Pharmacokinetic evidence for possible renal accumulation of model organic anions in rats.

The urinary excretion and blood level kinetics of p-methylbenzoylformic acid (I) after intravenous infusion for 1 hr were studied in rats. The determined first-order half-lives were compared with those determined in studies in which a single intravenous dose of I was administered rapidly to rts that previously were infused with normal saline for 1 hr. While the blood t 1/2 or body clearance of I determined in the 1-hr infusion studies was similar to that determined in the single intravenous dose studies, the urinary of t 1/2 of I determined in the 1-hr infusion studies was significantly greater than that determined in the single intravenous dose studies. In infusion studies where the half-lives of I were determined in the presence of renal tubular secretion inhibitor, DL-tropic acid (II), the ratio of (urinary t 1/2)II present/(urinary t 1/2)II absent was almost twice the ratio of (blood t 1/2)II present/(blood t 1/2)II absent. The urinary t 1/2 value of I determined after infusion for only 10 min was intermediate between values obtained in the single intravenous dose studies and the 1-hr infusion studies. These data provide pharmacokinetic evidence to support the hypothesis that I and other organic anions temporarily accumulate in the surface-lying renal tubular cells after a single intravenous dose, but they tend to penetrate into the deeper renal tubular cells upon intravenous infusion, with depth of penetration increasing with increasing infusion time.

DNA-directed magnetic network formations with ferromagnetic nanoparticles.

We formed a DNA network embedding ferromagnetic cobalt nanoparticles with a 12-nm diameter through a nanoscale self-assembly of DNA molecules on large-scale mica surfaces (12 mm x 12 mm); we then confirmed its structural characteristics with an atomic force microscope. Moreover, noncontact magnetic force microscope measurement revealed that some embedded cobalt nanoparticles have different directions of magnetization, similar to "bits" in magnetic data storage devices.