Development of the perifollicular capillary network. Autoradiographic and morphometric studies in the rabbit ovary

The published data give a report on systematic examinations on the development of the perifollicular capillary network in the theca interna in rabbit ovaries. The follicle size and the number of capillaries were investigated by means of morphometric methods. The extent of proliferation of granulosa and endothelial cells was studied autoradiographically by determining the labelling index (LI). The results show that the perifollicular capillary network is initiated only when the stratum granulosum has developed into a multilayered cell population. After that the number of capillaries increases linearly with increasing follicle size, independently of the oestrus cycle. During follicle growth at different times in the oestrus cycle the decrease and increase in the LI of granulosa cells is followed by a corresponding decrease and increase in the LI of endothelial cells several hours later. It should be noted, however, that the proliferation of endothelial cells in follicles with a diameter of 900 microns continues, although the decreasing LI of granulosa cells already indicates a reduced follicle growth. The number of labelled endothelial cells in atretic follicles decreases only after a decrease in proliferation of granulosa cells. In conclusion, it can be noted that the follicle growth and function is not influenced by variations in the number of capillaries in the theca interna. The curve of LI of granulosa and endothelial cells suggests that the granulosa cells have a certain regulatory function with respect to the growth of the capillary network in the theca interna.