Lasse Raaberg

Fetal Effects of Epidermal Growth Factor Deficiency Induced in Rats by Autoantibodies against Epidermal Growth Factor

We have used rats with epidermal growth factor (EGF) autoantibodies to study the role of EGF deficiency during perinatal development. The study was focused on organs known to contain EGF or its receptor. Compared with controls, the offspring of autoimmune rats had a higher perinatal mortality and a lower birth weight. The weight of the lungs was particularly low in the offspring of EGF-immunized rats, and morphologically the lungs from the surviving pups seemed atelectatic and had alveolar duct dilatation, which indicates mild respiratory distress syndrome. Judged from immunohistochemical studies, the amount of surfactant protein-A was decreased, suggesting a delayed lung maturation. The offspring of EGF-immunized rats had dry and wrinkled skin. The skin was thin and the hair follicles were immature. This suggests a role for EGF in the growth and development of the skin. The liver/body weight ratio was lower in pups from EGF-immunized rats. This difference was, however, not significant (p = 0.07), but flow cytometric analyses showed a significantly lower proportion of the liver cells from newborn EGF-deficient pups to be in S-phase and indicated that these cells were larger than liver cells from controls. To study possible alterations in EGF binding, 125I-EGF was injected i.v. in newborn rats. 125I-EGF bound in all the organs investigated. The binding is listed in decreasing order: liver, gut, skin, kidney, and lungs. In the pups from EGF-immunized rats, the lungs and the skin bound a significantly higher amount than the controls. This could represent an upregulation of the EGF receptor in response to the lack of EGF. Postnatally, the pups from EGF-immunized mothers grew faster and were on paar with controls within 1 wk. We found no differences concerning tooth eruption, ear opening, and eye opening. In extension of present knowledge concerning the tissue localization of EGF and its receptor and concerning the pharmacologic effects of EGF, our study demonstrates an effect of EGF deficiency. This supports a role for EGF in the epigenetic regulation of the development of the lungs, the skin, and the liver.

Renal uptake and excretion of epidermal growth factor from plasma in the rat.

The rat excretes around 2 nmol epidermal growth factor (EGF) in the urine per 24 h. The urinary EGF might be derived from plasma and/or might be synthesized in the kidneys. We have used the rat to study the renal uptake and excretion of homologous EGF from plasma. I.v. injected 125I-EGF was removed from the circulation within a few minutes. 5 min after the injection, the kidneys contained 12% of the 125I-EGF. The kidneys seemed to degrade most of the 125I-EGF which they accumulated from blood, as only 4% of the injected label was excreted as intact 125I-EGF in the urine. The amount of endogenous EGF in plasma was under the detection limit of our enzyme-linked immunosorbent assay (0.03 nmol/l) and it remained so after bilateral nephrectomy. Even if plasma EGF was 0.03 nmol/l excretion of EGF from plasma could account for less than 5% of the urinary EGF. This study shows that the kidneys are able to accumulate EGF from plasma and excrete a part of it as intact EGF in the urine. However, excretion of immunoreactive EGF from plasma can only account for a minor part of the urinary EGF.

Epidermal growth factor in the rat lung

SummaryEpidermal Growth Factor (EGF) in pharmacological doses is able to induce precoccious lung maturation in rabbits and sheeps. As EGF is probably acting in a para- or autocrine way, we have searched for EGF in the lungs.We report EGF immunoreactivity to be present in the type II pneumocytes of the rat from a couple of days prior to birth and throughout life. Further, we report EGF immunoreactivity to be present in cells in the bronchi and the bronchioles from day 20–21 of gestation and throughout life. G-200 gelchromatography of lung extracts indicates that the EGF-reactive material is a high molecular weight form of EGF.Since previous studies have shown that EGF in pharmacological doses is able to promote lung maturation, our results may imply a physiological role for EGF in the lungs.

Epidermal growth factor reactivity in rat milk

The concentration of EGF immunoreactivity in rat whey increases from 0.3 pmol/ml at lactation day 1 to 2.0 pmol/ml at lactation day 19. The concentration of EGF is not influenced when the rats undergo sialoadenectomy prior to mating. On S-200 gel chromatography, almost all EGF-reactivity in rat whey elutes as a broad peak corresponding to a Stokes radius of 4.0 nm (an approximate molecular weight of 80 kDa). Almost no 6 kDa EGF is present. Judged by gel filtration of whey pre-incubated with 125I-EGF (6 kDa), no binding protein for EGF is present in rat whey. When rat milk is incubated overnight at 37 degrees C, the 80 kDa EGF is degraded and elutes as a peak with a Stokes radius of 2.7 nm, corresponding to a molecular weight of approximately 35 kDa EGF and as a peak corresponding to 6 kDa EGF. Also, after partial purification by immuno-affinity chromatography, the EGF-reactive material in rat whey behaves as a peptide with a Stokes radius of 2.7 nm, corresponding to a molecular weight of approximately 35 kDa at gel filtration. Comparative binding studies between EGF purified from the submandibular glands and the EGF purified from rat whey confirm differences in the binding to antibodies raised against submandibular EGF, but not in binding to the EGF-receptor. Our results make it unlikely that EGF in rat whey is derived from the submandibular glands.

The urinary excretion of epidermal growth factor in the rat is reduced by aprotinin, a proteinase inhibitor

The present study on the rat shows that i.v. administration of the proteinase inhibitor aprotinin reduces the urinary output of immunoreactive epidermal growth factor (EGF) while the amount of immunoreactive EGF in the kidneys is increased. This indicates that the EGF-precursor in the rat kidney in vivo is processed by an aprotinin inhibitable proteinase. EGF is produced in the kidneys as a precursor with a molecular weight of approximately 130 kDa. In rat urine, nanomolar amounts of 6 kDa EGF are excreted per 24 h together with small amounts of high molecular weight forms of EGF. During i.v. administration of aprotinin the median urinary output of immunoreactive EGF is reduced to 15% of the excretion of control rats (23 pmol/2 h versus 157 pmol/2 h, P less than 0.001). Especially the excretion of 6 kDa EGF is reduced (median excretion 12 pmol/2 h versus 134 pmol/2 h, P less than 0.001). The amount of immunoreactive EGF in the kidney tissue is increased after aprotinin administration (median amount 0.11 pmol EGF/mg protein versus less than 0.04 pmol EGF/mg protein, P less than 0.001). Neither the creatinine clearance, the total urinary protein output, nor the volume of urine produced was affected by aprotinin.

An immunologic approach to induction of epidermal growth factor deficiency : induction and characterization of autoantibodies to epidermal growth factor in rats

Epidermal growth factor (EGF) in pharmacologic doses is able to induce growth and development in the fetus and the newborn. To investigate the opposite situation, the effects of insufficient amounts of EGF during development, we wanted to establish an in vivo model with a state of EGF deficiency. This was attempted by induction of autoimmunity to EGF in rats. Twenty rats were immunized with EGF. Fifteen of these developed autoantibodies against EGF, which, as judged by Scatchard analysis, had a median apparent affinity constant of 14 X 109 L/mol and a median concentration of binding sites of 20 X 10-9 mol/L. The antibodies recognized purified EGF from the submandibular glands (6 kD) and from urine (45 kD) and further native EGF in saliva and urine. The cross-reactivity toward transforming growth factor-α was below 3%. Binding of EGF by antibodies inhibited its binding to the EGF-receptor by approximately 97% in vitro. Investigation of in vivo metabolism of antibody-bound 125I-EGF confirmed these results, that is, the antibodies were able to inactivate EGF. The adult rats were unaffected by the induction and presence of autoantibodies, and the EGF-containing organs did not show any histologic signs of inflammation or tissue damage. Furthermore, as judged by immunohistochemistry, no major changes in the distribution and tissue concentration of EGF were seen in the adult rat. These results show that it is possible to induce homologous antibodies that can inhibit the binding of EGF to its receptor and further suggest that circulatory EGF is of no physiologic importance in the healthy, adult rat.

Pancreatic spasmolytic polypeptide, a potential growth factor for the intestine : neural control of secretion

We studied the effect of electrical stimulation of the vagus nerves and the effect of vasoactive intestinal polypeptide (VIP) on the secretion of pancreatic spasmolytic polypeptide (PSP) from isolated perfused porcine pancreas. We measured the concentration of PSP in the pancreatic juice and in the venous effluent by radioimmunoassay. The concentration in the pancreatic juice varied between 1 and 180 micrograms/ml, and in the venous effluent between 1 and 10 ng/ml. PSP is thus mainly an exocrine product. However, the concentrations in juice and venous effluent varied in parallel. Electrical vagus stimulation increased the output in the juice of PSP approximately 30 times. Atropine (10(-6) M) prevented the increase in PSP concentration during vagus stimulation, but only partially inhibited the output. VIP (10(-8) M) increased the output of PSP but decreased the concentration. We conclude from these results that PSP secretion is controlled by neural parasympathetic mechanisms that include both cholinergic and peptidergic pathways.

Epidermal growth factor and lung development in the offspring of the diabetic rat

Fetuses of diabetic mothers who were exposed to excessive glucose show delayed maturation. Under these conditions, altered growth factor expression or signaling may have important regulatory influences. We examined the role of epidermal growth factor (EGF) in lung development and maternal diabetes in the rat. In order to evaluate the possible role of glucose for the expression of EGF and the growth of lung tissue, we performed in vitro studies with organotypic cultures of fetal alveolar cells obtained from control rats.

Metabolism of i.v. administered 45 kDa epidermal growth factor in the rat

The 45 kDa epidermal growth factor (EGF-(45 kDa)) has been purified from rat urine. We have investigated the distribution and the processing of i.v. injected 125I-labeled EGF-(45 kDa) in the rat. 2.5 min after the i.v. injection only 12% of the label remained in the blood. Most of the label was found in the liver (54%), in the kidneys (7%) and in the skin (4%). The submandibular glands, stomach, small intestine, colon, spleen and lungs contained 1% or less of the radioactivity. Some of the 125I-EGF-(45 kDa) was processed to 125I-EGF-(6 kDa) immunoreactivity in the liver and in the kidneys. The kidneys excreted 125I-EGF-(45 kDa) in the urine, but we were not able to demonstrate 125I-EGF-(6 kDa) in urine. In conclusion, this study shows that homologous EGF-(45 kDa) is cleared from the circulation of rats within a few minutes, mainly by the liver and the kidneys. In vivo both the liver and the kidneys are able to process some of the EGF-(45 kDa) to EGF-(6 kDa) immunoreactivity.

Decreased Level of Epidermal Growth Factor in Milk from Diabetic Rats

ABSTRACT: Experimental diabetes was induced in rats with streptozocin before mating, and the influence of diabetes on epidermal growth factor (EGF) in milk and on other milk components was studied. Throughout the lactation period, a significant decrease was found both in the production of milk and in the concentration of EGF in milk from untreated diabetic rats compared with an insulin-treated diabetic group and a control group. Thus, the total output of EGF in milk from diabetic rats was considerably decreased. The concentrations of total protein and haptocorrin, a cobalamin (vitamin B12)-binding protein, and the content of fat, however, were unaltered by diabetes. Therefore, the decrease in milk EGF seemed to be selective compared with total protein in milk. The pups of diabetic dams had reduced body weights within 1 wk of lactation and reduced body lengths on d 16 of lactation compared with control pups. Furthermore, the time of eyelid opening was delayed, but no difference in the time of tooth eruption was observed. Insulin-treatment of diabetic rats restored the milk volume and the EGF concentration to values comparable to those of the controls. Pups of the insulin-treated diabetic dams were comparable to the pups of the controls. These results indicate that insulin deficiency in lactating rats causes a decrease in the lactational performance and in the EGF content of milk.