The Mitogenic Effects of Transforming Growth Factors 1 and 2 in C3H/1 OT1h Cells Occur in the Presence of Enhanced Gap Junctional Communication’

Abstrad It has been proposed that the transfer of growth regulatory signals via gap jundions is important in the control of proliferation. In confluent 1 01#{189} cells, growth control is enhanced by retinoids; this adion is highly correlated with up-regulated gap jundional communication (GJC). Treatment of quiescent 1 0T#{189} cells with transforming growth fador (TGF) flu and TGF-fi2 resulted in elevated levels of proliferation together with increased expression of connexin43 protein and elevated GJC. Connexin43 was localized into plaques in regions of cell-cell contad; such plaques were found at high frequency in treated cells but only rarely in control cultures. These data illustrate that increased cell proliferation can occur in the presence of enhanced GJC, a result at variance with our previous results with retinoids. We suggest that either the proliferative stimulus of TGF-1J is sufficient to overwhelm any antiproliferative effed of GJC or that under conditions of TGF-fi stimulation, jundions convey net proliferative stimuli.