Capillary sprouts in ovaries of immature superstimulated golden hamsters: a SEM study of microcorrosion casts.

A new polyester resin of low viscosity was used to study the three-dimensional structure of capillary sprouts of mature follicles and of corpora lutea. Vascular microcorrosion casts were obtained from ovaries of immature golden hamsters between days 4 and 7 after stimulation with pregnant mares' serum gonadotrophin (PMSG). On days 4 and 5 after PMSG, a nodular appearance of the organ was due to mature follicles and corpora lutea. Capillary sprouts were seen as dead-ending structures originating from the thecal capillary network. The sprouts were either concentrated around (follicle type 1) or towards (follicle type 2) the center of the antrum. Increased vascular permeability resulted in resin leakage only in type 2. Intact corpora lutea were characterized by radially grown capillary sprouts. Regressing corpora lutea showed a marked reduction of the vascular bed as displayed by filling defects in casts on day 6 and 7 after PMSG. It is assumed that: 1. Dead-ending capillary structures, resin leakage, and filling defects are not always artifacts of the microcorrosion cast technique, but can express functional microcirculatory changes. 2. The concentric growth of thecal capillary sprouts may be related to the presence of an intact follicular basal membrane, and the radial growth of sprouts be taken as a sign of a digested basal membrane.