Epidermal growth factor excretion in burned rats

Evidence for epidermal growth factor (EGF) involvement in the physiological response to burns was sought from urinary levels of EGF, urea and creatinine in male rats using a standardized thermal skin injury model (25 per cent body surface) and treated with fluid resuscitation. Postmortem, the skin lesions were studied by microscopy to guarantee the absence of inflammatory complications. Statistically significant differences were observed in body weight, urea and creatinine excretion when compared to the basal values. When EGF excretion results were evaluated as raw data (expressed as ng/mg of creatinine or ng/day) compared to basal levels, no statistically significant differences were observed. However, when the results were expressed as percentage increases with respect to the basal values, a statistically significant increase was found over the first 7 days postinjury (P = 0.029).     

Epidermal growth factor and neurotensin induce microvillus hypertrophy following massive enterectomy

The compensatory hypertrophy that develops after massive enterectomy is rarely adequate to prevent the development of short bowel syndrome. Trophic hormones such as epidermal growth factor (EGF) and neurotensin (NT) may be useful in improving and accelerating this adaptive response. This study delineates the effects of NT and EGF on remnant, small bowel at the microvillus cellular level, which is the prime determinant of surface area. New Zealand white rabbits (2 kg) underwent midgut transection (sham) or 70% jejunoileal resection. Alzet pumps containing saline solution (control), EGF (1.5 μg/kg/hr), or NT (900 μg/kg/day) were implanted in resected animals after which they underwent 1 week of infusion. A second group of EGF animals was killed 2 weeks after infusion completion to assess delayed effects (EGF-delayed). Proximal jejunum was fixed for light and electron microscopy; villus and microvillus parameters were read in a blinded fashion. EGF (2.17±0.05 μm), EGF-delayed (2.26±1.5. μm, and NT (1.96±0.02 μm) animals had significantly increased microvillus heights compared to the control group (1.49±0.04 μm). Calculated brush-border surface areas were increased in a similar fashion. EGF and NT failed to elicit increases in jejunal gross villus heights. EGF and NT induce enterocyte microvillus hypertrophy and increase absorptive surface area in remanant bowel after massive enterectomy. In addition, the trophic effects of EGF persist after cessation of infusion. These peptides may be useful in accelerating small bowel adaption and preventing the development of short gut syndrome. Supported by National Institutes of Health grant 1R29DK47989-01A1 (H.C.S.). Presented in part at the Thirty-Seventh Annual Meeting of The Society for Surgery of the Alimentary Tract, San Francisco, Calif. May 19–22, 1996.     

Epidermal growth factor receptor gene analysis in renal cell carcinoma

The epidermal growth factor receptor binds the mitogens epidermal growth factor and transforming growth factor-alpha. Increased expression of the epidermal growth factor receptor has been noted in many types of tumors and is associated with gene amplification in several including epidermoid carcinoma, lung carcinoma, breast carcinoma and glioblastoma. We have recently observed increased expression of the epidermal growth factor receptor messenger RNA in neoplastic tissue relative to normal kidney tissue from patients with renal cell carcinoma. To determine if epidermal growth factor receptor gene amplification was present in renal cell carcinoma, DNA was extracted from renal cell carcinoma cell lines and from normal kidney and renal cell carcinoma tissues derived from radical nephrectomy specimens from thirty patients. DNA was analyzed by Southern blot hybridization. There was no epidermal growth factor receptor gene amplification detected in the renal cell carcinoma samples studied, indicating the increased epidermal growth factor gene expression observed in renal cell carcinoma does not occur through gene amplification. Unlike other tumors with enhanced epidermal growth factor receptor gene expression, amplification of this gene does not appear to be a common feature of renal cell carcinoma.     

Epidermal growth factor potentiates renal cell death in hydronephrotic neonatal mice, but cell survival in rats

BACKGROUND: Epidermal growth factor (EGF) markedly attenuates tubular apoptosis induced by unilateral ureteral obstruction (UUO) in the neonatal rat, and reduces apoptosis induced by mechanical stretch of cultured rat tubular cells. METHODS: To investigate the role of EGF in modulating apoptosis resulting from UUO, neonatal wild type and mutant mice lacking EGF (knockout), or with diminished EGF receptor activity (waved-2 mutant) were compared to control mice for tubular apoptosis and atrophy. Rat and mouse kidneys were compared for localization of the EGF receptor. Apoptosis was also measured in cultured mouse tubular cells subjected to stretch and exposed to EGF. RESULTS: UUO reduced endogenous renal EGF expression in wild-type mice. Unlike the rat, exogenous EGF did not decrease tubular apoptosis or atrophy in the obstructed kidney, and significantly increased stretch-induced apoptosis of cultured mouse tubular cells. Tubular apoptosis was 50% lower in the obstructed kidney of EGF knockout and waved-2 mice relative to wild type and heterozygous animals. Exogenous EGF increased tubular apoptosis and doubled atrophy in the obstructed kidney of waved-2 mice. Species differences in EGF receptor localization were detected in 3-day-old kidneys. CONCLUSION: EGF acts as a survival factor in the neonatal rat, but potentiates tubular cell death in the neonatal mouse. Species differences are maintained in cultured cells, suggesting that differences in EGF receptor signaling underlie these opposing effects.     

Epidermal growth factor suppresses renal tubular apoptosis following ureteral obstruction

Objectives. Acute unilateral ureteral obstruction (UUO) results in ipsilateral hydronephrosis characterized by a decrease in epidermal growth factor (EGF) mRNA expression and EGF protein levels in the distal renal tubules. UUO results in programmed cell death with increases in the characteristic markers of apoptosis. To suppress the apoptotic response during UUO, recombinant EGF was administered during renal obstruction and the ensuing molecular and histologic changes were studied.Methods. Mature Sprague-Dawley rats underwent left ureteral obstruction and the kidneys were harvested at 24, 48, and 72 hours. Markers of apoptosis included DNA laddering pattern on agarose gel electrophoresis, in situ gap labeling of fragmented DNA for quantitative apoptotic body determination, polyadenylated mRNA expression of SGP-2, and in situ hybridization for sulfated glycoprotein-2 (SGP-2) mRNA. Studies were repeated in rats following administration of 10, 20, and 40 μg of subcutaneous recombinant EGF on a daily basis after UUO.Results. Subcutaneous injection of EGF into unilaterally obstructed rats promotes renal tubular epithelial cell regeneration, as demonstrated by increased cortical mitotic activity. Systemic EGF supplementation in these unilaterally obstructed rats also resulted in a decrease in the intensity of the DNA laddering pattern associated with renal tubular apoptosis. An in situ labeling procedure to identify apoptotic nuclei in the ureterally obstructed kidneys revealed a 50% reduction in apoptosis after EGF administration. Northern blot analysis and in situ hybridization for SGP-2 mRNA or clusterin gene product also revealed a decreased expression in the obstructed and EGF-treated renal parenchyma.Conclusions. These data suggest that EGF, apart from its known role as a mitogenic substance for renal tubular epithelial cells, is also a critical in vivo renal cell survival factor for the developmentally mature kidney.     

Epidermal growth factor augments postpneumonectomy lung growth

OBJECTIVE: Epidermal growth factor has been shown to play an important role in prenatal and postnatal lung development, but little is known about its effects on adult lung growth. We hypothesized that postpneumonectomy compensatory lung growth can be augmented by the administration of epidermal growth factor. METHODS: Adult Sprague-Dawley rats were divided into 3 groups. Sham left thoracotomy was performed in the first group (group C), left pneumonectomy in the second group (group P), and left pneumonectomy with administration of epidermal growth factor (0.2 microgram/g body weight intraperitoneally, at 72-hour intervals) in the third group (group E). The right lung growth was studied in each group 1, 3, 5, 10, and 21 days after the operation. Lung weights (in grams) and volumes (in milliliters) were expressed as a ratio to the total body weight (in kilograms) (lung weight and volume indices). Epidermal growth factor receptor was quantitated by using Western blotting. RESULTS: Using analysis of variance and contrast analysis, we noted a significant increase in lung weight index in group E versus group P rats at 3 days (3.08 vs 2.75; P =.034) and 21 days (4.62 vs 3.61; P =.006). Lung volume index was significantly increased in group E versus group P rats at 5 (16.98 vs 15.09), 10 (24.48 vs 18.81), and 21 (28.54 vs 21.01) days (P <.001). Epidermal growth factor receptor was noted to be up-regulated in the lungs of animals that received exogenous epidermal growth factor. CONCLUSIONS: This study demonstrates that administration of exogenous epidermal growth factor has a significant effect on postpneumonectomy lung growth. This process may be mediated by an up-regulation of growth factor receptor expression in the contralateral lung.     

Modification of the epidermal growth factor response by ammonia in renal cell hypertrophy

Epidermal growth factor (EGF) causes proliferation in renal tubular cells but, when it is combined with transforming growth factor-beta1, it causes hypertrophy by a mechanism that requires the activity of the retinoblastoma family of proteins. In contrast, ammonia causes hypertrophy by decreasing lysosomal proteolysis; in some cell types, it also decreases cellular proliferation. These studies were designed to determine whether ammonia, like transforming growth factor-beta1, could convert EGF-induced hyperplasia to hypertrophy. Cultured NRK-52E cells were incubated with EGF and/or ammonia and the protein/DNA ratio was measured, as a marker of hypertrophy. Addition of ammonia to EGF-treated NRK-52E cells converted EGF-induced hyperplasia to hypertrophy, because of a decrease in DNA synthesis. The mechanism involved no change in EGF-induced protein synthesis. Inhibition of lysosomal function with a proton pump inhibitor or lysosomal protease inhibitors also converted the response of EGF-treated cells to hypertrophy. Expression of the human papilloma virus 16 E7 protein (which inactivates all members of the retinoblastoma family) prevented ammonia from converting EGF-induced hyperplasia to hypertrophy. It is concluded that ammonia converts EGF-induced hyperplasia to hypertrophy by a mechanism that involves suppression of lysosomal function and this response can be blocked by inhibiting the activity of the retinoblastoma family of proteins.     

Epidermal growth factor receptor expression in human renal allograft biopsies: an immunohistochemical study

OBJECTIVE: Epidermal growth factor receptor (EGFR) expression has been implicated in the progression of many tumors related to cell proliferation, differentiation, invasion and inhibition of apoptosis, and EGFR-targeted therapy options are under development. EGFR expression has been identified in normal and diseased native kidneys. However, its expression in renal allografts and its relation to rejection remains unclear. We aimed to investigate EGFR expression in renal allograft biopsies. MATERIAL AND METHODS: Sections from 52 renal allograft and 11 implantation biopsies were stained by EGFR antibody with streptavidin-biotin-immunoperoxidase method. Immunostaining of EGFR in renal tubules was scored semiquantitatively and the percentage of glomeruli expressing EGFR was determined. The results were correlated with Banff scores and serum creatinine values. RESULTS: Tubular EGFR expression was observed in 81.8% of implantation and 92.3% of allograft biopsies. Glomerular EGFR expression was identified in 18.2% of implantation and in 26.9% of allograft biopsies. The mean percentage (%) of glomeruli-expressing EGFR was 3.73+/-0.84 for implantation biopsies and 7.9+/-0.17 for allograft biopsies (p = 0.53, Mann Whitney U test). For implantation biopsies, tubular EGFR expression scores were 1.90+/-2.11 and for allograft biopsies, 2.89+/-2.01 (p = 0.08, Mann Whitney U test). Tubular EGFR expression was moderately correlated with interstitial fibrosis and tubular atrophy for allograft biopsies (p = 0.04, r = 0.3 and p = 0.04, r = 0.3, respectively, Spearman's rank correlation). CONCLUSIONS: These findings suggest a possible role of EGFR expression in renal scarring in the course of chronic allograft nephropathy, probably involved in a complex pathway.     

Epidermal growth factor receptors in parathyroid tumors

Hyperparathyroidism is caused by parathyroid adenomas, hyperplastic parathyroid glands, or rarely parathyroid carcinoma. Membrane receptors to epidermal growth factor (EGF), a growth-stimulating polypeptide, have been shown in other endocrine tissues such as thyroid, breast, and ovary, but not in parathyroid glands. Therefore we studied abnormal parathyroid glands from fourteen patients for the presence of EGF receptors. The binding of radioiodine-labeled EGF to the crude membrane fractions was studied using competitive inhibition with unlabeled EGF. In ten patients with solitary parathyroid adenomas, seven adenomas had no EGF binding, three had low affinity EGF binding with dissociation constants (Kd) of 28 to 148 nM and maximal specific binding (Bmax) of 285 to 1944 fmole/mg protein. In two patients with multiple adenomas, a high affinity EGF binding with Kd of 0.28 to 2.8 nM and Bmax of 6.7 to 43 fmole/mg protein was found. In one patient with hyperplastic parathyroid glands secondary to renal failure, a high affinity EGF binding with Kd of 1.7 nM and Bmax of 18 fmole/mg protein was found. In one patient with persistent hyperparathyroidism following a successful renal transplant (tertiary hyperparathyroidism), a low affinity EGF binding with Kd of 25 nM and Bmax of 219 fmole/mg protein was found. The binding of EGF did not correlate with the preoperative serum calcium or PTH levels. Thus, hyperplastic parathyroid glands (either primary or secondary) have high affinity EGF receptors whereas solitary parathyroid adenomas do not.     

Epidermal growth factor receptor in human glioma

Distribution of the epidermal growth factor (EGF) receptor in the surgical specimen of the human glioma was studied by immunohistochemical techniques using a monoclonal anti-EGF receptor antibody. Of 11 gliomas examined, EGF receptors were detected in nine glioblastomas and in one fibrillary astrocytoma. In the majority of cells, staining was observed over the cell membrane. Nuclear and cytoplasmic staining was also seen. In four glioblastomas, EGF receptor-positive cells were diffusely distributed in the tumor tissue. In one glioblastoma and one fibrillary astrocytoma, only a few positive cells were observed. These results imply the possible role of EGF receptors in the cellular proliferation of the human glioma.     

Myocardial hypertrophy in rats with renal insufficiency

Increased defatted dry wt of the heart and increased heart calcium content were observed in subtotally nephrectomized male Sprague-Dawley rats compared with sham-operated pairfed controls. Increased heart wt contrasted with no change of the weight of viscera (liver, spleen) and markedly decreased weight of striated muscle. Heart wt was unchanged after 5 days of renal insufficiency, but significantly increased after 14 or 21 days. Increased heart wt persisted despite effective beta adrenoreceptor blockade (2 X 10 mg metroprolol/kg/day i.p.) or effective alpha-1-adrenoreceptor blockade (2 X 2 mg prazosin/kg/day i.p.). Increased heart wt was also demonstrable despite normalization of basal blood pressure (intraarterial blood pressure measurement in conscious animals): blood pressure was lowered in one series with hydralazine/nadolol in drinking water (calculated to deliver 20 and 2 mg/kg/day, respectively) and in another series with furosemide in drinking water (15 mg/kg/day) combined with metoprolol (2 X 10 mg/kg/day i.p.). Increased heart wt was also noted despite correction of anemia by blood transfusion (Hct greater than 40%) and after parathyroidectomy in animals kept eucalcemic with high dietary calcium. Micromorphometry of left ventricular myocardium in perfusion-fixed tissue showed no significant change of the relative proportion of connective tissue and myocardial fibers. Myocardial isomyosin pattern was changed with an increase of fast-migrating V1 isomyosin in animals with renal insufficiency compared to sham-operated pairfed controls.     

Pentoxifylline ameliorates renal tumor necrosis factor expression, sodium retention, and renal hypertrophy in diabetic rats

BACKGROUND/AIM: Diabetic nephropathy contributes substantially to cardiovascular morbidity and mortality associated with diabetes. Urinary tumor necrosis factor (TNF) excretion is increased during diabetes and serves as an important mediator of pathological changes during the initial stages of diabetic nephropathy, including sodium retention and renal hypertrophy. We tested the hypothesis that pentoxifylline (PTF), an agent that inhibits TNF synthesis, could prevent sodium retention and renal hypertrophy during diabetes. METHODS: Proximal and distal tubule TNF expression, urinary TNF excretion, sodium retention, and renal hypertrophy were examined in control, diabetic, and PTF-treated diabetic rats. RESULTS: TNF mRNA and protein levels were increased in proximal tubule cells isolated from diabetic rats compared to control rats. In contrast, TNF expression in distal tubule cells was not increased during diabetes. PTF prevented the increase in TNF mRNA and protein in proximal tubule cells during diabetes and reduced urinary TNF excretion. PTF therapy decreased whole animal sodium retention by enhancing urinary sodium excretion in diabetic rats. In addition, PTF reduced renal hypertrophy in diabetic rats. CONCLUSIONS: The proximal tubule is an important site of TNF production during diabetes and PTF is an effective therapy for preventing the pathological changes accompanying early diabetic nephropathy.     

表皮生长因子改善移植小肠黏膜屏障功能的实验研究

目的了解表皮生长因子(epidermalgrowthfactor,EGF)对移植小肠通透性及细菌易位的作用。方法以Wistar大鼠为供体,SD大鼠为受体行异位全小肠移植,并以环孢素A(CsA,6mg.kg-1.d-1,im)抑制排斥反应。表皮生长因子组(EGF组)用微量输液泵持续均匀输入EGF200μg.kg-1.d-1;对照组输入等量生理盐水。第7天以乳果糖及甘露醇行移植肠灌注并收集尿液行高效液相色谱仪分析乳果糖及甘露醇含量,第8天采集移植肠系膜淋巴结及门静脉血行细菌培养。结果对照组尿液中乳果糖含量[(0.093±0.008)vs(0.015±0.002),P=0.0001]及乳果糖/甘露醇比值[(0.132±0.021)vs(0.020±0.005),P=0.0001]明显高于基准,EGF组乳果糖含量[(0.043±0.008)vs(0.015±0.002),P=0.0054]及乳果糖/甘露醇比值[(0.060±0.017)vs(0.020±0.005),P=0.0029]也较基准增加,EGF组乳果糖含量[(0.043±0.008)vs(0.093±0.008),P=0.0067)及乳果糖/甘露醇比值[(0.060±0.017)vs(0.132±0.021),P=0.0116]显著低于对照组。EGF组移植肠系膜淋巴结细菌阳性率为10%,对照组阳性率为60%,明显高于EGF组(P=0.028)。EGF组与对照组门静脉血培养阳性率比较差异无统计学意义(P>0.05)。结论本研究提示EGF能够降低同种移植小肠的通透性及细菌易位率,改善肠黏膜屏障功能。     

Epidermal growth factor receptor and transformation

The action of transforming growth factor peptides is mediated by distinct membrane receptors, which in turn activate a postreceptor signaling mechanism, eventually resulting in a mitogenic response. Such a signaling pathway may be modified by oncogene expression at the receptor or postreceptor levels, as well as by alterations in the levels of expression of the growth factor itself. One of the most extensively studied group of receptors is the type I epidermal growth factor receptor family. Activation of this receptor triggers the induction of receptor dimerization, which enables cross-phosphorylation to occur between two receptor molecules. This dimerization model provides a universal mechanism to activate the type I receptor family for growth factors and subsequent transformation. Received: May 17, 2001 / Accepted: January 8, 2002