mouse mammary epithelium ( Turkington , 1969 ; Carpenter , 1978 ; Taketani and Oka , 1983 ) as well as in several in-vivo systems

By using progestin (P) and estrogen (E), the localization and characterization of both steroid receptors were examined in the submandibular gland (SMG) of 6-week-old immature castrated rats, with special reference to localization of epidermal growth factor (EGF). In the castrated male and female rats, both 3H-estradiol-17ƒÀ (3H-E2ƒÀ) and 3H-promegestone (3H-R5020) bound to SMG cytosol with high affinity and low capacity. These values were similar to those reported for other tissues. However, E-treatment after castration inhibited the specific binding. In sucrose density gradient ultracentrifugation, it was found that P receptors in both castrated males and females had a sedimentation coefficient of 7S, whereas E receptors had sedimentation coefficients of 4S and 7S. A histochemical study of the SMG of castrated male and female rats showed that the E-peroxidase complex (EPC)and P-peroxidase complex (PPC)-stained cells were predominantly located in the epithelium of the duct system including the excretory duct and the granular convoluted tubules. Few cells were located in the intercalated duct, and none were found in the acinus. EGF-immunoreactive cells were also located in the epithelium of the same tissue region as in PPCand EPC-stained sections. Moreover, E-treatment after castration inhibited the intensity of staining and immunoreactivity. These results clearly suggest that rat SMG contains specific P and E receptors which are mainly located in the epithelial cells of the duct system in which EGF-containing cells are identified. We discussed the possibility that P and E might affect EGF immunoreactivity, which reflects EGF production, through their receptors in the epithelium of the duct system. Biologically active polypeptides such as epidermal growth factor (EGF; Urogastrone in humans) and nerve growth factor (NGF) have been isolated from submandibular glands (SMG) of mice (Caramia et al., 1962; Cohen, 1960; Byyny et al., 1972), rats (Moore, 1978 ; Olsen and Nexcb 1983) and man (Cohen and Carpenter, 1975). Among these peptides, EGF stimulates cell proloferation in various cells in culture, including Received April 7, 1988 710 SAKABE et al. Endocrinol.Jaapon. October 1988 mouse mammary epithelium (Turkington, 1969; Carpenter, 1978; Taketani and Oka, 1983) as well as in several in-vivo systems (Cohen and Savage, 1974.; Carpenter, 1978). Androgen (A) is required for the maintenance of a high concentration of EGF (Barka, 1980) in SMG. It has been reported that cytosols of the SMG in mice (Takura et al., 1977; Verhoeven, 1979; Kyakumoto et al., 1986) and rats (Nemoto et al., 1985; Sato et al., 1985) contain A receptors which have similar properties to those of A-dependent tissues (Verhoeven, 1979; Sato et al., 1985). Although it has been reported that estrogen (E) suppresses (Kurachi and Oka, 1986) and progestin (P) inhibits or enhances (Bullock et al., 1975) the production of EGF by SMG, there are no data available to show the existance and localization of these hormone receptors or to correlate the receptors with EGF production in the gland. Therefore, the present study was carried out to establish the existence and localization of P and E receptors in rat SMG and to determine the precise localization of EGF immunoreactivity in the same animal tissue. Materials and Methods