GSNO and HEL cell endonucleosomal DNA cleavage.

(A) Autoradiographic analysis of total cellular DNA prepared from HEL cells after treatment with 100 μmol/L GSNO for different times and 3′-end labeled (1 μg DNA/lane). The characteristic endonucleosomal fragmentation of DNA into 185-bp multiples is visible as early as 30 minutes after treatment with 100 μmol/L GSNO. 1, Untreated HEL cells; 2, HEL cells treated with 100 μmol/L GSNO for 30 minutes; 3, for 1 hour; 4, for 2 hours; 5, for 3 hours; 6, for 4 hours; and 7, for 5 hours. (B) Autoradiographic analysis of total cellular DNA prepared from HEL cells after induction of endogenous iNOS, as described in “Materials and methods.” 1, Cytokine induction of iNOS; 2, cytokine induction of iNOS in the presence of L-NMMA.