Phospholipase A2 activity in 9,10-dimethyl-1,2-benzanthracene-induced mammary tumors of rats

The activities of phospholipase A2 were compared in mammary glands from virgin and mid-pregnant rats and in 9,10-dimethyl-1,2-benzanthracene-induced rat mammary tumors. Enzyme activities were not different in the 150 000 × g pellet fractions of mammary gland homogenates from virgin and mid-pregnant rats, but enzyme activity in the 150 000 × g supernatant fraction was about twice as high in the homogenates from the mid-pregnant rat glands. Phospholipase A2 activities in the 150 000 × g pellet and supernatant fractions of homogenerates of growing tumor tissues were more than an order of magnitude higher than in the normal tissues. The elevated activity of phospholipase A2 in the tumor tissues may be related to their rapid rate of proliferation.