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ABSTRACT
The concentrations of epidermal growth factor (EGF) were measured by radioimmunoassay in the submandibular gland, plasma and urine of adult female C3H/HeN mice whilst virgin and during pregnancy, lactation and after lactation. During gestation there was a significant increase in the submandibular EGF concentration which was five to seven times higher than that found in virgin mice. The level of EGF in the gland remained high during the period of lactation and even several weeks after lactation. Plasma EGF levels were also increased during the periods of pregnancy, lactation and after lactation when compared with those of virgin mice. These increases were, however, apparent only between 24.00 and 08.00 h, because of circadian variations in circulating EGF. The level of plasma EGF was significantly (P<0·05) higher during the 24.00–08.00 h period than during the 12.00–20.00 h period in all stages examined. Concentrations of EGF in the urine of virgin, pregnant, lactating and primiparous mice remained relatively constant, and the levels were much higher than those in the plasma. Similar studies using sialoadenectomized pregnant and lactating mice indicated that the plasma levels of EGF were below the level of sensitivity of the assay (<16·5 pmol/l (<0·1 ng/ml)) even during the 24.00–08.00 h period, whereas urinary EGF remained at high levels which were similar to those of normal pregnant and lactating mice. These results suggest that submandibular EGF contributes to the increase in plasma EGF which occurs after gestation, but is not the major source of the urinary EGF.
J. Endocr. (1985) 106, 197–202
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ABSTRACT
The concentration of epidermal growth factor (EGF) in the submandibular gland of immature female mice (less than 6 weeks old) was low, ranging from 0·07 to 0·17 pmol (0·4 to 1·0 ng)/mg wet wt, but increasing to 7·61 pmol/mg wet wt by 8 weeks of age. It remained relatively constant up to 24 weeks of age, but thereafter the glandular EGF concentration increased again during the post-reproductive period to reach 62·9 pmol/mg wet wt. In contrast, the glandular EGF content in male mice increased greatly during the first 17 weeks of age to about 310 pmol/mg wet wt, and thereafter remained relatively constant up to 48 weeks of age. Ovariectomy of mature virgin mice markedly increased the glandular concentration of EGF to about 74·4 pmol/mg wet wt 4 weeks after the operation. This increase was suppressed by oestradiol-17β administered to ovariectomized mice at a dose of 1 μg/mouse per day but not by 1 mg progesterone. Histological studies indicated that granular convoluted tubular cells that produced EGF in the submandibular gland were much less abundant in 12-week-old female and in oestrogen-treated ovariectomized mature mice than in 40-week-old female and ovariectomized mature mice. We conclude that oestrogen suppresses the concentration of EGF in the submandibular gland of female mice.
J. Endocr. (1986) 109, 221–225
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The levels of mRNA for long and three short forms of prolactin receptor (PRLR) were examined in the livers of normal (db+/db-) and insulin-resistant diabetic (db+/db+) mice to assess the role of gonadal steroid hormones in the regulation of PRLR gene expression in diabetes mellitus. In females, plasma levels of testosterone in diabetic mice were higher, and those of 17beta-estradiol were lower when compared with levels in normal mice. By contrast, diabetic male mice had lower plasma levels of testosterone than normal males and showed no significant difference in the low circulating level of 17beta-estradiol compared with normal males. The short 3 form of PRLR (PRLR3) mRNA was the most abundant in the liver of both normal and diabetic mice. In addition, the level of PRLR3 mRNA in normal females was 8-fold higher than in normal males. The level of PRLR3 mRNA in diabetic females was approximately a quarter lower than in normal females, whereas the level of PRLR3 mRNA in diabetic males was approximately 2-fold higher than in normal males. During postnatal development, the level of PRLR3 mRNA increased during puberty in normal females, while the level in diabetic females decreased to a nadir at 7 weeks of age followed by a progressive rise. On the other hand, the levels of PRLR3 mRNA in both normal and diabetic males decreased gradually during 5 to 14 weeks of age. Testosterone treatment of diabetic males and females resulted in a 49.1 and 49.8% decrease of PRLR3 mRNA respectively. 17beta-Estradiol treatment slightly (18%) increased levels of PRLR3 mRNA in diabetic males. These results suggest that the hepatic level of PRLR mRNA is regulated by the inhibitory effect of testosterone and the stimulatory effect of estrogen in both normal and diabetic mice.
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ABSTRACT
The role of epidermal growth factor (EGF) in liver regeneration was studied in mice after partial hepatectomy. Two weeks before partial hepatectomy, mice were sham-operated (control) or sialoadenectomized (removal of submandibular glands) to reduce plasma EGF levels. Sialoadenectomized mice showed low plasma EGF levels (29·7 ±6·6 pmol/l; mean ± s.e.m.) compared with controls (66·0±8·3 pmol/l). After partial hepatectomy, sialoadenectomized mice were treated with or without a daily s.c. injection of 5 μg EGF and the rate of DNA synthesis in the regenerating liver was monitored by [125I]iododeoxyuridine uptake. Control mice showed a sharp peak of DNA synthesis at 48 h after partial hepatectomy while sialoadenectomized mice showed a delayed and broad peak at 84 h. Treatment of sialoadenectomized mice with EGF (5 μg/mouse per day) completely restored the pattern of DNA synthesis so that a sharp peak appeared at 48 h. The total liver DNA content of the control mice (79·1±2·5% of the preoperative level; mean ± s.e.m.) was significantly (P < 0·01) higher than that of the sialoadenectomized mice (65·2±3·0%) 3 days after partial hepatectomy, but this difference disappeared on day 7 when liver regeneration was almost completed in both groups. Treatment of sialoadenectomized mice with EGF increased total liver DNA content (78·2±2·9%) to that of control mice on day 3 after partial hepatectomy. In addition, normal mice showed a rapid increase in plasma EGF levels at 1–8 h after partial hepatectomy, whereas sialoadenectomized mice showed low plasma EGF levels throughout the course of the experiment. These results suggest that EGF derived from the submandibular glands plays a role in promoting the early stage of liver regeneration.
Journal of Endocrinology (1991) 128, 425–431
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ABSTRACT
Epidermal growth factor (EGF) levels in the submandibular glands and plasma are increased in pregnant and aged female mice. The possible role of EGF in fertility was studied in virgin and pregnant mice ranging in age from 10 to 90 weeks of age, employing sialoadenectomy, administration of EGF antibody and EGF replacement. The uterine weight in pregnant, 10-week-old, sialoadenectomized mice was significantly less than in normal mice and the administration of EGF antibody to these mice further decreased uterine weight, resulting in an increased rate of abortion. Replacement EGF treatment in the sialoadenectomized mice prevented these changes. Uterine weight was about 70 mg at 10 weeks of age, and significantly increased from 30 to 80 weeks when it reached a plateau level of 275 mg. These changes closely followed the increase in the concentration of EGF in the submandibular glands and plasma and coincided with the decline in fertility. In contrast, uterine weight in the sialoadenectomized mice decreased immediately after the operation and remained at about 50–60 mg throughout the experimental period. Pregnancy, as judged by implantation, was achieved in the sialoadenectomized mice at later ages than in the controls. These findings suggest that elevated EGF levels may have a dual function in the control of fertility via uterine growth, depending on the age of mice.
Journal of Endocrinology (1993) 138, 437–443
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ABSTRACT
Epidermal growth factor (EGF) was present at a mean concentration of 266±18 (s.e.m.) pmol/mg wet tissue in the submandibular gland of 3-month-old male mice; it was also present in plasma at a concentration of 364±149 pmol/l. Sialoadenectomy (removal of the submandibular glands) decreased the plasma EGF content to undetectable levels (< 16·5 pmol/l), lowered the concentration of EGF in the skin from 1·22±0·11 to 0·47±0·08 fmol/mg wet tissue and reduced the thickness of the epidermis from 28·9±2·7 to 11·0±0·8 μm in 3 weeks (P < 0·001). Epidermal growth factor antiserum given to sialoadenectomized mice further decreased the thickness of the epidermis to 8·3 ±0·6 μm. No appreciable change was observed in the dermis and subcutaneous tissue. In sialoadenectomized mice, replacement of EGF prevented the decrease in thickness of the epidermis in a dose-dependent manner when started immediately after the operation. Treatment with EGF also effectively restored the normal morphology of the epidermis when its thickness had declined to its lowest level. These results suggest that EGF plays a physiological role in the maintenance of the epidermis.
J. Endocr. (1987) 113, 193–197
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ABSTRACT
The effects of androgen and thyroid hormones on epidermal growth factor (EGF) synthesis in the submandibular gland and on plasma EGF concentrations in mice were examined. Testosterone propionate was administered alone or in combination with l-thyroxine (T4) to female mice for 2 weeks. The submandibular EGF concentrations were increased by the administration of testosterone propionate in a dose-dependent fashion; the maximal increase, 20-fold, being produced by a dose of 2 mg every other day. The EGF levels were increased sevenfold by T4, which also enhanced the stimulatory effect of suboptimal doses of testosterone propionate. Cyproterone acetate, an anti-androgen, inhibited the testosterone propionate-induced increase, but not the T4-induced increase. Plasma EGF concentrations were raised by testosterone propionate but not by T4. Both hormones stimulated the accumulation of 4·7 kb preproEGF mRNA in the submandibular gland, which occurred almost in a parallel manner with the increase in submandibular EGF concentrations. These results suggest that EGF synthesis in the submandibular gland is regulated by alterations in the level of its mRNA by thyroid hormones and androgen, and that the rise in plasma EGF concentrations is under the influence of androgen but not of thyroid hormones.
Journal of Endocrinology (1989) 121, 269–275
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Abstract
Glucose plays an important role in fetal development and energy metabolism. Facilitative glucose transporter-1 (GLUT1) has been found in placenta. However, little is known about GLUT1 modulation in placental cells. To examine changes in mouse placental GLUT1 levels caused by 8-bromo-cAMP, we performed 2-deoxyglucose uptake experiments, Northern blot analysis and immunoblot analysis using a primary mouse placental cell culture. Immunohistochemical analysis showed that GLUT1 was localized to the ectoplacental cone and the labyrinth zone of mouse placentas on days 7 and 11 of pregnancy respectively. Treatment of mouse placental cells with 250 μmol/l 8-bromo-cAMP resulted in a significant (P<0·01) decrease in glucose uptake on days 2–5 of culture. The inhibitory effect of 8-bromo-cAMP on glucose uptake was concentration-dependent. Glucose uptake was also inhibited by 100 μg/l cholera toxin and by 0·1 mmol/l forskolin. Northern blot and immunoblot analysis revealed that both GLUT1 mRNA and protein levels were also decreased by 8-bromo-cAMP. These findings suggest that 8-bromo-cAMP inhibits glucose transport activity in mouse placental cells in culture.
Journal of Endocrinology (1996) 150, 319–327
