Evidence for autocrine growth inhibition of rat intestinal epithelial (RIE-1) cells by transforming growth factor type-beta.

The proliferation of sparse cultures of RIE-1 rat intestinal epithelial cells was potently inhibited by transforming growth factor type beta 1 (TGF-beta 1), with a half-maximal effect at 10-30 pg/ml. As judged by [3H]thymidine incorporation assays, this growth inhibitory action became apparent 4-6 h after addition of TGF-beta 1 to the cells. RIE-1 cells express high-affinity (KD approximately 5.6 pM) receptors for 125I-TGF-beta 1. Affinity cross linking experiments labelled two major species of putative TGF-beta 1 receptors with M(r) values of 235,000 and 65,000. Medium conditioned by confluent cultures of RIE-1 cells contained latent TGF-beta-like activity that was activated at low pH. These findings support a model of autocrine growth inhibition of intestinal crypt cells by TGF-beta.