Isolation of interstitial fluid and demonstration of local proinflammatory cytokine production and increased absorptive gradient in chronic peritoneal dialysis.

In peritoneal dialysis (PD) patients, the frequent exposure to "unphysiological" dialysis fluids elicits a chronic state of a low-grade peritoneal inflammation leading to interstitial matrix remodeling and angiogenesis. Proinflammatory cytokines are important regulators involved in this inflammatory process that ultimately leads to dysfunction of the peritoneum as a dialysis membrane. We aimed to measure the local concentrations of proinflammatory cytokines in the peritoneal interstitial fluid (IF).

Arterial remodeling and plasma volume expansion in caveolin-1-deficient mice.

Caveolin-1 (Cav-1) is essential for the morphology of membrane caveolae and exerts a negative influence on a number of signaling systems, including nitric oxide (NO) production and activity of the MAP kinase cascade. In the vascular system, ablation of caveolin-1 may thus be expected to cause arterial dilatation and increased vessel wall mass (remodeling). This was tested in Cav-1 knockout (KO) mice by a detailed morphometric and functional analysis of mesenteric resistance arteries, shown to lack caveolae.

Transvascular protein transport in mice lacking endothelial caveolae.

Caveolae are Omega-shaped vesicular structures postulated to play a role in transvascular protein transport. Studies on mice lacking endothelial caveolae, caveolin-1 knockout (Cav-1-KO) mice, indicate increased macromolecular transport rates. This was postulated to be due to the appearance of an alternative pathway.

Acute peritoneal dialysis in rats results in a marked reduction of interstitial colloid osmotic pressure.

The aim of this study was to investigate whether the interstitial colloid osmotic pressure (COP(i)) of peritoneum is of importance for peritoneal fluid reabsorption during peritoneal dialysis (PD). For testing this hypothesis, a method to isolate interstitial fluid from the peritoneal membrane and to measure the interstitial COP(i) in the normal peritoneum and directly after the initiation of PD needed to be developed and validated. Eighteen female rats were anesthetized subcutaneously in the neck region with fentanyl-midazolam (1:1).

Transvascular passage of macromolecules into the peritoneal cavity of normo- and hypothermic rats in vivo: active or passive transport?

During the last decades there has been a debate regarding whether transvascular protein transport is an active (transcytosis) or a passive (porous) process. To separate cooling-sensitive transcytosis from passive transport processes between blood and peritoneal fluid, we induced hypothermia in rats in vivo, reducing their body temperature to 19 degrees C. Control rats were kept at 37 degrees C.

Blood flow limitation in vivo of small solute transfer during peritoneal dialysis in rats.

The aim of this study was to determine whether or to what extent transperitoneal flux of small solutes is reduced at low blood flows during peritoneal dialysis (PD) in rats. Peritoneal blood flow reductions were achieved by bleeding anesthetized (300 g) rats by 25% of their blood volume. After bleeding, a 2 h PD dwell was started using standard PD fluid.

Transendothelial transport: the vesicle controversy.

The relative contribution of transcytosis vs. large pore transport to the passage of macromolecules across microvascular endothelia has been a controversial issue for nearly half a century. To separate transcytosis from 'porous' transport, the transcytosis inhibitors N-ethylmaleimide (NEM) and filipin have been tested in in situ or ex vivo perfused organs with highly conflicting results.

Transendothelial transport of low-density lipoprotein and albumin across the rat peritoneum in vivo: effects of the transcytosis inhibitors NEM and filipin.

This study was performed to investigate the mechanisms responsible for the transport of albumin and low-density lipoprotein (LDL) across capillary walls in vivo. To separate transcytosis from passive, 'porous' transport, we tested the effects of the transcytosis inhibitors N-ethylmaleimide (NEM) and filipin given intraperitoneally on the peritoneal capillary clearance of LDL and albumin in anesthetized rats undergoing peritoneal dialysis. Radiolabeled human albumin or LDL was given intra-arterially, and (51)Cr-EDTA was infused intravenously.