A single administration of monocrotaline to rats results in pathologic alte
rations in the lung and heart similar to human pulmonary hypertension. In o
rder to produce these lesions, monocrotaline is oxidized to monocrotaline p
yrrole in the liver followed by hematogenous transport to the lung where it
injures pulmonary endothelium. In this study, we determined specific endot
helial targets for C-14-monocrotaline pyrrole using two-dimensional gel ele
ctrophoresis and autoradiographic detection of protein metabolite adducts,
Selective labeling of specific proteins was observed. Labeled proteins were
digested with trypsin, and the resulting peptides were analyzed using matr
ix-assisted laser desorption ionization mass spectrometry, The results were
searched against sequence data bases to identify the adducted proteins, Fi
ve abundant adducted proteins were identified as galectin-1, protein-disulf
ide isomerase, probable protein-disulfide isomerase (ER60), beta- or gamma-
cytoplasmic actin, and cytoskeletal tropomyosin (TM30-NM). With the excepti
on of actin, the proteins identified in this study have never been identifi
ed as potential targets for pyrroles, and the majority of these proteins ha
ve either received no or minimal attention as targets for other electrophil
ic compounds. The known functions of these proteins are discussed in terms
of their potential for explaining the pulmonary toxicity of monocrotaline.