Evidence for the presence of actin‐associated intercellular adhesion junctions between interstitial cells of Leydig in the ground squirrel testis

摘要

AbstractInterstitial cells of Leydig characteristically occur in clusters around blood vessels. Often these clusters remain intact when interstitial tissues are mechanically separated from other components of the testis. The presence of strong intercellular attachments is most likely one of the factors responsible for Ground Squirrel Testis Vancouver, British Columbia, Canada V6T 1Z3, maintaining the integrity of Leydig cell clusters. In many tissues, actin associated adhesion junctions commonly provide intercellular attachment. To determine if actin associated adhesion junctions are present between Leydig cells, we have used 1) immunofluorescence to probe for two components that characterize these junctions in other tissues and 2) electron microscopy to examine areas of intercellular contact for evidence of microfilament related adhesion junctions.Isolated clusters of unsectioned cells, which had been fixed and detergent extracted, were probed with the F‐actin specific stains rhodamine phalloidin and NBD‐phallacidin and with an affinity purified primary antibody raised against human platelet vinculin. In regions of intercellular contact, fluorescence staining with the actin probes was intense and appeared as a solid linear band. Similar regions also stained with the vinculin probe. In double label experiments, actin and vinculin probes were co‐distributed at sites of intercellular contact.Zones of intercellular contact, apparently similar to those detected with fluorescence microscopy, were observed a t the ultrastructural level. At these sites, subsurface filaments, interpreted by us as actin, formed a dense carpet adjacent to the lasma membrane on each side of the junction. These filaments appeared to be organized into networks rather than discrete bundles.Our observations that 1) probes for actin and vinculin codistribute at certain sites of intercellular contact and 2) a layer of microfilaments is associated with the plasma membrane in electron micrographs of these contact regions support the conclusion that Leydig cells, at least in the ground squirrel, may possess actin associated adhesion junctions similar to those described between cells of numerous other