Iron accumulation in the substantia nigra in rats visualized by ultrasound

In recent studies, we have found a marked increase in substantia nigra (SN) echogenicity in patients with Parkinson's disease (PD) using transcranial ultrasound. Because a substantial body of evidence has accumulated indicati ng a selective elevation of iron in the SN from patients with PD, we set ou t to test the hypothesis that trace metals like iron could lead to the obse rved increase of SN echogenicity in PD, Rat brains were scanned after stere otactic injection of iron in different concentrations into the SN and after injecting ferritin, zinc and 6-OHDA alone, and after the addition of desfe rrioxamine. The amount of iron in the SN was measured spectroscopically. Fo r iron, and partly for 6-OHDA, in different concentrations, a dose-dependen t increase of SN echogenicity could be visualized, corresponding to an incr ease of iron measured by spectroscopy. No increase of echogenicity was visu alized after the injection of ferritin and the addition of desferrioxamine to 6-OHDA, though an increase of iron was measured by spectroscopy. Therefo re, we conclude that iron not bound to these proteins may lead to an increa se of echogenicity of the SN. (C) 1999 World Federation for Ultrasound in M edicine & Biology.