The composition of a basal lamina markedly affects its ability to filter material and affects the fate of adjacent epithelial cells. Therefore, basal laminae differ in composition with tissue development, and between different tissues in the body. Laminins are a component of basal laminae and consist of one a, one β and one γ chain, of which there are at least five, three and two isoforms, respectively. This is the first study to immunolocalize a range of these individual laminin chains (α1, α2, β1, β2, γ1) in ovarian follicles. Frozen sections of bovine ovaries (n = 6) were immunostained using specific antisera to laminin chains and factor VIII-related antigen (to identify endothelial cells). Secondary antisera were labelled with one of two different fluorochromes (DTAF and Cy3), and dual localization of laminin chains and factor VIII-related antigen was performed. The α1, β2 and γ1 chains were consistently localized to the follicular basal lamina in all healthy follicles. Staining was less intense in the atretic antral follicles. Conversely, α2 and β1 were rarely present in the follicular basal laminae of healthy antral follicles. Two of nine healthy antral follicles observed stained weakly for α2 in their basal lamina, and β1 was present at low concentrations in growing preantral follicles. In atretic antral follicles, the follicular basal lamina stained positively for α1, α2, and β2 but no β1 was detected and the γ1 staining was less intense than in healthy follicles. Antisera to Englebreth Holm-Swarm tumour laminin stained basal laminae of all follicles. In the theca of antral follicles, β1 and β2 chains were both present in the vasculature. Staining for the γ1 chain was present in the thecal vasculature and generally throughout the theca of healthy and atretic antral follicles. Therefore, the composition of the follicular basal lamina alters during development and atresia, and potentially plays a role in the changing identity of the granulosa cells and the accumulation of antral follicular fluid.
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