Specific factors influencing histotypic aggregation of chick embryo hepatocytes

Conditions are described for the reproducible assay of substances affecting the in vitro rate of aggregation of isolated chick embryo hepatocytes. Two low molecular weight (less than 1000) fractions--one that promotes hepatocyte aggregation (HAP) and the other that inhibits this stimulation (HAI)--have been isolated and partially purified from adult chicken liver. One major active component of HAP was identified as taurine (2-aminoethanesulfonate). The presence of HAP during the entire time of assay was required for largest aggregate formation. HAP had no effect on aggregation of chick embryo neural retina, kidney, or heart cells. Our results and the fact that puromycin completely inhibits aggregate formation suggest that HAP and HAI influence the specific synthesis and interaction of membrane macromolecules involved in the aggregation process.