The mean retinol binding protein values were lower than the normal range in all three groups but were significantly lower (p < 0.01; < 0.05) in hypothyroid subjects than in the other two groups. All hypothyroid subjects exhibited reduced retinol binding protein levels and 1/3 of them showed a marked decrease. The circulating levels of transthyretine were also lower than the normal range for western countries. 45% of the hypothyroid, 26% of goitrous and 9% of control subjects exhibited a transthyretine lower than 12 mg/dl, but the mean values were not dissimilar. The mean retinol values were within the normal range in all three groups but were lower in hypothyroid as compared to the controls (< 0.01). The resulting retinol/RBP ratio was over 1 in both the whole sample and in the subgroups. Ceruloplasmin levels were in the normal range in all groups. The data indicated that hypothyroid subjects had reduced retinol binding protein and retinol circulating complex network compared to euthyroid subjects.

Reduced serum angiotensin converting enzyme activity in children with congenital hypothyroidism

In this study levels of serum angiotensin converting enzyme (SACE) were evaluated using colorimetric method in 24 children with congenital hypothyroidism, 28 children from an iodine deficient zone (14 euthyroid, 14 subclinically hypothyroid) and 21 normal children. In the children with congenital hypothyroidism SACE levels (28.15 +/- 6.67 nmol/ml/min) were significantly lower (p < 0.05) than SACE levels in normal children (33.87 +/- 7.00 nmol/ml/min) and in children from an iodine deficient zone (subclinical hypothyroid: 36.05 +/- 7.88 nmol/ml/min or euthyroid: 39.61 +/- 6.83 nmol/ml/min). No statistical difference in SACE levels was revealed in either normal subjects or children from an iodine deficient zone. SACE levels among all the groups were not shown to be different in relation to sex. Average TSH levels, as expected, were significantly higher (p < 0.05) in children with congenital hypothyroidism. The correlation between SACE and TSH levels did not demonstrate a statistical significance in any of the groups studied. In conclusion, our data demonstrated that levels of SACE were significantly reduced in children with congenital hypothyroidism.

Ischemia in collateral-dependent myocardium: effects of nifedipine and diltiazem in man

It has recently been shown that ischemia in collateral-dependent myocardium may develop at a very variable threshold in anginal patients; accordingly, the aim of this study was to assess whether nifedipine and diltiazem can increase blood flow to collateralized myocardium in man. Nine patients with complete coronary occlusion filled by collaterals, with no other coronary stenosis, normal left ventricular function, and reproducibly positive exercise tests were studied. They underwent exercise tests off therapy and after acute randomized administration of nifedipine (10 mg sublingually), diltiazem (120 mg orally), and nitroglycerin (0.5 mg sublingually), the latter a drug known to increase blood flow to collateralized myocardium. Following nifedipine, time to 1 mm ST segment depression increased significantly (from 430 +/- 176 to 576 +/- 205 seconds, p < 0.01), while heart rate and rate-pressure product remained unchanged (115 +/- 16 vs 121 +/- 17 beats/min and 199 +/- 29 vs 204 +/- 44 beats/min.mm Hg.10(2), respectively, p = NS for both). Similarly, diltiazem significantly increased time to ischemic threshold from baseline to 638 +/- 125 seconds (p < 0.01), but did not change heart rate and rate-pressure product at 1 mm ST segment depression. Submaximal rate-pressure products were significantly lowered by both nifedipine and diltiazem. Nitroglycerin not only significantly improved time to ischemic threshold (from baseline to 666 +/- 76 seconds, p < 0.01), but also increased heart rate (from baseline to 137 +/- 16 beats/min, p < 0.01) and rate-pressure product (from baseline to 242 +/- 48 beats/min.mm Hg.10(2), p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

[Long-term treatment of stable angina pectoris with gallopamil]

BACKGROUND

The effects of long-term treatment with gallopamil 50 mg t.i.d were assessed in 8 patients, 7 males and 1 female, aged 47-69 years, with stable angina pectoris, positive exercise tests, coronary artery disease and no previous myocardial infarction.

METHODS

Clinical and ECG parameters as well as exercise testing, 24-hour Holter and echocardiography were assessed before treatment, after 3 months, after 1 and 2 years of treatment, and following final wash-out.

RESULTS

Comparing each treatment period to baseline, a significant decrease in resting heart rate (from 66 +/- 9 beats/min at baseline to 56 +/- 7 beats/min after 3 months [p < 0.01], 59 +/- 8 beats/min after 1 year [p < 0.05] and 58 +/- 9 beats/min after 2 years [p < 0.05]), systolic (from 162 +/- 19 mmHg at baseline to 147 +/- 12 mmHg after 3 months [p < 0.05], 146 +/- 20 mmHg after 1 year [p < 0.01] and 146 +/- 27 mmHg after 2 years [p < 0.05]), and diastolic (from 89 +/- 6 mmHg to 82 +/- 7 after 3 months [p < 0.05], 82 +/- 4 after 1 year [p < 0.05] and 83 +/- 4 after 2 years [p < 0.05]) blood pressure was observed. Exercise time significantly improved (from 596 +/- 209 seconds to 802 +/- 66 seconds after 3 months [p < 0.01], 710 +/- 167 seconds after 1 year [p < 0.05] and 723 +/- 125 seconds after 2 year [p < 0.05]), while heart rate and rate-pressure product at peak exercise did not change. The number of ischemic episodes and the total ischemic time per 24 hours significantly decreased (from 35 +/- 15 min to 12 +/- 10 min after 3 months [p < 0.05], 10 +/- 8 min after 1 year [p < 0.05] and 11 +/- 9 min after 2 years [p < 0.05]). Ejection fraction increased (from 66 +/- 10% to 77 +/- 7% after 3 months [p < 0.01], 80 +/- 5% after 1 year [p < 0.01] and 80 +/- 3% after 2 years [p < 0.01]), while contractility, as expressed by the end-systolic stress/end systolic volume ratio remained unchanged. No serious side-effects or biochemical abnormalities developed.

CONCLUSIONS

Gallopamil appears to be safe, well tolerated and effective in the long term control of angina pectoris; its effects are fully developed at 3 months and persist unchanged after 2 years. For its hypotensive action and the lack of significant effects on myocardial contractility, gallopamil appears to be potentially useful in patients with associated angina and hypertension and in patients with impaired left ventricular function.

Pattern of thyroid hormones in mildly protein-deficient women in area endemic for goiter

This study refers to 23 nonpregnant and 5 pregnant Ethiopian women living in a severely iodine-deficient area exposed to marginal chronic protein malnutrition. About half the study group exhibited goiter. The components of retinol circulating complex have been measured: transthyretin, retinol, and retinol-binding protein were 31 +/- 8 mg/dl, 36 +/- 6 micrograms/dl, and 3.1 +/- 0.6 mg/dl, respectively. No differences in circulating thyroid hormone pattern were found among goitrous and nongoitrous subjects. In nonpregnant women, the circulating thyroid hormone pattern was characterized by a low total T4 (TT4, 53 ng/ml), whereas free T4 (FT4, 0.5 ng/dl) was below the lower level of the range. Thyroid-stimulating hormone and FT3 were in the normal range, and TT3 was at the upper level of the range. The pregnant women exhibited the expected increase in total thyroid hormones (TT3 3.0 ng/ml, TT4 96 ng/ml), whereas the free fractions were equal to those of the nonpregnant subjects (FT3 2.5 pg/ml, FT4 0.6 ng/dl). In the whole group, the T3-T4 ratio was 3.4 x 10(-2), i.e., twice the normal ratio. No antibodies against thyroid structures were detected. These results indicate that the circulating thyroid hormone pattern of these marginally malnourished women differs from that reported for subjects with pure protein-calorie malnutrition or exposed to chronic iodine deficiency only. The main difference is that, even in the presence of low TT4 and FT4, the hypophysis-thyroid axis has apparently remained unchanged. The normal levels of TT3 and FT3, may account for the normal thyroid-hypophysis feedback.

Effect of extracellular sodium on thyroid hormone uptake by mouse thymocytes

In mouse thymocytes, a stereospecific saturable energy-dependent and ouabain-inhibitable system facilitates T3, but not T4, entry. We studied here the effect of sodium depletion on cellular uptake of thyroid hormones by mouse thymocytes. Time-course experiments indicated that extracellular sodium depletion reduced [125I]T3 uptake at each time studied. At equilibrium, the removal of extracellular sodium and its substitution with isoosmotic choline decreased saturable [125I]T3 uptake by 60 +/- 10%; this effect was dose dependent. The substitution of sodium with lithium, instead of choline, had no effect on the uptake process. [125I]T4 uptake was lower than that of [125I]T3 and not affected by sodium depletion. The half-maximal effect of sodium deprivation on [125I]T3 uptake was reached at an extracellular sodium concentration of about 40 mM. The variation of external pH influenced T3 accumulation by thymocytes. [125I]T3 progressively decreased from acid to alkaline pH under normal and sodium-depleted conditions; however, the sodium-dependent fraction was more than doubled at physiological pH compared to that at more acidic and more alkaline pH. The sodium ionophore monensin decreased T3 uptake by 51% at a concentration of 20 microM. These results indicated the existence of a sodium-related mechanism of T3 uptake into mouse thymocytes that does not operate for T4 uptake.

[Hypothyroidism: current clinical, physiopathological and therapeutic aspects]

The correct diagnosis and an appropriate classification of hypothyroidism must be considered on the light of the most recent physiopathological and molecular information. Hypothyroidism is no longer regarded as the rare disease characterized by a myxedematous condition as described since one century ago. With the present improvement of the diagnostic tools the thyroid hypofunction now includes all those blunted forms that are classified as subclinical or latent hypothyroidism. Thus, the hypothyroid syndrome, previously considered a rare event in its overt form, reaches a prevalence of 14% in female aged over fifty years. Following a coherent, concise historical review, the influence of age, surgery, drugs and autoimmunity on the etiology of the disease are critically discussed. The early detection and treatment of congenital hypothyroidism, to avoid an irreversible damage of the central nervous system, by means of the screening on the paper spot is also stressed. Replacement therapy with synthetic levothyroxine has to be personalized, according to the age and other clinical conditions, and should be prescribed also in the treatment of subclinical hypothyroidism.

Carrier-mediated [125I]-T3 uptake by mouse thymocytes

Thyroid hormone entry into the thymocyte, a thyroid hormone target, was investigated by incubating the cells with tracer amounts of [125I]L-T3. At 37 C T3 uptake was linear with time up to 2 min, and then approached a plateau. The specific T3 uptake, obtained by subtracting the uptake in the presence of excess unlabeled T3, represented 48 +/- 6% of the total at equilibrium. Unlabeled L-T4, D-T3, and triiodothyroacetic acid were less effective than L-T3 in reducing [125I]T3 uptake. Kinetic studies on the initial rate of T3 uptake indicated, for the saturable process, a maximum velocity of approximately 1 pmol/10(6) cells.min and a Km of approximately 0.8 nM. Lowering incubation temperature to 4 C resulted in a two thirds reduction of the total T3 uptake. Washout experiments indicated a different hormone release, being more rapid for cells incubated at 4 C than at 37 C; at 30 min 70% of labeled T3 was released when incubation was carried out at 4 C compared to only 35% after incubation at 37 C, indicating the major intracellular location of the hormone at the latter temperature. An energy requirement of T3 uptake in thymocytes was shown by sensitivity to oligomycin; the effect was dose dependent, showing a maximal decrease in specific uptake of 85%. The involvement of cation movement in the entry process of T3 was indicated by the sensitivity to ouabain. These results indicate the existence of a stereospecific, energy-dependent, saturable process for T3 entry in thymocytes.

Insulin effect on thyroid hormone uptake in rat skeletal muscle

Previous work has indicated that thyroid hormone entry into cells includes an energy-dependent, saturable process. In this study we investigated the effect of insulin on T3 uptake in rat skeletal muscle. Intact soleus muscles were preincubated for 30 minuted at 37 degrees C, pH 7.4, in modified Krebs-Ringer bicarbonate buffer in the presence or absence of insulin and then for 60 minutes after adding 50 pmol/L [125I] T3. The results showed a stimulatory effect of insulin that was half maximal at 33 nmol/L and maximal at 100 nmol/L. Addition of 10 mumol/L T3 to the incubation medium completely blocked the effect, showing that the action of insulin is exerted only on the specific component of T3 uptake. The substitution of extracellular sodium with an equimolar amount of lithium also prevented the insulin effect. [125I] T4 uptake was unaffected by insulin. These results indicate that T3 uptake in skeletal muscle is sensitive to insulin, that insulin stimulates the specific component of T3 uptake in a dose-dependent manner, and that its action requires extracellular sodium. In contrast, T4 uptake is insensitive to insulin action in accordance with previous results that indicated passive diffusion as its major pathway for cell entry.

Role of sodium in thyroid hormone uptake by rat skeletal muscle

Whether Na+ movement through the plasma membrane plays a role in thyroid hormone uptake was investigated in intact rat soleus muscles. After preincubation for 120 min at 37 degrees C in modified Krebs-Ringer bicarbonate containing 140 or 5 mM Na+ plus choline or lithium to maintain osmolarity, muscles were incubated with 50 pM [125I]triiodo-L-thyronine (T3) or [125I]L-thyroxine (T4) for 60 min. T3 uptake was decreased when extracellular Na+ was replaced by either choline or lithium, the amount of decrease corresponding to the specific (or saturable) uptake component. Monensin, an ionophore that stimulates Na+ entry, increased T3 uptake at 140 mM Na+ but not at 5 mM Na+. Amiloride, a Na+/H+ exchange inhibitor, had no effect on T3 uptake under basal conditions or when Na+ was replaced by choline, but reversed the action of lithium. Ouabain, an inhibitor of Na+/K+ ATPase, reduced specific T3 uptake. T4 uptake was unaffected by low extracellular Na+. These results are consistent with a major role of Na+ movement in T3 uptake by skeletal muscle, but not in T4 uptake, and suggest an involvement of membrane pumps in this process.