IN-SITU DETECTION OF APOPTOSIS IN REGRESSING CORPUS-LUTEUM OF PREGNANT SOW - EVIDENCE OF AN EARLY PRESENCE OF DNA FRAGMENTATION

Luteolysis has been shown to be correlated with apoptosis in rats, she ep, and cows. In pigs, apoptosis has already been demonstrated as rega rds atretic follicles. The present study has been conducted to evaluat e whether apoptosis occurs during corpora lutea regression in the preg nant pig and to investigate the temporal relationship between apoptosi s and functional luteolysis. The apoptotic process has been studied th rough the research of oligonucleosome fragmentation by means of classi cal electrophoresis methods and by in situ detection on histological l uteal sections. The latter method allows the identification of apoptos is and the localization of apoptotic cells. Pregnant sows were clopros tenol (PGF(2 alpha) analog) treated and ovariectomized 0, 6, 12, 24, 4 8, and 72 hr after treatment. Corpora lutea were utilized for progeste rone and DNA extraction and in situ evaluation of apoptosis. Clear evi dence of apoptosis was seen earlier with the in situ technique (6 hr f or stromal tissue, 12 hr for luteal cells) than with the classical met hod (24 hr). Apoptosis was, however, apparent after plasma and tissue progesterone had reached basal levels. In conclusion, these results ar e consistent with the hypothesis that apoptosis occurs during luteolys is in pigs. Moreover, the data obtained with the in situ technique mad e it possible to identify signs of structural regression in stromal ti ssue first than in parenchymal cells. A two-stage activation of apopto sis has been discussed to explain structural changes that occur during luteolysis after cloprostenol treatment in swine corpora lutea.