Altered Clearance of Inhaled ^99mTc-Pentetate Aerosols following Exposure to Cadmium Chloride Aerosols in Ferrets

Abstract

The rate of clearance of inhaled ^99mTc-pentetate aerosols has been used as an indicator of pulmonary epithelial “permeability” in human and animal studies. In order to evaluate this technique further, groups of eight male ferrets (Mustek putorius furqj were given acute exposures to aerosols of CdCl₂ or NaCl via endotracheal tube. Serial evaluations of the thoracic clearance rate of inhaled ^99mTc-pentetate aerosols (MMAD = 0.6 μm, σ_g = 1.6) were made before exposure and at fixed time points after toxicant exposure (3 or 6, 24, 48 h, and 5 days after CdCl₂). These serial evaluations of ^99m Tc-pentetate thoracic clearance were conducted at three cadmium intake levels (3, 10, and 30 min exposure to 10 mg/m³ CdCl₂) in order to evaluate possible dose-related response relationships. The rate of thoracic clearance of Tc-pentetate was observed to be slowed at 3 h after exposure to CdCl₂ aerosol and subsequently increased to well above control rates. The time sequence observed strongly suggests that increased Tc-pentetate clearance rates are indicative of a tissue response or repair process, rather than acute lung injury. Tracheal epithelial penetration of macromolecular tracers was not observed to increase in histological evaluations following serial sacrifice.