The objective of this study was to determine whether uterine stromal and/or epithelial progesterone receptor (PR) is required for the antagonism by progesterone (P(4)) of estradiol-17beta (E(2)) action on expression of PR and lactoferrin in uterine epithelium. Uterine tissue recombinants were prepared with epithelium (E) and stroma (S) from wild-type (wt) and PR knockout (PRKO) mice: wt-S+wt-E and PRKO-S+wt-E. P(4) action on epithelial PR expression was studied in wt-S+wt-E and PRKO-S+wt-E tissue recombinants. E(2) down-regulated epithelial PR in both types of tissue recombinants, but P(4) blocked E(2)-induced down-regulation of epithelial PR only in wt-S+wt-E tissue recombinants. Thus, P(4) requires stromal PR to inhibit E(2)-induced down-regulation of epithelial PR. Epithelial PR is not sufficient in itself. The inhibitory effect of P(4) on lactoferrin expression was studied in 4 types of tissue recombinants (wt-S+wt-E, PRKO-S+wt-E, wt-S+PRKO-E, and PRKO-S+PRKO-E). E(2) induced lactoferrin in all 4 types of tissue recombinants. P(4) blocked E(2)-induced lactoferrin expression only in wt-S+wt-E tissue recombinants. In wt-S+PRKO-E tissue recombinants, P(4) inhibited lactoferrin expression only partially. P(4) failed to block E(2)-induced lactoferrin expression in PRKO-S+wt-E and PRKO-S+PRKO-E tissue recombinants. Thus, both epithelial and stromal PR are essential for full P(4) inhibition of E(2)-induced lactoferrin expression.