Intracellular distribution of endothelin-1 receptors in rat liver cells

We studied the binding of (125I)-endothelin-1 as well as that of the vasopressin analogue (125I)-[8-phenylpropionyl]-LVP to purified plasma membranes, Golgi cisternae and cell nuclei from rat liver. Cell organelles were isolated by differential centrifugation and discontinuous sucrose gradients. Endothelin-1 exhibited specific binding to plasma membranes, Golgi cisternae and nuclei, while the binding of (125I)-[8-phenylpropionyl]-LVP was restricted to the plasma membranes. The number of receptors (Bmax) and the binding constants (Kd) were determined by Scatchard analysis of competition binding studies. In all cases only one class of Et-1 binding sites could be detected. The presence of Et-1 receptors on the Golgi complex either indicates that the receptor is glycosylated within the cisternae or alternatively, there exists a recycling pathway. The unexpected finding of Et-1 receptors on highly purified nuclei suggests that this peptide may exert part of its biological functions intracellularly via the nucleus.

[Appendicitis in children]

In 1992, appendicitis is still common among children. Mortality due to a belated or erroneous diagnosis is far from being nil. The disease must always be present in the clinician's mind, and its diagnosis is purely clinical. No significant advance has been made on this subject, and clinical findings remain of paramount importance. Hospitalization for observation at the slightest doubt and emergency surgery when the diagnosis is probable are the best means of improving the management of appendicitis in children.

Evaluation of (13C)ethanol incorporation into very-low-density lipoprotein triglycerides using gas chromatography/isotope ratio mass spectrometry coupling

Gas chromatography/isotope ratio mass spectrometry (GC/IRMS) coupling was used to evaluate (13C)ethanol incorporation into plasmatic very-low-density lipoprotein (VLDL) triglycerides of three healthy human volunteers. After the perfusion of 13C-enriched alcohol, VLDL triglyceride fractions were extracted from plasma samples and prepared for the analysis of (13C)fatty acid methyl esters. The GC/IRMS coupling line, the analytical procedure and the data collection are described. The results show that ethanol itself may be used as a substrate for lipogenesis, though to a small extent: less than 10% of VLDL triglycerides may be derived from this metabolic pathway. Ethanol incorporates predominantly into myristic and palmitic acid. The small amount of sample material required for analysis, which minimizes the amount of isotope-labelled substrate required, makes this technique a valuable tool for metabolic investigations in human subjects.

[The hemodynamic effects of isradipine and nifedipine in hypertension]

Hemodynamic Effects of Isradipine and Nifedipine in Hypertension Myocardial wall tension is an important determinant of the oxygen demand, the function and the degree of hypertrophy of the left ventricle. Myocardial wall tension should be influenced more favourably by a non-cardiodepressive antihypertensive than by a potentially cardiodepressive one. Therefore, we investigated the effects of an intravenous infusion of the calcium antagonists isradipine (I; 0.4 mg; 3,5-pyridinecarboxylic acid, 4-[benzofurazanyl]-1,4-dihydro-2,6-dimethyl-,methyl-ethylester+ ++ [9CI]; CAS75695-93-1) and nifedipine (N; 2.0 mg) resp., on hemodynamics and myocardial wall tension in 12 hypertensives by an intraindividual comparison. The adrenergic reflex activation induced by vasodilation was limited by pre-medication with 0.1 mg propranolol/kg body weight (i.v.) before application of I and N. Baseline blood pressure of the patients and its changes in response to both calcium antagonists were statistically comparable, as were the left ventricular end-diastolic volumes. The end-systolic volumes, however, decreased significantly on I but not on N: before I: 69 +/- 7.0 (mean +/- standard error), after I: 61 +/- 6.1 ml, 2p less than 0,001; before N: 62 +/- 6.1, after N: 64 +/- 7.0 ml, n.s. (difference to I: 2 p less than 0.05). Stroke volume increased only on I (before I: 62 +/- 4.1, after I: 69 +/- 4.1 ml, 2p less than 0.001; before N: 64 +/- 3.5, after N: 65 +/- 3.8 ml, n.s. (difference to I: 2p less than 0.05)).(ABSTRACT TRUNCATED AT 250 WORDS)

Alzheimer's disease in Down's syndrome with SPECT

Alzheimer's disease often occurs in patients with Down's syndrome. SPECT scanning with I-123 IMP and Tc-99m HMPAO identifies decreased cerebral perfusion and metabolism in these patients at lower cost. In this case, SPECT scanning revealed changes in Alzheimer's disease in a Down's syndrome patient.

[Significance of hyponatremia in patients with oropharyngeal tumors]

We observed 29 patients with hyponatremia associated with oropharyngeal carcinoma. In 19/29 the hyponatremia was attributable to a decreased effective arterial blood volume whereas in the remainder (10/29) the presence of SIADH could be demonstrated. These etiologies of hyponatremia were best differentiated by the plasma urea concentration (less than 30 mg/dl in SIADH), urate concentration (less than 4,0 mg/dl in SIADH) and creatinine concentration (less than 0,9 mg/dl in SIADH). Furthermore, SIADH patients had a spontaneous natriuresis. The mainstay of therapy in either form of hyponatremia is fluid restriction (less than 1 l/d).

Action of aldosterone on cultured renal collecting duct cells during the latent period

The effects of aldosterone on protein synthesis in the latent period were investigated on cultured renal collecting duct cells from neonatal rabbit kidneys. Tissue was incubated with radioactively labelled uridine and amino acids and then precipitated with trichloroacetic acid in order to determine the intracellular precursor pool and identify new synthesis of RNA and protein. During the latent period, aldosterone increased the intracellular radioactive uridine pool and total radioactive RNA content already 20 and 60 min after its application; conversely 40 min after aldosterone introduction, no stimulation was found. Further experiments revealed that the intracellular radioactive amino acid pool was generally increased by aldosterone after 20, 40 and 60 min, while a distinct increased radioactive protein content was found to be induced by aldosterone only after 40 min. This indicates that aldosterone increases the uptake of RNA and protein precursors and the new synthesis of RNA and proteins. These events seem to to be regulated not continuously but intermittently. The induced proteins possibly take part in the mediation of the early hormone response. Experiments with the aldosterone antagonist, spironolactone, provide evidence for the specificity of the described hormone effects. The results after application of the Na+ channel blocker, amiloride, and the Na+/K(+)-ATPase inhibitor, G-strophanthin, indicate that the aldosterone effects are controlled by Na+ channels and Na+ pumps and therefore by the intracellular Na+ content. The inhibitory effect of cycloheximide on the aldosterone-induced protein synthesis indicates the role of these proteins on the hormone-stimulated Na+ transport.

Lithium treatment reduces the renal kallikrein excretion rate

Lithium salts are widely used agents for the prophylactic treatment of affective disorders. Lithium salts may be associated with distal nephron dysfunction. Kallikrein is a protease which is generated by the distal nephron. We used an amidolytic assay of chromatographically purified enzyme to determine the urinary excretion rate of active kallikrein in relation to lithium treatment. All plasma lithium concentrations were within the therapeutic range (0.4 to 0.9 mmol/liter). In 15 patients the urinary excretion rate of active kallikrein was 267.4 +/- 65.6 mU/24 hrs before lithium treatment, and fell to 117.8 +/- 39.6 mU/24 hrs (P less than 0.05) on day 14 of lithium treatment. This reduction was associated with a decrease of immunoreactive kallikrein in the same urines by 66%. In another 15 patients who had undergone lithium therapy for an average period of 5.6 years, the urinary excretion rate of active kallikrein was 86.1 +/- 14.5 mU/24 hrs, while 21 age-matched healthy controls had an excretion rate of 364.1 +/- 58.4 mU/24 hrs (P less than 0.05). Measurements of immunoreactive kallikrein in the same urine samples demonstrated a reduction of kallikrein after long-term lithium treatment by 78%. These observations could not be attributed to changes in creatinine clearance, renal sodium or potassium excretion rates or plasma concentrations of aldosterone and vasopressin. Addition of lithium to the urine in vitro had no demonstrable effect on kallikrein measurement by amidolytic assay. We conclude that lithium in therapeutic plasma concentrations may directly suppress the secretion of kallikrein by renal connecting tubule cells.

Osteoid osteoma of the acetabulum: two cases

We report two cases of osteoid osteoma of the acetabulum associated with severe chronic synovitis. The diagnosis is difficult and usually delayed because the acetabulum is a rare site for this tumor and clinical signs are nonspecific. Computed tomography (CT) scanning is the best diagnostic technique. An intraarticular surgical approach allows complete resection, but one case required spongy bone grafts. Postoperative results are excellent.

Cation channels in the apical membrane of collecting duct principal cell epithelium in culture

The apical cell membrane of cultured monolayers of collecting duct principal cells was investigated with the patch-clamp technique to study single ion channels. A broad spectrum of channel events was observed which complicated the analysis. Although principal cells absorb mainly Na+ ions and although most patches must have contained an Na+ conductance as evidenced by asymmetric clamp currents in the presence of amiloride, single Na+ channel events could not be identified with certainty, possibly because single-channel conductance was too low (less than or equal to 5 pS). Instead, non-selective cation channels of 21.2 +/- 4.0 pS were frequently observed. They were impermeable to choline and anions but did not discriminate between Na+ and K+. These channels, however, do not appear to participate in active Na+ absorption. Different types of K+ channels were observed: a high-conductance Ca2(+)-activated K+ channel and a bursting low-conductance K+ channel. Since the former channel has been denied a role in K+ secretion/absorption in native collecting ducts, the latter might be involved. In addition three types of Cl- channels have been observed which will be described separately. At least one of those, a 30-pS outwardly rectifying Cl- channel appears to allow small amounts of Cl- ions to be absorbed across principal cells.

[Kidney function in heart failure]

Congestive cardiac failure is a syndrome in which a decrease of cardiac output triggers a series of neuro-humoral compensatory mechanisms in part involving the kidney. In this response, dysfunction of atrial volume receptors as well as disturbances of the autonomic nervous system have recently been demonstrated and are held responsible for excessive stimulation of angiotensin II, followed by adverse regulatory effects. Renal hemodynamic compensation for heart failure primarily involves constriction of efferent arterioles thereby defending glomerular filtration. In this setting, the occurrence of prerenal insufficiency is indicative of a far advanced reduction in renal blood flow. Apparent diuretic resistance in the treatment of heart failure is usually caused by iatrogenic vascular compromise or by the use of a single diuretic rather than an appropriate combination. Hyponatremia, vasopressin stimulation and elevation of plasma N-epinephrine concentration have been found to be the most reliable indicators of a poor prognosis of heart failure. Atrial natriuretic peptide is stimulated in proportion to the degree of atrial distension in heart failure, however its intrarenal effects are markedly blunted or may even be absent in this particular disease.

Inappropriate secretion of antidiuretic hormone, polydipsia and hypothalamic calcifications

We studied a 41 year old patient who had pathologic fluid intake of 10 1/day together with syndrome of inappropriate antidiuretic hormone. Imaging studies revealed a lesion of the anterior wall of the third cerebral ventricle. A review of relevant literature indicated several different disturbances by which alterations of thirst, vasopressin-secretion and abnormalities of anterior third ventricle may be associated. The present case presents an unusual and potentially dangerous combination in this spectrum of changes.

Action of aldosterone on protein expression in cultured collecting duct cells from neonatal rabbit kidney

To investigate whether 'aldosterone-induced proteins' could be detected in mammalian species, cultured renal collecting duct epithelia from neonatal rabbit kidneys were labelled under aldosterone administration with radioactive methionine and subsequently fractionated into cytosolic and coarse membrane protein fractions. Newly synthesized proteins were then analyzed by SDS-PAGE, isoelectric focussing and two-dimensional electrophoresis. Quantitative estimates of individual newly synthesized proteins were performed utilizing gel slicing, scintillation counting and autoradiography. The labelling experiments demonstrated that, in comparison to controls, aldosterone (1 X 10(-6) M) generally increased the amount of radioactive protein. No qualitative changes in the pattern of newly synthesized proteins and, therefore, no classical aldosterone-induced proteins were observed. The increase of radioactive protein was already seen after 1, 6, and 18 h of hormone treatment. The effect could be blocked partially by spironolactone (1.5 X 10(-4) M), and totally by amiloride (1 X 10(-6) M), g-strophantin (5 X 10(-4) M), and cycloheximide (1 X 10(-6) M. Thus, the interference of aldosterone action at the receptor level, the Na+ channels and the Na+/K(+)-ATPase pump demonstrate that the expression of proteins in cultured renal collecting duct cells is a sensitive system and seems to be controlled by aldosterone at the receptor level, but also counter-controlled by specific plasma membrane sites.

Action of aldosterone on citrate synthase in cultured renal collecting duct cells

Cultured renal collecting duct cells from neonatal rabbit kidney were used to examine the influence of aldosterone on enzymatic activity of citrate synthase during increase in Na+ transport. Control epithelia showed citrate synthase activity of 71 +/- 3 mU/mg protein (n = 28), while after aldosterone treatment citrate synthase activity was significantly increased to 79 +/- 6 mU/mg at 1 h (n = 5), to 88 +/- 6 mU/mg at 2 h (n = 6) and to 93 +/- 8 mU/mg protein at 3 h (n = 5). Citrate synthase activity subsequently decreased to basal values. Spironolactone fully blocked the aldosterone-induced increase in citrate synthase activity. The time course of enzyme stimulation after aldosterone administration indicates that the hormone activates citrate synthase during the physiological early response phase.

Natriuretic factors and lithium clearance in patients with the syndrome of inappropriate antidiuretic hormone (SIADH)

Because the syndrome of inappropriate antidiuretic hormone (SIADH) is a state of disturbed body fluid volume regulation and altered sodium balance we sought to determine if recently described volume regulatory factors were stimulated in SIADH. We measured atrial natriuretic peptide (ANP), endogenous digitalis-like natriuretic factor (EDNF) and urinary free dopamine in SIADH (n = 27). We also determined fractional clearance of lithium (FCLi). The data obtained in SIADH were compared with similar measurements performed in sodium retaining hyponatremias, such as those of heart failure (n = 26), liver cirrhosis (n = 19) and volume contraction (n = 28). We observed: ANP was 19.5 +/- 2.7 fM/ml in SIADH; it was significantly lower than ANP in cardiac failure, but no different from ANP in volume contraction. Urinary free dopamine was 2.2 +/- 0.8 microM/24 h in SIADH; this was significantly higher than in volume contraction and liver cirrhosis. EDNF (259 +/- 42 nM/24 h) and FCLi (21.4 +/- 2%) were both numerically higher in SIADH than in other hyponatremic disorders; however, the differences did not achieve significance. In conclusion, our observations did not establish a specific role of ANP in chronic stable SIADH. As to the importance of EDNF, dopamine and proximal tubular fluid reabsorption (FCLi) additional work using acute volume changes may demonstrate their participation in the renal sodium handling of SIADH more clearly than our study did.