The staining was not likely to be nonspecific, as Western immunoblot analyses of dissected follicles using the same antibodies produced bands only at the expected molecular weights for type IV collagen a chains, namely NC1 dimers (54 kDa) and monomers (28 kDa). Furthermore, staining patterns similar to those observed in the current study were reported by Bagavandoss et al. using an antibody to the EHS sarcoma type IV collagen; a1(IV) and a2(IV) are found in the EHS sarcoma. Widespread staining in the theca interna has also been observed for laminin using antibodies directed against either the EHS laminin, which contains the a1, (32, and 71 laminin chains, or against the 71 chain alone. It is possible that the collagen a1(IV) and a2(IV) chains and the laminin 71 chain are present as free molecules in the theca interna, as there are no recognized conventional basal laminae in these regions. However, it is also possible that this staining is associated with small fragments of basal lamina-like electron-dense material found extracellularly in the theca. This material has been observed at the electron microscope level in the theca of sheep, rats, and cows (see Fig. 1). The origins and functions of this thecal matrix are not known. antibiotic levaquin
From our studies, we conclude that the composition of the follicular basal lamina changes during the course of follicle growth and development. We believe, but have still to prove, that these changes reflect changes in the function of the follicular basal lamina, particularly in filtration properties and their ability to regulate functions of granulosa cells. We have also to determine for type IV collagen (and also laminin) how the individual chains are combined in each molecule and whether this also changes with follicle development. The large amounts of a1(IV) and a2(IV) present in the matrix of the thecal layer of the follicle are not associated with the follicular basal lamina or the basal laminae of the vasculature. The role of this matrix in the differentiation of thecal cells or other functions has still to be determined.