Thiol levels in rat bronchio-alveolar lavage fluid after administration of cysteine esters.

1. The intraperitoneal administration of cysteine, N-acetylcysteine, the methyl, isopropyl, cyclo pentyl, neo pentyl, cyclo hexyl and tertiary butyl esters of cysteine and of cystine dimethyl ester increased the levels of total non-protein sulphydryls and cysteine in the bronchioalveolar lavage fluid and plasma of rats. In all cases the non-protein sulphydryl levels reflected the increased cysteine levels. 2. Cysteine, N-acetylcysteine, the cysteine esters and cystine dimethyl ester raised the levels of non-protein sulphydryls and hence cysteine in the bronchioalveolar lining fluid as follows: CIPE > CCPE > CME > CDME > CneoPE > CCHE > Nac > CySH > CTBE. 3. Plasma levels of NPSH were increased as follows: Nac > CySH > CCPE > CCHE > CneoPE > CIPE > CME > CDME > CTBE. 4. All except CTBE have been shown to protect against the lethal effects of inhaled perfluoroisobutene, a pyrolysis product of polytetrafluoroethene which induces a fulminating pulmonary oedema. 5. This study showed that by raising the levels of thiols in the bronchioalveolar lavage fluid (BALF), the epithelial cells lining the bronchiolar, alveolar regions of the lung could be protected against inhaled toxicants. 6. It is proposed that increased thiol levels in the BALF may contribute to the overall protection induced by these compounds by reacting with inhaled electrophiles to prevent or reduce damage to tissue in close proximity to the airways.