Characterization of single-stranded regions in DNA from injured tissue

The objective of this study was to characterize the previously demonstrated decrease in the molecular weight of DNA from kidneys submitted to storage injury. DNA from kidneys stored at either 0 degrees C for 24-96 hr or 37 degrees C for 1-3 hr underwent limited hydrolysis when incubated with S1 nuclease, an enzyme which specifically degrades single-stranded DNA. For warm-storage injury (37 degrees C), the susceptibility of the DNA toward S1 nuclease hydrolysis increased progressively with storage time. In the case of cold-storage injury (0 degrees C), a maximum degree of single strandedness was observed in the DNA representing 60 hr of storage. DNA from kidneys stored for 72 hr or longer was a poor substrate for S1 nuclease. Additionally, the nucleotide composition of the single-stranded regions was analyzed by high-performance liquid chromatography (HPLC). The results showed that single-stranded regions initially rich in dA and dT are formed during warm-storage injury. No such favoritism for a particular base was observed in single-stranded regions produced during cold-storage injury. The data suggest that both warm- and cold-storage injury promote DNA degradation. The storage temperature apparently dictates the mechanism(s) by which the degradative process proceeds.