A sexual dimorphism occurs in liver cell proliferation following partial
hepatectomy, female liver regenerating faster than male, while a continuous excess of
choline to females shifts their growth pattern toward that of males (L. Tessitore, P. Pani and M.U. Dianzani,
Carcinogenesis, 13 (1992) 1929). In this study we have investigated (a) if the same sexual modulation occurs in a different type of liver growth,
hyperplasia induced by a direct
mitogen and (b) if the pre-administration of
choline to females is able to modulate this dimorphism. Liver
hyperplasia induced by
lead nitrate, a potent
mitogen, has also shown a peculiar sexual dimorphism in all phases of the proliferative process. In contrast with liver regeneration after partial
hepatectomy, the mitogenic action of
lead nitrate was less effective and was delayed in females as compared with males, by evaluating liver weight,
protein accumulation,
DNA synthesis and mitotic index. These results were also confirmed by the trend of liver regression by apoptosis. The apoptotic index was higher in males than in females. A prolonged administration of an excess of
choline has partially filled these sexual differences, since
choline has moved, in females, all the observed parameters (liver weight,
protein accumulation,
DNA synthesis, mitotic and apoptotic indexes) to values closer to those observed in males.