A light and electron microscopic study of the periparturient bovine corpus luteum.
Corpora lutea were obtained surgically from fifteen mature Angus crossbred cows representing three experimental groups of five cows each. Cows in Group A were 180 days of gestation, cows in Group B had recently experienced parturition (<or=24 hours) and cows in Group C had recently exhibited standing estrus (<or=24 hours). Samples of corpora lutea were fixed in 10% buffered formalin and prepared for light microscopy and 2.5% glutaraldehyde and processed for electron microscopy. Luteal cells from cows in Group A were of two distinct types, large cell and small cell types. The large luteal cells of both Groups A and B were similar, with one exception. Those from cows in Group B stained less intensely and the nuclear chromatin appeared less pronounced and marginated. Small luteal cells were not readily observed in corpora lutea from Group B. In addition, there was evidence of pyknosis, karyorrhexis and mononuclear cell infiltration in corpora lutea from Group B. Luteal cells from cows in Group C were characterized by atrophy of the nucleus and vacuolation of the cytoplasm. Vascular changes consisted of endothelial cell necrosis and pyknosis of cells of the tunica media of arteries within the corpus luteum. Ultrastructurally, there were distinct differences in all groups with respect to the size and quantity of lipid droplets, the presence of electron lucent vesicles in the cytoplasm and indentations of the nuclear membrane of luteal cells. The results of this study suggest that at the time of parturition in the cow luteolysis may involve primarily small luteal cells, and that the corpus luteum may be a source of progesterone, which is likely a function of the large luteal cells.
Archbald
L F
LF
Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
Al-Bagdadi
F
F
Godke
R A
RA