Before serum proteins reach the follicular antrum, several additional cellular layers must be crossed. Beyond the endothelium, blood proteins must traverse the theca interna, a layer composed of fibroblast-like, steroid-secreting, and transitional cells. Regulation of permeability of this layer could be similar to that of the vascular endothelium, in which intracellular microfilaments aid in contraction of thecal cells, resulting in the production of an increased distance between them that allows for passage of larger proteins.
Serum proteins must also pass through the basement membrane to enter the avascular antrum in which the oocyte is located, and there is some evidence that the LH surge may result in appropriate modifications of this layer. Upon hormonal stimulation, there is an increase in protease activity in the ovary. These proteases (i.e., collagenase, elastase, endoglycosidases, and sulfatases) have been implicated in the degradation of negatively charged proteoglycans associated with the basement membrane and the consequent increase in permeability of negatively charged proteins. buy flovent inhaler
Serum proteins passing through the basement membrane must next pass through multiple layers of the avascular membrana granulosa. This ovarian tissue is approximately 5-10 cells deep and contains an extensive gap junction network. It is not known, however, whether this layer is freely permeable to follicular fluid solutes.
In conclusion, selectivity and permeability of the ovarian blood-follicle barrier is a specific, temporally regulated process that controls entry of serum glycoproteins of the Ial family. This report confirms results of previous studies supporting the role of molecular size in blood-follicle transport. In addition, we show that net charge may play a central role in the regulation of permeability of the blood-follicle barrier.