The development of metabolite transfer between reaggregating Novikoff hepatoma cells

Abstract

Direct transfer of [ 3H]uridine-derived metabolites between reaggregated Novikoff hepatoma cells was monitored autoradiographically over the first 4 h following initial cell contact. The percentage of significantly labeled primary recipients increased progressively over the reaggregation period, reaching a level of more than 90% by 4 h. When reaggregation was promoted by centrifuging the cells on to a polylysine-coated slide, over 50% of the potential recipients became labeled within 15 min. Transfer was contact-dependent, required RNA synthesis in the recipients for detection, was not reduced by excess cold uridine in the medium, and did not occur when L-67 cells were used or recipients. Similar transfer of [ 3H]hypoxanthine-derived metabolites occurred between HGPRT + and HGPRT − Novikoff cells reaggregated up to 4 h. By that time, 1:1 cocultures of the two cell types incorporated 29% more hypoxanthine than expected from the number of HGPRT + cells present, implying a cooperative effect on nucleotide metabolism. The development of metabolite transfer had a time course similar to that reported elsewhere for the formation of gap junctions and for the appearance of junctional permeability to other small molecules between Novikoff cells. We conclude that the labeled metabolites were transferred via newly formed gap junctions.