A method for measuring DNA damage and repair in the liver in vivo.

SUMMARY Alkaline sucrose gradients were used to study the induc tion of single-strand breaks in and repair of rat liver DNA in vivo. Liver DNA was labeled during regeneration after partial hepatectomy. DNA was isolated from the organ in such a way as to minimize the induction of breaks due to handlingor enzymaticactivity.Differentmethodsof prepar ing high-molecular-weight liver DNA were compared. Best results were obtained by squashing the liver in an ethylene diaminetetraacetic acid-sodium chloride buffer. Using this squash technique and alkaline sucrose gradients, high-mo lecular-weight DNA was regularly obtained. This DNA be havedlike single-stranded DNA onhydroxyapatite columns and contained no detectable contamination of protein or RNA. It was demonstrated by the method described that hepatic DNA damage was produced within four hr by the administration of methyl methanesulfonateand that the rat can repair such hepatic DNA damage in vivo within 48 hr.