Microcorrosion casts of hamster luteal and follicular vasculature throughout the estrous cycle.

Golden hamster (Mesocricetus auratus) ovarian microcorrosion casts were studied as a model system to analyze angiogenesis that occurs in the corpus luteum (CL) during the estrous cycle. Growth of the vasculature in the hamster CL occurs rapidly with complete formation and subsequent degeneration occurring during the 4-day estrous cycle. This study followed the growth of these vessels by casting the ovarian vasculature at 4-hour intervals during the formation of the CL, viewing the casts on a Scanning Electron Microscope (SEM), and comparing the consecutive casts. This study revealed that the microvasculature of the CL forms rapidly from the vessels of the theca folliculi of newly ruptured follicles and that this growth is in an internal direction. This method of casting, when used in conjunction with the high magnification provided by the Hitachi field emission high resolution SEM, enabled us to analyze the growing tips of the vascular sprouts. The vasculature of the CL grows throughout day 1 and well into day 2 of the cycle. Flat veins, characteristic of the external surface of a mature CL, formed by the afternoon of day 2. Obvious degeneration of the vasculature of the CL took place throughout day 3. This study provided a detailed description of the angiogenesis that occurred throughout the rapid formation of the hamster CL and showed that this method produced casts of suitable quality for experimental observations.