Monocrotaline pyrrole alters DNA, RNA and protein synthesis in pulmonary artery endothelial cells.

Administration of monocrotaline pyrrole (MCTP) to animals results in pulmonary vascular injury. Pulmonary vascular endothelium is a likely target for this pneumotoxicant. Cultured porcine pulmonary artery endothelial cells (PECs) treated with MCTP remain viable but are unable to divide and exhibit an altered morphology. Such responses raise a question about the extent to which affected cells carry out normal functions such as RNA and protein synthesis. Accordingly, the cellular activity of MCTP-treated PECs was examined in this study. PECs were treated with a single administration of MCTP or vehicle, and determinations of cell number, protein, and DNA content were made at times up to 7 days posttreatment. DNA, RNA, and protein synthesis were quantified by incorporation of [3H]thymidine, [3H]uridine, and [3H]leucine, respectively. Increases in cell number that occurred with time in the control cells were reduced in MCTP-treated cells. At 7 days posttreatment, both protein and DNA content increased above control levels. Synthesis of DNA, RNA, and protein continued in all treatment groups throughout the posttreatment period, but cells treated with high concentrations of MCTP showed less synthetic activity than controls during the initial 48 h posttreatment. By 7 days, MCTP-treated cells were producing significantly more DNA, RNA, and protein. These results indicate that cells treated with MCTP continue to synthesize DNA, resulting in an increased DNA content. In addition, treated cells continue to synthesize RNA and translate RNA into protein. Thus, cellular activity is maintained but altered substantially by MCTP exposure.