Scanning cytophotometric analysis of myocardial nucleic acid and chromatin changes in soman toxicated rabbits.

Myocardial nucleic acid responses were analysed in New Zealand White rabbits 20 min-1 h and 6-8 h following single subcutaneous injections of soman (20, 30, or 40 micrograms kg-1). Scanning-integrating microdensitometry was used to quantify Azure B-RNA and Feulgen-DNA (F-DNA) levels, and changes in the susceptibility of chromatin to Feulgen acid hydrolysis (F-DNA reactivity) of individual ventricular myocardial cells. With a dosage of 20 micrograms kg-1 soman, no RNA alterations were evidenced at 1 h whereas at 6-8 h myocardial cells exhibited higher RNA levels and an increase in F-DNA reactivity of chromatin. With dosages of 30 and 40 micrograms kg-1 soman there was an augmentation in RNA levels and in the acid hydrolysability of nuclear chromatin at both 20 min-1 h and 6-8 h. It is postulated that the observed cellular transformations represent a compensatory augmentation in myocardial metabolic functioning presumably in response to an increased functional demand on the ventricular myocardium. The absence of cytopathic or cytochemical evidence of impairment in nucleic acid metabolism is inconsistent with the premise that soman exerts direct cytotoxic effects on rabbit myocardium.