[Acute renal failure, renal artery stenosis and angiotensin-converting enzyme (ACE) inhibitor]. / Akutt nyresvikt, nyrearteriestenose og angiotensinkonvertase (ACE)-hemmer.

BACKGROUND: Acute renal failure is a well-known complication in patients with renal artery stenosis during treatment with ACE inhibitor. Renal artery thrombosis after withdrawal of ACE inhibitor has not been reported previously. MATERIAL AND METHODS: We describe a patient with acute renal failure with an unexpected course. RESULTS: A 67-year-old man was admitted with acute anuric renal failure during treatment with hydrochlorothiazide and enalapril. His blood pressure was 165/60 mm Hg. Renal ultrasound was normal. After initial rehydration and dialysis, diuresis resumed until a sudden unexpected anuric renal failure recurred on day 12. Angiography disclosed bilateral renal artery occlusion. The right renal artery was successfully opened and a stenosis was blocked and stented, and brisk diuresis ensued. Two days later hypertension accelerated, and a new invasive procedure on day 24 succeeded in opening, blocking and stenting a proximal stenosis in the left artery; a mobile thrombus was located behind the stenosis and successfully treated with intraarterial thrombolysis. Blood pressure rapidly normalized, and serum creatinine was normal on visits 1.5 and 4 months later. INTERPRETATION: General aspects and prevention of acute renal failure during ACE inhibitor therapy are discussed. Acute renal thrombosis after withdrawal of ACE inhibitor in patients with stimulated renin angiotensin system and significant renal artery stenosis may be causally related to the antifibrinolytic effects of angiotensin II and aldosterone. Endovascular reconstruction of renal artery occlusion may completely restore the kidney function.

Vascular permeability in acute triethyltin-induced brain edema studied with FITC-dextrans, sodium fluorescein and horseradish peroxidase as tracers.

In golden hamsters, a study was made on the vascular permeability changes which might take place during the formation of triethyltin (TET)-induced brain edema. For this purpose, the animals received a single intravenous (i.v.) injection of TET sulphate (5-10 mg/kg b.wt) and groups of animals were studied 4 to 24 h thereafter. By the use of a new density gradient technique based on polyvinylcoated silica particles (1), it was shown that white matter edema was present already at 4 h after the TET injection. The edema then progressed during the following 20 h. Electron microscopy revealed that fluid accumulated in myelin vacuoles of the hamsters in the same way as has been described in other animal species. The macromolecular tracer, horseradish peroxidase mol.wt 40,000 injected i.v., did not leak out of the cerebral vessels during the period when edema developed. In order to find out if the formation of edema is associated with a vascular permeability increase to other and smaller markers, we used several fractions of FITC-dextrans varying from mol.wt 3,000 to 70,000 and determined their intracerebral localization with a histotechnical procedure. FITC-dextrans, mol.wt 70,000, did not leak out of the cerebral vessels in any of the TET intoxicated hamsters during the observation period of 24 h. The same was true for most animals given the other dextran fractions. However, FITC-dextrans, mol.wt 3,000-20,000 were present outside the vessels in the edematous optic nerves and corpus callosum in a few TET treated animals taken 16-24 h after the TET injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of exudated FITC-dextrans in experimental vasogenic brain edema produced by a focal cryogenic injury.

Mice were subjected to cortical cryogenic brain injury, and FITC-dextrans (mol. wt. 20,000 or 150,000) were injected intravenously (i.v.). After a survival period of 4 h the distribution of the FITC-dextrans was determined by a histotechnical procedure described recently ( Hultstr öm et al. 1982a ). This technique is based on freeze-drying and vapor fixation to immobilize the tracer and to provide tissue fixation. In and around the cryogenic injury both tracers leaked out of the cortical and the leptomeningeal vessels and spread into the brain parenchyma. They were seen as multiple, closely apposed droplets of fluorescent material best recognized by fluorescence microscopy under high magnification. The tracers were also taken up by neuronal perikarya and in glial cell nuclei of, presumably, astrocytic origin. Our study shows that the FITC-dextran technique can be used for experimental studies on the vasogenic form of brain edema. The patterns formed by the extravasated tracers have qualitative similarities to those produced by other more commonly used tracers, such as fluorochrome-labeled serum proteins and peroxidase.

An improved Percoll density gradient for measurements of experimental brain edema. Addition of sucrose to an isotonic gradient in an attempt to balance osmotic conditions during density determinations.

Microgravimetric methods are very useful for quantitative studies on brain edema. One of the techniques available is based on a gradient made up by NaCl and polyvinyl pyrrolidone-coated silica particles (Percoll). The present study was performed to find a way of minimizing fluid shifts between the gradient and the samples. For this purpose, five Percoll density gradients containing various concentrations of sucrose in isotonic saline were prepared. Equivalent samples of normal mouse brain were then added and their second slow movement (drift) indicating interactions between the tissue and the gradient was followed. A concentration of 0.125 M sucrose eliminated the drift of the samples almost entirely. The capacity of this sucrose-containing gradient to reveal brain edema was then evaluated by comparing the density values obtained with those measured in the traditional bromobenzene-kerosene gradient as described by Nelson et al. (1971). For this purpose, we produced in the mouse an acute cytotoxic edema by triethyltin intoxication and a vasogenic edema by a cortical cryogenic injury. The two gradients showed almost identical results. We conclude, therefore, that the 0.125 M sucrose-containing Percoll gradient is a very good alternative to bromobenzene-kerosene gradients used for brain density determinations. Furthermore, Percoll gradients are very stable and contain only non-toxic ingredients.

FITC-Dextrans as tracers for macromolecular movements in the nervous system. A freeze-drying method for dextrans of various molecular sizes injected into normal animals.

A freeze-drying method has been developed by which fluorescein thiocarbamoyl dextrans (FITC-dextrans) can be localized in thin sections from nervous tissue and muscles. Labelled dextrans with molecular weights of 3,000, 20,000, 70,000 and 150,000 were injected intravenously (i.v.) into golden hamsters and samples from brain, trigeminal ganglia and sciatic nerves were examined 30 min or 4 h later. For comparison experiments were also carried out in mice and some other tracers were tested as well. The dextrans did not pass out of blood vessels in cerebral cortex and white matter. The blood vessels in the trigeminus ganglion were permeable to all of the tested compounds, i.e. even the FITC-dextran with mol.wt. 150,000. Little, if any, i.v. injected dextran could be detected in the endoneurium of sciatic nerve fascicles. Even very high concentrations of dextrans (mol.wt. 3,000 and 150,000) injected around the sciatic nerves did not penetrate the perineurium of the sciatic nerve. As compared with other tracers dextrans have the advantage that they can be obtained in a wide range of molecular sizes. With the proposed technique presented at the end of this article they can be used for studies on vascular permeability in deep tissue like brain, ganglia and peripheral nerve. The use of these tracers will probably be particularly advantageous in investigations concerning the etiology of edematous conditions.

Measurement of edema in the nervous system. Use of Percoll density gradients for determination of specific gravity in cerebral cortex and white matter under normal conditions and in experimental cytotoxic brain edema.

A method is presented by which density measurements can be performed on samples from cerebral cortex and white matter of normal and intoxicated animals using nontoxic ingredients as an alternative to the bromobenzene-kerosene technique described by Nelson et al. (1971). A continuous density gradient is prepared in a calibrated glass cylinder by using a new product, Percoll, which consists of colloidal silica particles coated with polyvinyl pyrrolidone. The gradient is stable and the same column can be used for repeated experiments over a long period of time. Interactions between the gradient media and the samples are evaluated and various methodological aspects concerning removal and handling of the tissue samples are presented. Experiments with acute triethyltin (TET) intoxication in the mouse and the hamster show that the Percoll technique can be used as an alternative to the bromobenzene-kerosene method in quantitative studies on cytotoxic brain edema.

Fluorescein labelled dextrans as tracers for vascular permeability studies in the nervous system.

Golden hamsters received i.v. injections of dextrans labelled with fluorescein isothiocyanate (FITC-Dextran). After 4 hrs samples from the cerebral hemispheres, Gasserian ganglia and sciatic nerves were fixed either by immersion in formalin or by cardiac perfusion with the same fixative. The distribution of the tracer was then studied by fluorescence microscopy of thin frozen sections. With this simple technique FITC-Dextrans could easily be detected in tissue sections. The tracers used (mol. w. 19000 and 154000) spread in the same way as fluorochrome-labelled albumin, remaining in the lumen of cerebral vessels but leaking extensively from vessels in the ganglia. FITC-Dextrans thus appear to be very useful tracers for vascular permeability studies of nervous tissue since dextrans can be obtained in a wide range of molecular weights. FITC-Dextrans can also be subjected to microscopic and quantitative studies.