Apoptotic cell death, bax and bcl-2 expression during sheep mammary gland involution

Involution in ovine mammary tissue was studied by light and electron microscopy\ and bax and bcl!1 protein distribution was examined by immunohistochemistry from the last day of lactation until the 7th day of drying o}[ The mammary gland alveoli were examined and the area of glandular epithelium was evaluated morphometrically[ Regression of mammary gland epithelium by apoptosis was _rst identi_ed 1 days after the end of lactation\ and increased until day 7[ Bax protein was detected throughout this period and was highest on the eighth day[ A weak positive reaction for bcl!1 was observed only on days 0 and 7 after cessation of lactation[ It is concluded that sheep mammary gland involution involves cell death by apoptosis and that bcl!1 gene family members are involved in the process[