Involvement of apoptosis and lysosomal hydrolase activity in the oviducal regression during induced molting in chickens: A cytochemical study for end labeling of fragmented DNA and acid phosphatase

Induced molting improves egg producing functions in hens. We investigated the mechanism of oviducal regression during induced molting. Involvement of apoptosis and autolysis in the oviducal regression process was analyzed by terminal deoxynucleotidyl transferase (Tdt)-mediated biotinylated deoxyuridine triphosphates (dUTP) nick end-labeling (TUNEL) and an enzyme histochemistry for acid phosphatase. Nuclei positive for TUNEL were negligible and acid phosphatase staining was weak in the oviduct of laying hens. The frequency of TUNEL-positive nuclei was significantly increased in tubular gland cells of magnum, isthmus, and shell gland 2 d after cessation of egg laying and significantly decreased thereafter. The intensity of acid phosphatase staining was gradually increased during oviducal regression and extremely high on Day 7 after cessation of egg laying. These results suggest that during oviducal regression in induced molting hens, apoptosis is induced in the earlier stage of oviducal regression and autolysis occurs thereafter; eventually, the glandular cells disappear.