Sex differences in response to four promotion regimens in spite of common first cellular steps in the hepatocellular cancer process initiated by diethylnitrosamine.
Female adult rats were as responsive as males to initiation by diethylnitrosamine (DEN) as measured by numbers of GST-P positive hepatocytes appearing early, and do develop hepatocellular cancers. However, when females and males were exposed to four promotion regimens including orotic acid (OA), choline deficiency, deoxycholic acid (DOC), or selection for resistance (to 2-acetylaminofluorene; 2-AAF) after DEN initiation, very significant sex differences were observed with respect to oval cell proliferation and growth rates of hepatocytic foci. These results suggest that responses to promotion such as growth of foci and oval cell proliferation can accompany carcinogenesis but may not be essential to the development of hepatocellular cancer.