Detection of epidermal growth factor-urogastrone and its receptor during fetal mouse development

Abstract

Using both a radioimmunoassay and a radioreceptor assay, we have estimated the content of mouse epidermal growth factor-urogastrone (EGF-URO) in fetal mice at 111/2 to 171/2 days of gestation. Concurrently, the amount of specific EGF-URO receptor binding was determined in crude membrane fractions from the embryos. EGF-URO receptor binding is readily detected in membranes from the youngest embryos (day 11/2) and rises steadily up to parturition (18 days); the rise is more marked in embryo membranes derived from a potential target tissue, such as the maxilla and secondary palate. In the embryonic extracts, EGF-URO proved to be labile, requiring the presence of soybean trypsin inhibitor and sodium azide to stabilize the recovery of added EGF-URO in test samples. Even with added stabilizing agents, immunoreactive EGF-URO was barely detectable before day 141/2 (less than 20 fmol per embryo), whereas a substantial increase was observed from day 151/2 to 171/2 (from 70 to 200 fmol per embryo). In contrast, the radioreceptor assay detected appreciable amounts of an EGF-URO-like substance at 111/2 days (50 fmol per embryo) the values estimated by radioreceptor assay (about 0 old higher than by radioimmunoassay) also increase markedly between days 151/2 and 171/2 (on average from 500 to 3000 fmol per embryo). We conclude that during fetal mouse development there is an increase both in the receptors for EGF-URO and in a substance (presumably a fetal growth factor) that can occupy the receptor. The differences between the radioreceptor and radioimmunoassay estimates for the EGF-URO content suggest that the fetal form of mouse EGF-URO differs from the a ult molecule.Epidermal growth factor-urogastrone (EGF-URO) is a polypeptide of approximately 6000 daltons that is found in mice, in humans, and undoubtedly in a variety of other mammalian species (for reviews, see refs. 1-6). The recognized biological actions of EGF-URO are stimulation of cellular proliferation and inhibition of gastric acid secretion; in addition, the occurrence of receptors for EGF-URO in a large number of tissues, including the placenta (6, 7), and the effects of EGF-URO observed in organ cultures on the secondary palatal epithelium (8,9) suggest that EGF-URO plays an important role in embryonic development. Although the time course of the postnatal accumulation of EGF-URO in male mice has been observed [the submaxillary gland content rises to a maximum at about 50 days (10)], no detailed studies have been made in prenatal animals. Because of our interest in the effects of EGF-URO on palatal development, we have determined the content of both EGF-URO and its receptor at various stages of development. We have used both a radioreceptor and a radioimmunoassay to measure increasing levels of EGF-URO in embryos at 11/2 to 171/2 days of gestation, and we have concurrently measured increases in EGF-URO binding in membranes obtained from embryos at 12 to 14 days of gestation. MATERIALS AND METHODSPolypeptides and Antibodies. Mouse EGF-URO was either isolat...

Developmental expression of rat transforming growth factor-alpha mRNA.

“…Viewed in this light, the abnormal expression of TGFa in the transformed state is analogous to the abnormal expression of developmentally regulated onjogenes (16). Although the appearance of TGFa transcripts in embryos does not necessarily imply that these transcripts are translated to produce TGFa polypeptide, our results are consistent with the earlier observation of Nexo et al (14) that fetal mice at 11 days of gestation contained material that was capable of binding the EGF receptor but was not recognized in an EGF radioimmunoassay. Subsequently, Twardzik et al (18) showed that growth factors with some of the characteristic properties of TGFa could be isolated from 12-to 13-day-old mouse embryos.…”

“…Interestingly Nexo et al (14) found a significant rise in immunoreactive mouse EGF between days 15 and 17. This is approximately the time when in rat gestation the levels of TGFa mRNA have declined.…”

Epidermal Growth Factor in Neonatal Mouse Urine: Maturative Effect of Thyroxine

“…In accordance with these effects, EGF and its receptors are present in various tissues in the fetus and adult (1, 4, 1 1, 14,30,33). Though EGF most probably has an important physiological role, this remains undefined.…”

Recent advances in developmental genetics: Growth factors and morphogens

“…Boh EGF and its receptor continue to be widely expressed in the embryonic mouse (Nexo et al, 1980;Adamson and Meek, 19841, while particular attention has been focused on its role in the development of the teeth and palate (Partanen, 1990). The role of EGF and TGF 01 in development is, putatively, to contribute to epithelial development in many developing epithelial mesenchymal organs.…”

“…response Nielsen et al (1991) "I-EGF binding Nexo et al (1980) Blastocoel protein Dardik et al (1993) …”