CHARACTERIZATION OF THE EPIDERMAL GROWTH-FACTOR RECEPTOR IN PIG OVIDUCT AND ENDOMETRIUM

The aim of this study was to determine whether the stage of the oestro us cycle (day I, n = 5; day 6, n = 5; day 12, n = 3 gilts) has an infl uence on the expression and activity of epidermal growth factor recept or (EGF-R) in the pig oviduct and uterus. Histochemistry, cross-linkin g of I-125-labelled EGF to isolated oviductal and endometrial membrane s or on cryostat sections, and EGF-R binding assay were used to demons trate the presence of the EGF-R in a qualitative and quantitative mann er. The bioactivity of the EGF-R in the oviduct was estimated by means of a protein tyrosine kinase activity assay. This study suggests that EGF-R is widely distributed both in glandular and stromal cells of th e endometrium and in epithelial cells of the oviduct in pigs. The conc entrations of EGF-R were higher in oviductal membranes on day 1 (22.4 +/- 8.7 fmol mg(-1) protein) in comparison with day 6 (11.0 +/- 0.42 f mol mg(-1) protein; P < 0.05), but not on day 12 (16.0 +/- 2.9 fmol mg (-1) protein). The concentrations dropped similarly in the endometrium (day 1: 66.8 +/- 16.4 fmol mg(-1) protein; day 6: 39.1 +/- 3.4 fmol m g(-1) protein (P < 0.05); day 12: 38.0 +/- 14.6 fmol mg(-1) protein). The dissociation constant (K-d) showed the same pattern. These data we re supported by cross-linking of I-125-labelled EGF to a 170 kDa membr ane protein representing the EGF-R. In contrast to day 6 and 12 of the cycle, a significantly (P < 0.05) higher endogenous protein tyrosine kinase activity was observed on day 1. In summary, changes in concentr ations and functional status of the EGF-R may play a significant role in the cascade of cellular events in oviductal and endometrial tissues .