Distribution of laminin, collagen type IV, collagen type I, and fibronectin in chicken cardiac jelly/basement membrane

Light microscopic immunolabeling studies were designed to identify and locate structural components within the cell‐free extracellular matrix which lies between the embryonic endocardial and myocardial tubes. Affinity‐purified antibodies were used to examine stage 15‐22 embryonic chicken hearts. Specimens were immunolabeled by using three different methodologies: (1) postembedding labeling of 10 μm cryostat sections, (2) preembedding labeling (en bloc) of whole hearts, and (3) postembedding labeling of ethanol/acetic acid‐fixed paraffin sections. Our results establish the spatial distribution of collagen type I and demonstrate for the first time the presence of collagen type IV and laminin in the myocardial‐basement‐membrane/cardiac jelly.