Background: Recently the pathophysiological role of endothelin (ET) has been presumed in a number of adrenal disorders such as primary hyperaldosteronism, pheochromocytoma and adrenocortical insufficiency. Aim: The aim of the present study was to evaluate circulating ET-1 levels in patients with endogenous Cushing's syndrome. Methods and results: Plasma ET-1 levels were determined by highly sensitive RIA. Thirteen untreated subjects with Cushing's syndrome were studied: eight women and five men of mean age 44.2^9.5 years (S.D.). In ten of them, Cushing's disease had been diagnosed and three had adrenal adenomas. ET-1 was 3-fold higher in the patient group than in age-matched healthy controls (n ¼ 13): 1.59^0.78 vs 0.46^0.20 pmol/l respectively, P , 0.001. In adrenal adenoma patients, ET-1 was not significantly higher than in the Cushing's disease subjects (1.84^0.67 vs 1.51^0.83 pmol/l respectively, P . 0.05). In three patients who died of severe cardiovascular complications, plasma ET-1 was significantly higher than in the remaining patients (2.34^0.35 pmol/l, P , 0.05). A positive correlation was found between the total cholesterol (6.94^1.75 mmol/l) and ET-1 levels in the patients with Cushing's syndrome: r ¼ þ0.73, P , 0.02. No correlation was observed, however, between the levels of ET-1 and blood pressure (183^37/106^18 mmHg), plasma cortisol levels (455.2^74.5 nmol/l) or urinary cortisol excretion (1463^726 nmol/24 h). The successful treatment and correction of hypercortisolism in seven patients led to insignificant reduction in plasma ET from 1.34^0.69 to 0.73^0.53 pmol/l, P . 0.05. Conclusion: Our results clearly demonstrate that the ET system is activated in Cushing's syndrome. Elevated plasma ET-1 levels probably play a role in the pathogenesis of accelerated and early atherosclerosis development in this disorder.

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We studied the topographical distribution and morphological characteristics of NADPH-diaphorase-positive neurons and fibers in the human claustrum. These neurons were seen to be heterogeneously distributed throughout the claustrum. Taking into account the size and shape of stained perikarya as well as dendritic and axonal characteristics, Nicotinamide adenine dinucleotide phosphate-diaphorase (NADPHd)-positive neurons were categorized by diameter into three types: large, medium and small. Large neurons ranged from 25 to 35 μm in diameter and typically displayed elliptical or multipolar cell bodies. Medium neurons ranged from 20 to 25 μm in diameter and displayed multipolar, bipolar and irregular cell bodies. Small neurons ranged from 14 to 20 μm in diameter and most often displayed oval or elliptical cell bodies. Based on dendritic characteristics, these neurons were divided into spiny and aspiny subtypes. Our findings reveal two populations of NADPHd-positive neurons in the human claustrum—one comprised of large and medium cells consistent with a projection neuron phenotype, the other represented by small cells resembling the interneuron phenotype as defined by previous Golgi impregnation studies.

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