GAP-JUNCTIONS BETWEEN MAST-CELLS AND FIBROBLASTS IN THE DEVELOPING AVIAN EYE

Mast cells are present in the eye of chick embryos from the 14th day o nward, displaying metachromatic granules, mainly in the iris anterior surface and pectinate ligament, Ultrastructurally these cells show ele ctron-dense granules and a few thin and short cytoplasmic projections in close contact with fibroblasts. Sometimes these contacts are extens ive, with long fibroblast projections partially involving the mast cel ls. Gap junctions between mast cells and fibroblasts are observed only in the eyes of 16- and 20-day-old embryos. These intercellular specia lizations are represented by a close apposition of cytoplasmic membran es with an extension up to 300 nm. Gap junctions between mast cells an d fibroblasts were not observed previously in vivo or in vitro, althou gh in vitro studies have shown that a number of functionally critical interactions may occur between these cells. Our morphological findings suggest that, in vivo, fibroblasts interact with mast cells and may i nfluence their maturation.