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Transforming growth factors alpha and beta-1 are co-expressed in the uterine epithelium during early pregnancy.

Semi-quantitative immunoperoxidase light microscopy on unfixed frozen sections of rat uterus was used to examine the expression of transforming growth factors (TGF) alpha and beta before, during and after implantation. TGF beta-1 labelling was present in the lateral plasma membranes and basement membrane from day 3, steadily increased until the time of implantation on day 6 when it formed a dense apical band, but had disappeared by day 7. TGF alpha appeared in the apical epithelium, 3 days prior to TGF beta-1. Ultrastructural immunogold labelling showed the intense TGF beta-1 signal observed at the time of implantation to be present on the apical epithelial surface and microvilli and in the luminal secretions. We suggest that TGF alpha stimulates the expression of TGF beta-1 in rats, as in implanting transgenic mice, and that it is involved in extracellular matrix remodelling in the lateral plasma membranes and basal lamina to inhibit invasion and implantation and to stimulate the production of basement membrane.