  This study describes the distribution of intravenously injected polyacrylic
acid (PAA) coated {\gamma}-Fe2O3 NPs (10 mg kg-1) at the organ, cellular and
subcellular levels in healthy BALB/cJ mice and in parallel addresses the
effects of NP injection on kidney function, blood pressure and vascular
contractility. Magnetic resonance imaging (MRI) and transmission electron
microscopy (TEM) showed accumulation of NPs in the liver within 1h after
intravenous infusion, accommodated by intracellular uptake in endothelial and
Kupffer cells with subsequent intracellular uptake in renal cells, particularly
the cytoplasm of the proximal tubule, in podocytes and mesangial cells. The
renofunctional effects of NPs were evaluated by arterial acid-base status and
measurements of glomerular filtration rate (GFR) after instrumentation with
chronically indwelling catheters. Arterial pH was 7.46 and 7.41 in mice 0.5 h
after injections of saline or NP, and did not change over the next 12h. In
addition, the injections of NP did not affect arterial PCO2 or [HCO3-] either.
Twenty-four and 96h after NP injections, the GFR averaged 11.0 and 13.0 ml
min-1 g-1, respectively, values which were statistically comparable with
controls (14.0 and 14.0 ml min-1 g-1). Mean arterial blood pressure (MAP)
decreased 12-24h after NP injections (111 vs 123 min-1) associated with a
decreased contractility of small mesenteric arteries revealed by myography to
characterise endothelial function. In conclusion, our study demonstrates that
accumulation of superparamagnetic iron oxide nanoparticles does not affect
kidney function in healthy mice but temporarily decreases blood pressure.
