Whole-body autoradiographic studies in rats with gadolinium-diethylenetriaminepentaacetic acid, a new contrast agent for magnetic resonance imaging.

The time course of the distribution of radiolabel in organs and tissues was investigated after intravenous administration of 0.5 mmol/kg of 14C-labelled gadolinium-diethylenetriaminepentaacetic acid (Gd-14C-DTPA) and of 153Gd-DTPA to pregnant rats (18th day p.c.) and after intragastric administration of 30 mumol/kg of Gd-14C-DTPA to male rats by whole-body autoradiographic technique. After intravenous administration Gd-DTPA was rapidly distributed within the organism. The distribution pattern was similar to that of classical X-ray contrast agents like diatrizoate and iotalamic acid. Gd-DTPA was not able to pass blood-brain and placental barriers. There was no indication of a dissociation of Gd-DTPA complex. 24 h after i.v. injection most of the radiolabel left the body. Only very small amounts were found in the kidney, the placenta and in the contents of the intestine. No specific and long-lasting retention of radioactivity was observed in any organ and tissue. After intragastric administration Gd-DTPA was not absorbed.