Cytokinins are plant hormones that regulate various aspects of plant growth and differentiation. Recent studies have revealed that they may also have pharmacological effects on mammals. Among the cytokinin family, kinetin (N6-furfuryladenine) is commonly used because of its effectiveness and low cost. According to previous in vitro studies, kinetin mediates protection effects at low concentrations but promotes cytotoxicity and genotoxicity at higher concentrations. There is, however, a need for further investigation into the cytotoxicity of kinetin after prolonged treatment time in lung cells.

Consequently, the present study examined kinetin's cytotoxicity in vitro by treating WI38 (normal lung fibroblast cells) and A549 (lung cancer cell line) in different concentrations for 48 hours with kinetin. Its effect was also studied in adult albino rats treated with different doses of kinetin for 10 days. Our in vitro and in vivo results confirm that kinetin at concentrations as high as 100 nM or 1 mg/kg has no cytotoxic effect on lung cells, and can safely be used systemically without harming the lung tissues.