EXPRESSION OF EPIDERMAL GROWTH-FACTOR (EGF) AND THE EGF RECEPTOR IN THE PORCINE OVIDUCT

The production, secretion, and localization of epidermal growth factor (EGF) and the distribution of the EGF receptor (EGF-R) were examined in the isthmus (I) and ampulla (A) of the oviducts from cyclic (C) and early-pregnant (P) gilts. Sexually mature gilts (n = 20) were divided equally into two groups: C and P. P gilts were bred twice (at 0 and 2 4 h), and all gilts were killed 48 h after onset of estrus. After remo val of reproductive tracts, oviducts were isolated, flushed, opened lo ngitudinally, divided by anatomical region, cut into 1-3-mm(3) pieces, and placed in Dulbecco's modified Eagle's Essential medium (DMEM: F-1 2+ITS [insulin, 5 mu g/ml; transferrin, 5 mu g/ml; and selenious acid, 5 ng/ml]+antibiotic). Half the tissue and medium were immediately hom ogenized end centrifuged, and the supernatant was removed. The remaini ng tissue was cultured in the medium for 24 h at 37 degrees C and 5% C O2, then prepared similarly for analysis. EGF was measured in the supe rnatant by a heterologous RIA. Concentration of EGF was expressed as n anogram/milliliter of EGF per milligram of protein in wet tissue. EGF concentrations were present in both regions of the oviducts of C and P gilts. It was greater in I than in A tissues for both C (I = 16.21 ng /ml vs. A = 13.91 ng/ml; p < 0.05) and P gilts (I = 14.27 ng/ml vs. A = 12.53 ng/ml; p < 0.10). Higher concentrations of EGF were found in I tissue of C gilts than in P gilts (C = 16.21 ng/ml vs. P = 14.27 ng/m l; p < 0.05). The media assayed from cultured explants of I and A sect ions from C and P gilts gave results that were highly correlated with those of immediately prepared tissue sections. Localization of EGF in frozen oviductal tissue sections was demonstrated by immunohistochemis try. The primary site of EGF immunostaining occurred in the epithelial cells (with highest intensity at the apical border) of both C and P g ilts. A and I tissue sections from C gilts showed localization of EGF immunostaining mainly in epithelial cells and lamina propria cells, wh ile those from P gilts stained less intensely. The presence of EGF-R w as shown by incubating tissue imprints and frozen sections with EGF-er ythrosin isothiocyanate, which revealed that EGF-R were distributed ma inly on the membranes of epithelial cells. The study indicates that EG F and EGF-R are present in oviductal epithelial cells in both C and P gilts, with the highest concentration of EGF in C gilts. These results suggest that EGF performs an autocrine/paracrine role in the porcine oviduct.