Light and Electron Microscopical Changes of Corpus Luteum during the Course of Pregnancy in Korean Native Cows

한우의 임신경과에 따른 황체조직의 광학 및 전자현미경적 변화

Corpus luteum (CL) is the primary productive organ of progesterone in pregnant cows. Progesterone levels in bovine plasma depend on the volume, weight and shape of the CL. Progesterone productions during the late stages of gestation occur both in the CL and placenta, and placentas producted more progesterone than CL on progesterone prcduction. Because division of progesterone production of these two organs is impoxxible, the CL function can not be determined by plasma progesterone levels following gestation stages. This study was carried out to evaluate histological findings on the CL spurium and CL verum, and also on the CL following the pregnant stages by histological and immunohistochemical and electron microscopical methods and then we expect to assume the functions of CL by histological findings. 1. Proliferations of luteal cells occur by day 120 of gestation, vessel hyperplasia occur by day 90 of gestation, and the walls and lumens of vessels developed by day 120 of pregnancy. 2. Sizes of CL cells increased to maximum around day 200 of gestation and similarly maintained by day 240. So these findings indicated that the function of Cl is most active around day 200 of gestation. 3. On parturation day, the number and size of luteal cells were maintained but stain intensity of the luteal cells and vessels are declined or disappeared, and fibrosis of luteal cells increased, and the vessel lumens are emptied. These findings indicate that CL is inactive. 4. In immunohistochemical findings, proliferative positive cells by PCNA antibody appeared more in number during early stages of gestation but appeared less following course of pregnant stages and not nearly appeared on day 120 of gestation. Apoptotic positive cells by TUNEL methods not nearly appeared on the early pregnant stages and a few appeared at late pregnant stages. So developments of CL proceed until day 120 of gestation and regression of CL was occurred by transform of luteal cells into fibrocytes than by luteal cell apoptosis. 5. In electron microscopical findings, the size of luteal cells increased more in CL verum than in CL spurium. During gestation stages, the size of luteal cells increased, mitochondria in the luteal cell cytoplasms densely and abundantly developed and also swelled mitochondria increased. The interspace of luteal cells are also dilated, transformation of luteal cells into fibrocytes are more number. The lumens and walls of peripheral capillaries of large luteal cells more broadened and thickened, and transformation of large and small luteal cells to fibrocytes are increased. The above findings suggest that function of pregnant CL more developed by day 120 of gestation and are most active around day 200 of gestation and similarly maintained by day 240 and are promptly regressed on paturation day.