Apoptosis and autophagy in involuting bovine mammary gland.

Successful lactation depends on a controlled process of cell proliferation and mammary gland growth during pregnancy and cell death during involution. The main type of cell death responsible for involution of bovine mammary gland is apoptosis, but programmed cell death type II (PCD II)--autophagic cell death is also observed. The regulation of mammary epithelial cells (MEC) apoptosis occurs at three levels, the molecular regulators of autophagy have not been identified yet. There are possible correlations between both processes, because cells sharing morphological features of apoptosis and autophagy were found in involuting mammary gland. Autophagy seems to be cellular defense against starvation, when it fails, a secondary response of apoptotic cell death is triggered.