Amiodarone-induced thyrotoxicosis associated with thyrotropin receptor antibody

Since amiodarone was first marketed in 1992 in Japan, the incidence of amiodarone-induced thyrotoxicosis (AIT) has been increasing. Among 12 thyrotoxic patients, a patient with arrhythmogenic right ventricular dysplasia, who had been taking amiodarone for 4 years, developed thyrotoxicosis with subacute onset, accompanied by transiently positive thyrotropin (TSH) receptor antibody (TRAb), or thyrotropin-binding inhibiting immunoglobulin (TBII). The immunoglobulin G (IgG) obtained from the TRAb-positive serum of the patient elicited no thyroid hormone-releasing activity in cultured human thyroid follicles, whereas all IgGs obtained from untreated Graves' disease elicited positive results. These in vitro findings and clinical course suggest that TRAb/TBII without thyroid-stimulating activity may develop in patients with amiodarone-induced destructive thyroiditis, as reported in patients with destructive thyroiditis, such as subacute and silent thyroiditis.

Hypercalcemia in an euthyroid patient with secondary hypoadrenalism and diabetes insipidus due to hypothalamic tumor

A 20-year-old Japanese man with a hypothalamic tumor (most likely germ-cell tumor) which caused secondary hypoadrenalism, hypogonadism and diabetes insipidus developed hypercalcemia and acute renal failure. The serum levels of intact PTH (iPTH), PTH-related protein (PTH-rP), 1,25-dihydroxy vitamin D (1,25- (OH)2 D), ACTH, cortisol, gonadotropins and testosterone were decreased, but his serum levels of triiodothyronine (T3) and thyroxine (T4) were within the normal range at admission, with depressed TSH and slightly increased thyroglobulin. The hypercalcemia was refractory to extensive hydration and calcitonin, but was ameliorated by pamidronate. After irradiation of the hypothalamic tumor, panhypopituitarism gradually developed. The patient has been normocalcemic for the last 2 years and is doing well under replacement therapy with glucocorticoid, L-thyroxine, methyltestosterone and 1-desamino D arginine vasopressin (dDAVP). As to the mechanism of euthyroidism at admission, transient destructive thyroiditis associated with hypopituitarism or delayed development of hypothyroidism following the hypoadrenalism was suggested. This is the first reported case of hypercalcemia in secondary hypoadrenalism due to hypothalamic tumor. Hypercalcemia was most likely induced by increased bone resorption, which was probably elicited by the combined effects of deficient glucocorticoid and sufficient thyroid hormones in addition to hypovolemia and reduced renal calcium excretion. Furthermore, severe dehydration due to diabetes insipidus and disturbance of thirst sensation caused by the hypothalamic tumor aggravated the hypercalcemia, leading to acute renal failure.

Deferential roles of angiotensin receptor subtypes in adrenocortical function in mice

The functional significance of angiotensin II (Ang II) receptor subtypes in adrenals remains unknown. Ang II receptor type 1a (AT1a) expression was localized by in situ hybridization to the zona glomerulosa and zona fasciculata, while AT1b was localized to the zona glomerulosa. Plasma aldosterone and corticosterone levels were measured after injection with Ang II or the type 2 receptor (AT2) agonist CGP-42112 in wild-type and AT1a deficient mice. Aldosterone and corticosterone levels were lower in AT1a deficient mice. Ang II increased plasma aldosterone levels in AT1a deficient mice, but to a lesser extent in mice pretreated with nonselective AT1a/AT1b antagonist, CV-11974. CGP-42112 did not affect aldosterone levels. Ang II increased corticosterone levels in wild-type mice but not in AT1a deficient mice. Results suggest Ang II stimulates aldosterone secretion via AT1a and AT1b in the zona glomerulosa and corticosterone secretion via AT1a in the zona fasciculata, and provide first evidence for differential roles of AT1a and AT1b in the adrenals.

The relatively high frequency of p53 gene mutations in multiple and malignant phaeochromocytomas

To explore the clinical significance of p53 in the pathogenesis of adrenal neoplasms, we investigated the incidence of p53 gene mutations in functioning human adrenal tumours using the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) technique to screen p53 exons 4 to 9. We examined 29 adrenocortical adenomas (primary aldosteronism, n=17; Cushing's syndrome, n=12, all benign), and 33 phaeochromocytomas (benign solitary, n=18; benign multiple, n=5; malignant, n=10) in Japanese and Chinese patients. PCR-SSCP did not show any abnormal band-shifts in any of the adrenocortical adenoma and benign solitary phaeochromocytoma tissues. In contrast, six phaeochromocytoma tissues (two cases benign multiple, four cases malignant) showed PCR-SSCP band-shifts. Subsequent DNA sequencing analysis of the shifted bands revealed six cases with nine mutations or intronic sequence alterations: three cases contained sequence alterations within intronic regions, three cases with silent mutation (sequence alteration in codon without amino acid alteration), and three cases contained missense mutations (one case each in exons 5, 6 and 9). Immunohistochemical staining demonstrated that two of three cases with missense mutations and one case with an intronic sequence alteration over-expressed p53 protein in tumour cell nuclei. We observed no association between p53 gene mutation and p21/WAF1/Cip-1 expression. The relatively high incidence of p53 gene mutations or intronic sequence alteration in multiple and malignant phaeochromocytomas, but not in benign solitary cases, suggests that p53 mutation could play some role in the pathogenesis of multiple and/or malignant phaeochromocytomas.

Angiotensin II stimulates both aldosterone secretion and DNA synthesis via type 1 but not type 2 receptors in bovine adrenocortical cells

Angiotensin II (Ang II) type 2 receptor (AT2) has been shown to counteract the type 1 receptor (AT1)-mediated biological actions of Ang II in the cardiovascular system. The biological significance of AT2 receptor in the adrenals however remains unknown. In the present study, we investigated the roles of AT1 and AT2 receptor subtypes in the regulation of aldosterone secretion and DNA synthesis in bovine adrenocortical zona glomerulosa cells in vitro. Ang II (1 mumol/l)-stimulated aldosterone secretion was completely suppressed by AT1 antagonist CV-11974 but not affected by AT2 receptor antagonist PD-123319. Effects on DNA synthesis were investigated by determining the incorporation of BrdU into the nuclei of the cultured zona glomerulosa cells. Ang II (1 mumol/l)-stimulated DNA synthesis of the cells was also completely suppressed by CV-11974 but not by PD-123319. These results suggest that AT1 receptor but not AT2 receptor is the predominant receptor subtype which mediates the Ang II-stimulated aldosterone secretion and cell growth in bovine adrenocortical cells.

Cardiac malignant pheochromocytoma with bone metastases

A patient with malignant cardiac pheochromocytoma with bone metastases is described. The primary tumor was located between the pulmonary trunk and the left atrium, while metastatic lesions were found in the iliac bones. Treatments with antihypertensive agents, alpha-methylparatyrosine, and combination chemotherapy with cyclophosphamide, vincristine, and dacarbazine partially improved the patient's symptoms, catecholamine levels, and the metastatic lesion of the iliac bones. However, the primary tumor in the heart progressively increased in size and the patient died of disseminated intravascular coagulation and other various complications about 4 years after the diagnosis of the disease.

Effect of growth hormone (GH) on serum concentrations of leptin: study in patients with acromegaly and GH deficiency

As leptin, an ob gene product, plays a pivotal role in the regulation of adiposity and energy homeostasis, the level of its expression is likely to fluctuate under various physiological, nutritional, and disease conditions. Reports regarding the effect of GH on serum leptin levels are inconsistent. We have measured serum leptin levels and correlated them with several variables in patients with acromegaly, patients with adult GH deficiency (GHD), and normal controls. In 116 normal subjects, the mean serum concentration of leptin was 5.0+/-2.8 (mean +/- SD) ng/mL in men (n = 42) and 10.7+/-7.3 ng/mL in women (n = 73), respectively. As reported previously, the leptin levels in women were significantly (P < 0.001) higher than in men, and there was a strong positive correlation between log-transformed serum leptin levels and percent body fat in simple regression analysis (in men: r = 0.606; P < 0.0001; in women: r = 0.707; P < 0.0001). In 36 acromegalic patients, the percent body fat mass was significantly lower than that in normal subjects, and the mean serum leptin level was 2.2+/-1.8 ng/mL in men (n = 18) and 3.6+/-2.5 ng/mL in women (n = 18). Analysis of covariance revealed that serum leptin levels in acromegalics were significantly lower than those in normal subjects after correcting percent body fat (P = 0.016 for men and P < 0001 for women). In male patients with GHD (n = 20), the mean percent body fat was significantly (P < 0.05) higher than that in age-matched controls, whereas the value in female GHD patients (n = 15) did not differ from that in age-matched controls. Serum leptin levels in GHD patients were 5.1+/-2.5 ng/mL in men and 11.5+/-8.1 ng/mL in women, which were not different from those in normal subjects adjusted for percent body fat mass. In multiple regression analysis models with log-transformed leptin as the dependent variable, gender, percent body fat (or body fat mass), and serum insulin-like growth factor I levels entered the equations at a statistically significant level. These data suggest that excess GH/insulin-like growth factor I reduces serum leptin levels by reducing body fat mass and/or by unknown mechanisms.

The genomic organization of the human corticotropin-releasing factor type-1 receptor

We determined the genomic organization of human CRF type-1 receptor (hCRF-R1). The gene coding for hCRF-R1 consists of at least 14 exons and spans over 20 kilobases. hCRF-R1's three reported isoforms originate from the same gene by alternative splicing. The first hCRF-R1, which binds to CRF with the highest affinity and transduces the most sensitive cAMP accumulation in response to CRF, is encoded in a total of 13 exons, the only one excluded being exon 6. The second isoform contains an additional 29-amino acid sequence which corresponds to exon 6. Unlike the first isoform, the third lacks a 40-amino acid sequence, corresponding to exon 3. Exon-intron boundaries are the same as that of the consensus sequence. Locations of introns in the coding sequence are similar to human CRF-R1, rat CRF-R1, human CRF-R2alpha and others belonging to the human glucagon receptor family.

The importance of body weight history in the occurrence and recovery of osteoporosis in patients with anorexia nervosa: evaluation by dual X-ray absorptiometry and bone metabolic markers

In order to investigate the risk factors, pathogenesis and natural course of the osteoporosis frequently seen in anorexia nervosa, we measured the bone mineral density (BMD) of the lumbar spine using dual X-ray absorptiometry in 51 Japanese female patients with anorexia nervosa, and followed the change in BMD of 29 patients for 11 to 46 months. We also evaluated the serum osteocalcin and the urinary CrossLaps, degradation products of collagen I, in 103 samples obtained from 51 patients. There was a significant correlation between the spinal BMD and the duration of emaciation below a body mass index (BMI) of 15kg/m2 (r= -0.652, P<0.0001) and 16kg/m2 (r= -0.647, P<0.0001). The increase in BMD per year in the 29 patients significantly correlated with the BMI at the time of entry of each follow-up period (r= 0. 712, P<0.0001). The critical BMI for a positive increase in BMD was 16.4+/-0.3 kg/m2 (mean+/-S.E.M.). The serum osteocalcin declined, while the urinary CrossLaps increased in proportion to a decrease in BMI. Both markers were normalized in patients whose BMI was between 16.4 and 18.5 kg/m2. The ratio of urinary CrossLaps to serum osteocalcin correlated with BMI (r= -0.664, P<0.0001). We conclude that the body weight history is the most important predictor of the presence of osteoporosis as well as of recovery The BMD of patients does not increase to the normal range even several years after the recovery from this disorder, and they remain a high-risk group for osteoporosis in the future.

Age-dependent decline in cortisol levels and clinical manifestations in patients with ACTH-independent Cushing's syndrome

OBJECTIVE

Adrenocortical cells change with age in both subcellular morphology and level of steroidogenesis. This study evaluates the influence of aging on hypercortisolism and clinical manifestations in patients with ACTH-independent Cushing's syndrome due to a cortisol-secreting adrenal adenoma (CS).

DESIGN

Restrospective study.

PATIENTS

Thirty-six (33 females and 3 males) with CS. 31 healthy controls were age- and sex-matched to CS patients.

MEASUREMENT

Patient age at diagnosis was compared to the degree of hypercortisolism and clinical manifestations. The degree of hypercortisolism was estimated using serum cortisol levels and urinary free cortisol excretion. Positive clinical manifestations were quantified using 12 symptoms and signs which resulted in a clinical score for each patient. Endogenous creatinine clearance, estimated disease duration and gender were analysed as possible factors affecting adenoma-secreated cortisol.

RESULTS

Patient age correlated negatively with serum cortisol level (r = -0.417, P = 0.0107, n = 36) and urinary excretion of free cortisol (r = -0.613, P = 0.0002, n = 31). Analysis of Spearman's rank correlation showed that the clinical score decreased with age (rho = -0.631, P = 0.0004, n = 33). Oedema, weakness/myopathy, hirsutism, striae and psychological changes were infrequent symptoms in the elderly. Using stepwise multiple regression analysis, we estimated the clinical score (Y) by factors of serum cortisol levels (X1:nmol/l), age (X2: years of age) and gender (X3: gender; female = 1, male = 0), i.e. Y = 4.771 + 0.004 X1 - 0.064 X2 + 2.548 X3 (r = 0.743, P < 0.0001, n = 33). Results suggested that aging both suppressed cortisol secretion and repressed manifestations directly as an independent factor, although its direct effect may be weak.

CONCLUSIONS

Our findings indicated the importance of age as a factor modulating hormonal levels and possible clinical manifestations in patients with cortisol-secreting adenomas.

Stress-induced changes of gene expression in the paraventricular nucleus are enhanced in spontaneously hypertensive rats

Heightened hypothalamic-pituitary-adrenal (HPA) axis responses have been implicated in hypertension in the spontaneously hypertensive rat (SHR), but the exact mechanisms involved are poorly understood. To determine changes in gene expression in SHR in the paraventricular nucleus (PVN), stress-induced accumulation of CRF, CRF type 1 receptor (CRFR-1) genes, and immediate-early genes were examined using in situ hybridization in young (5 weeks old) and adult (12 weeks old) stroke-prone SHR (SHRSP), compared with normotensive Wistar Kyoto (WKY) rats. Restraint stress-induced accumulation of c-fos, jun B, and NGFI-B mRNA, and CRF hnRNA in the PVN was significantly higher in young and adult SHRSP than in WKY rats at 30 min, except for c-fos in young rats. CRFR-1 mRNA expression in the PVN was also significantly higher in adult SHRSP than in WKY rats at 120 min after stress onset. CRF mRNA was increased in response to stress in young SHRSP. The basal CRF mRNA level in the PVN was significantly lower in adult SHRSP than in WKY rats. Young SHRSP exhibit greater ACTH responses to stress without significant changes in plasma corticosterone concentrations. The adult SHRSP exhibited lower baseline concentrations of corticosterone and similar corticosterone response to stress with enhanced secretion of ACTH. Overall, these results demonstrated that stress-induced activation of immediate early genes and CRF gene transcription in the PVN, and ACTH secretion is enhanced in early hypertensive, young, and adult SHRSP, suggesting that they are probably not the result of chronic alterations in blood pressure. The abnormal hypothalamic-pituitary response to stress thus appears to be related to the development of hypertension.

Establishment of a stable HL60 subline having the potential for monocytic differentiation using granulocyte-macrophage colony-stimulating factor: possible use for the study of monocytic differentiation and oxidative stress

A stable HL60 subline having the potential for monocytic differentiation was established by use of GM-CSF. HL60, a human promyelocytic cell line, has frequently been employed for research in the fields of monocytic differentiation and atherosclerosis because of its potential to differentiate into either granulocytes or monocytes. However, HL60 are frequently seen to change their phenotype during long-term culture. To date, many sublines or variants of HL60 cells have been established. However, most of them display diminished or complete loss of activities that characterize parental cells. The present study was conducted to establish a stable HL60 subline with the potential for monocytic differentiation. Firstly, a single HL60 cell was isolated by limiting dilution, and was successfully proliferated by incubation with GM-CSF. Secondly, from this population, cells were selected that had the ability to generate superoxide after VD-induced monocytic differentiation. Cells obtained in this manner (designated HL60/DU-1) exhibited expression of CD14 and CD11b and suppression of CD3 expression after monocytic differentiation. NBT positivity showed a consistent level of over 971% after a 6-day challenge with VD throughout the experimental period of 12 months. HL60/DU-1 cells, which were cryopreserved in liquid nitrogen for 6 months, thawed and re-cultured, exhibited over 97% NBT positivity. Carvedilol and probucol, which exhibit antioxidative activity, inhibited superoxide release from the differentiated HL60/DU-1 cells. HL60/DU-1 cell line is a promising model for the study of monocytic differentiation and the effects of oxygen radicals.

Serum high molecular weight form of insulin-like growth factor II from patients with non-islet cell tumor hypoglycemia is O-glycosylated

Non-islet cell tumor hypoglycemia (NICTH) is one of major causes of fasting hypoglycemia. In some patients with NICTH, insulin-like growth factor II (IGF-II) produced by and secreted from the tumors is thought to be a hypoglycemic agent. In patients with NICTH, the major form of IGF-II is high molecular weight form of IGF-II, designated as big IGF-II. The generation of big IGF-II in the NICTH syndrome is unclear. It has been reported that in the patients with NICTH big IGF-II lacks normal E-domain O-linked glycosylation, suggesting that the patient's big IGF-II might be generated by abnormal processing of pro-IGF-II. However, we have found that the apparent size of big IGF-II varies in sera from the patients with NICTH, and that there is a possibility that slower migration pattern of IGF-II might be because of a different size of sugar moiety attached to pro-IGF-II. In the present study using the sera from 10 patients with NICTH, we investigated the effect of O-glycosidase digestion on migration of IGF-II and analyzed the results by Western immunoblot. By Western immunoblot analysis the big IGF-II was reduced in size to 9.5 kDa in the enzyme-treated sera of the 10 patients with NICTH. The migration pattern is similar to that observed in sera of normal subjects after O-glycosidase digestion. These data indicate that big IGF-II from patients with NICTH is O-glycosylated, and the sizes of the sugar moiety are larger than those from normal subjects suggesting abnormal glycosylation in NICTH.

Gene expression and roles of angiotensin II type 1 and type 2 receptors in human adrenals

Although stimulation of aldosterone secretion is one of the functions of angiotensin II, the gene expression and biological significance of the angiotensin II receptor subtypes, AT1 and AT2, in the human adrenal have not been characterized. We therefore investigated the transcription levels of the receptor subtype genes and their roles in regulation of steroid secretion by human adrenals. The expression of AT1 and AT2 receptor mRNA was assessed by reverse transcription-polymerase chain reaction followed by Southern blot analysis in normal adrenocortical tissues (n = 6) and a series of adrenal tumour tissues: aldosterone-producing adrenocortical adenoma (n=6), Cushing's syndrome (n = 6) and pheochromocytoma (n = 6). The role of the two receptor subtypes in steroid secretion in vitro was examined by incubating the tissue with angiotensin II(1 microM) with or without the selective AT1 antagonist CV-11974 (1 microM). Both AT1 and AT2 receptor mRNA transcripts were demonstrated in all of the human adrenal tissues tested. Angiotensin II-induced aldosterone secretion was suppressed 50% upon the addition of CV-11974. The selective AT2 agonist CGP-42112 increased aldosterone secretion by 55% over the control, which was not suppressed by CV-11974. Angiotensin II and CGP-42112 did not affect cortisol secretion. These results suggest that both AT2 and AT1 receptors may be involved in the regulation of aldosterone secretion and tumorigenesis of the human adrenals.

Beta-adrenoceptor antagonist propranolol potentiates hypotensive action of natriuretic peptides

Beta-adrenoceptor antagonists are known to increase plasma atrial natriuretic peptide (ANP) levels despite their hypotensive action. The aim of the present study was to examine the role of the ANP system in the antihypertensive effects of a beta-adrenoceptor antagonist. We investigated the effects of propranolol (75 mg kg(-1) day(-1), p.o., 4 weeks) on the ANP system in stroke-prone spontaneously hypertensive rats. Plasma ANP levels were significantly higher in the propranolol group than in the control group. Both receptor densities and mRNA levels of ANP(C) receptor were significantly decreased in the lung as the major site of ANP clearance from the circulation. In contrast, both central venous pressure and ANP mRNA levels in the heart were not significantly different between the two groups. Under both basal and ANP-stimulated conditions, the cGMP content in the aorta was significantly greater in the propranolol group than in the control group, whereas the basal and stimulated cGMP content of the kidney was similar in the two groups. Inhibition of endogenous ANP action by a specific ANP receptor antagonist, HS-142-1, produced a greater increase of blood pressure in the propranolol group than in the control group. These results suggest potentiation of natriuretic peptide activity as a new antihypertensive mechanism of the beta-adrenoceptor antagonist propranolol.

Effects of tetramethylpyrazine, a Chinese medicine, on plasma endothelin-1 levels during acute pulmonary hypoxia in anesthetized dogs

Our study was designed to elucidate the effects of tetramethylpyrazine (TMP), a Chinese medicine, on plasma endothelin-1 (ET-1) levels in dogs with acute pulmonary alveolar hypoxia. Anesthetized dogs were used under artificial ventilation with room air or a hypoxic gas mixture (10% O2 and 90% N2) (n = 10) for 60 min. Effects of TMP (80 mg/kg) were studied by i.v. injection of TMP before exposure to hypoxia (n = 8). Mean pulmonary arterial pressure (PAPm), systemic arterial pressure (SAPm), right atrial pressure (RAP), pulmonary capillary wedge pressure (PCWP), cardiac output (CO), and heart rate (HR) were measured. The pulmonary vascular resistance (PVR) was calculated by the equation of (PAPm-PCWP) x 8/CO. Plasma ET-1 levels were determined in the abdominal aorta and pulmonary artery by RIA. The effects of TMP on PAP and plasma ET-1 level were evaluated by using percent increase in PAPm and the change of Da-pET (delta ET) before and after hypoxia. Both PAPm and PVR were significantly elevated 5 min after acute hypoxia over a period of 60 min, whereas CO and PCWP did not change. Plasma ET-1 levels in the abdominal aorta and Da-pET showed a significant increase. Administration of TMP significantly decreased the hypoxia-induced increase in the PAPm, PVR, and delta ET. These results suggest that TMP could be a useful therapeutic agent in the treatment of pulmonary hypertension induced by acute hypoxia through decrease of plasma ET-1 levels.

Immunoreactive endothelin levels in the vitreous fluid are decreased in diabetic patients with proliferative retinopathy

Endothelin (ET) plays an important role in the pathogenesis of various cardiovascular lesions. To elucidate the pathophysiologic significance of ET in the development of diabetic retinopathy, we determined immunoreactive ET levels in the vitreous fluid collected during vitrectomy in seven patients with non-insulin dependent diabetes mellitus with proliferative diabetic retinopathy and in 10 nondiabetic subjects as controls. Immunoreactive vitreous ET levels in diabetic patients with proliferative retinopathy (7.5 +/- 3.4 pg/ml, mean +/- SD) were significantly lower than those in the nondiabetic subjects (55.0 +/- 38.1 pg/ml; p < 0.005). The decreased rather than increased immunoreactive ET levels may simply reflect severe endothelial injury to the retinal vessels caused by diabetic microangiopathy rather than an important role in diabetic retinopathy.

Tetramethylpyrazine, a Chinese drug, blocks coronary vasoconstriction by endothelin-1 and decreases plasma endothelin-1 levels in experimental animals

The purpose of this study was to investigate effects of tetramethylpyrazine (TMP), a Chinese plant-derived medicine, on coronary vasoconstriction and related electrocardiographic and histologic changes caused by endothelin-1 (ET-1), and on plasma ET-1 levels. ET-1 (75 pmol) was administered into the left coronary artery (LCA) in anesthetized closed-chest dogs with and without prior infusion of TMP (80 mg/kg). Coronary arterial diameter (CAD) was determined by coronary arteriography (CAG). Blood pressure and electrocardiogram (ECG) were monitored continuously. Histologic damage in tissues was ascertained microscopically. Plasma ET-1 and 6-keto-PGF1 levels were determined by RIA 90 min after i.v. injection of TMP (25 mg/kg; n = 5) in rabbits. Intracoronary injection of ET-1 resulted in a significant vasoconstriction of the entire vascular bed of the LCA, with a decrease in CAD of 35.9 +/- 5.7% (n = 5; p < 0.01) and ischemic changes on ECG and in tissues of endocardium, myocardium, coronary endothelial cells, and capillary vessels. Pretreatment with TMP produced a significant increase in CAD by 38.5 +/- 7.8% (n = 5; p < 0.01) and greatly suppressed the vasoconstriction produced by ET-1. The myocardial tissue damage estimated from the ratio of ischemic area for the entire area after ET-1 injection (35.6%) was completely abolished by TMP (0.6%). In addition, TMP injection induced a significant decrease in plasma ET-1 levels and an increase in 6-keto-PGF1 levels in rabbits. The Chinese medicine TMP could be a useful therapeutic agent in ischemic heart disease by suppressing coronary vasoconstriction and ischemic changes in the tissues produced by ET-1.

Immunoreactive endothelin-1 and its receptors in human adrenal tissues

To elucidate the pathophysiologic significance of endothelin-1 (ET-1) in adrenal and the mechanism for reduced responsiveness to exogenous ET-1 in aldosterone-producing adenoma (APA), we have investigated ET-1 receptors by radioligand binding assay (RBA) in human normal adrenal (NA), APA, idiopathic hyperaldosteronism (IHA), and pheochromocytoma (PHEO), immunoreactive (ir-) ET-1 content in NA, APA and PHEO by radioimmunoassay (RIA), and immunohistochemical staining of ET-1 with the peroxidase-anti-peroxidase (PAP) method in NA, APA, and PHEO. A single class of high-affinity binding sites for ET-1 was found in human NA and tumor tissues. Dissociation constant (Kd) values of ET-1 receptors were similar in NA, APA, and IHA, but maximal binding capacity (Bmax) of ET-1 receptors was lower in APA than in NA and IHA. Both Kd and Bmax in PHEO were higher than those in NA, APA, and IHA. Ir-ET-1 content in tumors of APA and PHEO were higher than in NA. Immunohistochemical staining was more intense in the tumor cells of APA and PHEO than in NA. These results suggest that the reduced response to exogenous ET-1 in APA could be related to downregulation of ET-1 receptors in the tumor. Increased ET-1 content and receptors may lead to hypersecretion of catecholamine in PHEO. ET-1 produced in normal and tumor adrenal tissues may regulate aldosterone and catecholamine secretion from adrenals in a paracrine/autocrine fashion.

Gene expression of endothelin-1 and endothelial-type nitric oxide synthase in cardiovascular tissues of stroke-prone spontaneously hypertensive rats/Izm: effects of the angiotensin-converting enzyme inhibitor aracepril

We studied target organ-protective effects of aracepril, an angiotensin-converting enzyme inhibitor, and the expression of endothelin-1 (ET-1) and nitric oxide synthase (NOS) mRNA. Aracepril (30 mg/kg) was administered orally to Izumo strain of stroke-prone spontaneously hypertensive rats (SHR-SP/Izm) for 8 weeks from 4 weeks of age and for 4 weeks from 8 weeks of age. The expression of ET-1 and endothelial NOS (eNOS) mRNA in the heart, aorta, kidneys, and brain cortex, and the expression of neuronal NOS (bNOS) mRNA in brain cortex, were analyzed by RT-PCR/Southern blotting or RNase protection analysis. Administration of aracepril markedly lowered blood pressure and decreased left ventricular weight in SHR-SP/Izm. Expression of ET-1 mRNA in the heart, kidneys, and brain was significantly enhanced in SHR/SP/Izm compared with that in WKY/Izm. Aracepril significantly decreased the expression of ET-1 mRNA, whereas there was no significant change of that in the aorta. Although expression of eNOS mRNA in the heart, aorta, and kidneys did not show any significant difference between the two strains of rats, administration of aracepril for 8 weeks significantly decreased the expression of eNOS and bNOS mRNA in brain tissue. These results suggested that aracepril may protect major target organs by modifying the expression of ET-1 and NOS mRNA, in addition to its hypotensive effect.

Serum insulin-like growth factor II in 44 patients with non-islet cell tumor hypoglycemia

Serum insulin-like growth factor II (IGF-II) was characterized by radioimmunoassay and Western immunoblot in 44 patients with non-islet cell tumor hypoglycemia (NICTH). 31 of 44 patients with NICTH had big IGF-II in sera. When the presence of IGF-II in tumors from 20 patients was investigated, IGF-II in tumors was detected in 18 patients and these patients had big IGF-II in sera. In two patients whose tumors did not contain IGF-II, big IGF-II in sera was not detected. In six patients with IGF-II in tumors, hypoglycemia disappeared and the big IGF-II decreased after successful removal of the tumors. These data indicate that the big IGF-II could be related to hypoglycemia, and that the increased serum big IGF-II suggests IGF-II-producing NICTH. Serum IGF-II levels in 31 patients with big IGF-II were greater than those in 13 patients without it (Mean +/- SEM: 723+/-54 vs. 326+/-31 ng/ml), but the elevated IGF-II levels were found in only 13 patients. Serum IGF-I levels were low in all patients with NICTH. In the 13 patients without big IGF-II, serum IGF-II levels were lower than those in the patients with big IGF-II, and serum IGF-I levels were also low. Serum IGF-II/IGF-I ratios in the patients with big IGF-II were elevated and greater than those in the patients without big IGF-II (35.0+/-2.2 vs. 11.5+/-2.4). The present data indicate that IGF-II-producing tumors are not rare in NICTH, and serum big IGF-II and IGF-II/IGF-I ratio are useful for screening patients with IGF-II-producing NICTH.