prepro-EGF mRNA Research Articles

Compensatory Renal Growth in Uninephrectomized Immature Rats: Proliferative Activity and Epidermal Growth Factor

Compensatory response to uninephrectomy in immature animals is stronger compared with that in adult ones and the response is due mainly to renal cell proliferation. The present study explored to show the growth pattern of the remaining kidney immediately after uninephrectomy in immature rats with special reference to proliferating activity and epidermal growth factor (EGF). Immunolocalizations of proliferating cell nuclear antigen (PCNA) and EGF in immature rat kidney were examined during the first three days after uninephrectomy. Semi-quantitative analysis of the expression of preproEGF mRNA was performed. One day after the operation, the PCNA positive cell ratios in the glomeruli and the proximal tubules were significantly higher in unilaterally nephrectomized (UNx) rats than in sham-operated (Sham) rats. In UNx and Sham rats, the proximal and distal tubular cells showed positive reactions to EGF antibody. The positive reaction of proximal tubules to EGF antibody was weaker in UNx than in Sham rats 1 day after the operation, while the degree of reactivity was not different between UNx and Sham rats 3 days after the operation. The level of expression of preproEGF mRNA in the kidney was significantly lower in UNx than in Sham rats 1 day after the operation. These results indicate that unilateral nephrectomy in immature rats causes increased proliferative activity and decreased expression of EGF in the remaining kidney during the early period of compensatory renal growth.

BLADDER EPITHELIAL CELLS FROM PATIENTS WITH INTERSTITIAL CYSTITIS PRODUCE AN INHIBITOR OF HEPARIN-BINDING EPIDERMAL GROWTH FACTOR-LIKE GROWTH FACTOR PRODUCTION

The etiology of interstitial cystitis is unknown. We previously identified an interstitial cystitis urine factor, antiproliferative factor, that inhibits proliferation of bladder epithelial cells in vitro and complex changes in epithelial growth factor levels, including profound decreases in heparin-binding epidermal growth factor-like growth factor (HB-EGF). Bladder and renal pelvic catheterization of patients with interstitial cystitis indicated that the antiproliferative factor is made and/or activated in the distal ureter or bladder. Therefore, we determined whether bladder epithelial cells from interstitial cystitis cases produced the antiproliferative factor and whether purified antiproliferative factor could alter production of growth factors known to be abnormal in interstitial cystitis. Antiproliferative factor activity was determined by 3H-thymidine incorporation into primary bladder epithelial cells. The antiproliferative factor was purified by size fractionation followed by sequential chromatography involving ion exchange, hydrophobic interaction and high performance liquid chromatography. HB-EGF, epidermal growth factor, insulin-like growth factor and insulin-like growth factor binding protein 3 levels were determined by enzyme-linked immunosorbent assay. Bladder epithelial cells from patients with interstitial cystitis produced a single antiproliferative factor with the same purification profile as that purified from interstitial cystitis urine. Purified antiproliferative factor specifically inhibited HB-EGF production by bladder epithelial cells in vitro, and the effect of interstitial cystitis urine or purified antiproliferative factor on bladder cell proliferation was inhibited by recombinant human HB-EGF in a dose dependent manner. Similar to urine HB-EGF, serum HB-EGF was also significantly lower in interstitial cystitis cases than in controls. Bladder epithelial abnormalities in interstitial cystitis may be caused by a negative autocrine growth factor that inhibits cell proliferation by down-regulating HB-EGF production. Furthermore, decreased levels of urine and serum HB-EGF indicate that interstitial cystitis may be a urinary tract manifestation of a systemic disorder.

Epidermal growth factor stimulates the cell growth of the PA-1 teratocarcinoma cell line in an autocrine/paracrine fashion

In order to investigate the biological significance of epidermal growth factor (EGF) in the cell function of teratocarcinoma cells, we examined the production, binding and cell proliferative effect of EGF in PA-1 human ovarian teratocarcinoma cell line. The immunoreactivity of EGF in PA-1 cell-conditioned medium was detected by human EGF radioimmunoassay, and prepro-EGF mRNA was demonstrated in PA-1 cells by Northern blot analysis. An [125I]EGF binding study showed the presence of EGF receptor with very high binding affinity and relatively low numbers of binding sites in PA-1 cells. Furthermore, the growth of PA-1 cells was stimulated by EGF and inhibited by anti-EGF monoclonal antibody. These results suggest strongly that EGF plays an important role in controlling the growth of teratocarcinoma cells as an autocrine/paracrine growth factor.

Regulation of human decidual function by epidermal growth factor.

In order to clarify a regulatory mechanism of epidermal growth factor (EGF) in the decidualization process, EGF gene expression, the change in EGF receptor, and the cell proliferative effect of EGF in the human endometrium/decidua were assessed in both in vivo and in vitro decidualization systems. Northern blot hybridization showed that, although no hybridized band was found in the proliferative and secretory phase endometria, a specific band of 5 kb was detected in decidua of early pregnancy as well as in in vitro medroxyprogesterone acetate-induced decidual cells. In situ hybridization revealed that prepro-EGF mRNA was observed in the stromal cells of decidua. Scatchard plot analysis of 125I-EGF-binding studies for the homogenates from these endometria/decidua revealed that its binding sites increased in accordance with the decidualization process, and its dissociation constant remained unchanged. EGF had a stimulatory action on cell proliferation in the early pregnant decidual cells. These results demonstrate that EGF production, EGF receptor, and decidual cell growth increase in accordance with the process of decidualization, suggesting that EGF may play an important role in the regulation of decidualization in human endometrium through an autocrine/paracrine system.

Expression and distribution of epidermal growth factor in acute and chronic renal allograft rejection

Epidermal growth factor (EGF) is a fibrogenic cytokine with a possible role in chronic damage. EGF is also involved in tubular regenerative response to injury. This study investigates the expression and distribution of EGF in a rat model of renal allograft rejection. EGF was localised in control kidneys to distal convoluted tubules (DCT) and thick ascending loop of Henle (TAL). Five days post-transplantation EGF was diffusely distributed. In chronic rejection at one, three and six months, damaged areas of allografts demonstrated faint diffuse EGF staining, while well-preserved areas exhibited the normal distribution pattern. PreproEGF mRNA was significantly reduced (P < 0.01) in acute rejection and in chronic rejection at three months to 28% and 51% of normal, respectively. At six months values ranged from 16% to 166% of normal kidneys, and were inversely correlated with tubular damage (P < 0.01). PreproEGF mRNA was localized to DCT and TAL in controls and in well preserved areas of the tissue in chronic rejection. Thus, EGF would not appear to contribute to the development of injury in chronic renal rejection. It may instead exert a protective effect on tubular structures.

Impaired epidermal growth factor production in genetically obese ob/ob mice.

Epidermal growth factor (EGF) is a potent inhibitor of adipose differentiation in vitro and delays adipose tissue development in vivo. Here we show that in the homozygous male obese mice the level of EGF in the submaxillary gland and plasma is significantly lower than in the glands and plasma of age-matched control littermates. This EGF deficiency in ob/ob mice was observed as early as 5 wk of age when obesity had just become apparent and was also found in adult mice. The level of prepro-EGF mRNA expression in the submaxillary gland was also lower in obese mice than in control littermates. However, the level of kidney prepro-EGF mRNA was the same in mice with both phenotypes, suggesting that the regulation of prepro-EGF mRNA expression is different in both tissues. These results indicate that genetic obesity in mice is accompanied by a decrease in the production of EGF.

Comparison between epidermal growth factor, transforming growth factor-α and EGF receptor levels in regions of adult rat brain

Examination of adult rat brain regions by specific radioimmunoassays revealed a widespread distribution of transforming growth factor-α (TGF-α), but not epidermal growth factor (EGF), the peptide that had previously been reported to be present in rodent brain. Polyadenylated RNA samples from the different regions of rat brain were analyzed by Northern blot to identify mRNA species encoding precursor proteins for EGF (preproEGF), TGF-α (preproTGF-α), and the EGF/TGF-α receptor. The results indicate that TGF-α is the most abundant ligand for the EGF/TGF-α receptor in most parts of the brain analyzed. Message for preproEGF was only detectable after prolonged autoradiographic exposure; levels of preproEGF mRNA were between two and three orders of magnitude lower in brain than those expressed in control tissue (kidney), and one to two orders of magnitude lower than preproTGF-α mRNA levels in all brain regions. These results were confirmed by analysis of mRNA by RT/PCR, and support the hypothesis that expression of preproEGF mRNA in the brain is limited to smaller discrete areas, whereas preproTGF-α gene expression is almost ubiquitous.

Ureteral obstruction decreases renal prepro-epidermal growth factor and Tamm-Horsfall expression

Northern and dot-blot analysis of polyadenylated RNAs of kidney cortical and outer medullary tissue was performed in male Sprague-Dawley rats at varying times up to 24 hours after bilateral ureteral obstruction (BUO), after 24 hours of unilateral obstruction (UUO) and at varying periods after release of BUO or UUO. Pre-proEGF (preproEGF) and Tamm-Horsfall (TH) mRNA declined by four hours of BUO to virtually undetectable levels at 24 hours of ureteral obstruction. Upon release of BUO or UUO, preproEGF and TH mRNA returned slowly toward normal but remained below control levels up to four days after release of ureteral obstruction. Urinary EGF excretion paralleled these changes in renal preproEGF mRNA. Although these changes are similar to those observed during nephrotoxic and ischemic renal failure, where the expression of the immediate early genes precedes the fall in preproEGF and TH expression, no such increase in the expression of these genes occurred after bilateral ureteral obstruction. These changes in preproEGF and TH expression could also be dissociated from uremia and high rates of DNA synthesis, suggesting that ureteral obstruction itself is a sufficient cause of the reduced expression. The increase in ureteral pressure and its functional and humoral effects may each play a role in reduced preproEGF and TH expression during ureteral obstruction.

Lactogenic hormones increase epidermal growth factor messenger RNA content of mouse mammary glands

Epidermal growth factor (EGF) is known to stimulate mammary epithelial proliferation, has been identified in milk and is expressed in lactating mammary epithelia. This study examined hormonal control of EGF mRNA in mammary glands of mice. Prepro-EGF mRNA (4.7 kb) was detected during lactation (and increased significantly during this period), whereas a smaller EGF-like RNA (.5 kb) was at highest levels in mammary glands of virgin and pregnant mice. The 4.7 kb RNA was polyadenylated, whereas .5 kb RNA was not. In mammary gland organ cultures from steroid-primed mice, the combinations of insulin+hydrocortisone and insulin+prolactin+hydrocortisone increased both prepro-EGF and β-casein mRNA expression. When hydrocortisone was present there was a decrease in mammary gland content of EGF-like RNA (.5 kb band). We conclude that prepro-EGF mRNA expression in mouse mammary tissue is under the control of the lactogenic hormones prolactin and hydrocortisone.

Potential Physiologic Roles for Epidermal Growth Factor in the Kidney

Epidermal growth factor (EGF) is a 53-amino acid polypeptide that is known to produce a number of biologic effects both in vitro and in vivo. High concentrations of EGF are found in urine, and high concentrations of prepro-EGF mRNA have been detected in kidney, localized to thick ascending limb of Henle (TALH) and distal convoluted tubule. Specific high-affinity EGF receptors have been demonstrated in mesangial cells, proximal tubule, and cortical and inner medullary collecting duct, as well as in medullary interstitial cells. In the proximal tubule, EGF binding and EGF receptor-associated tyrosine kinase activity are localized to basolateral membrane, and functional responses in collecting duct are observed only with basolateral administration of EGF. A number of renal responses to administration of EGF have recently been described, including modulation of glomerular hemodynamics, renal metabolism, tubular transport functions, and eicosanoid synthesis. In addition, EGF has been shown to be a potent mitogen in vitro for a variety of cell types in the kidney and may be an important mediator of renal repair following injury.

Thyroxine Increases Epidermal Growth Factor Levels in the Mouse Thyroidin Vivo*

Immunoreactive epidermal growth factor (EGF) has been detected in the thyroid, which raises questions concerning the source of thyroidal EGF and what affects its levels. We therefore have examined the effects of manipulating thyroid function on the immunoreactive EGF levels in plasma, thyroid, submaxillary gland (SMG), and kidney of adult male BALB/c mice, and we also analyzed the prepro-EGF messenger RNA in these tissues. Groups of six mice received daily injection of T4 (1 microgram, 5 micrograms, or 25 micrograms) or bovine TSH (1 mU) for up to 14 days. The plasma EGF concentration was 0.31 +/- 0.01 ng/ml in control animals, and T4 (5 micrograms) decreased the plasma levels by about one-half within 1 week. The thyroidal EGF was 0.50 +/- 0.14 ng/mg protein in control animals, and T4 (5 micrograms) increased the thyroidal EGF 8-fold within 1 week. There was a negative correlation between plasma and thyroidal EGF concentration (r = -0.93, P less than 0.01). Increasing doses of T4 also increased the SMG EGF content, while plasma levels fell (r = -0.88, P less than 0.01). The TSH treatment did not significantly alter the plasma or tissue EGF levels. Studies on mRNA prepared from these three tissues, using the reverse transcription and the polymerase chain reaction, indicated that the prepro-EGF mRNA was present in thyroid, SMG, and kidney. In conclusion, it appears that at least some thyroidal EGF is synthesized in the thyroid. Our observations that T4 increases the level of intrathyroidal EGF in a dose- and time-dependent fashion, while plasma levels fall, suggest the possibility that intrathyroidal EGF represents a shortloop feedback for the autocrine and/or paracrine regulation of thyroid function.

Changes in gene expression after temporary renal ischemia

Temporary renal ischemia is followed by increased DNA synthesis and cell division as the kidney restores the continuity of the renal epithelium. We sought to characterize some of the changes in proto-oncogene and growth factor expression during this proliferative response. Northern analysis of polyadenylated RNAs of kidney cortical and outer stripe of outer medullary tissue from male Sprague-Dawley rats was performed following release of renal hilar clamping of 50 minutes duration. Ischemia produced an increase in c-fos mRNA that reached a peak at one hour and declined rapidly to control levels by four hours after release of the clamp. A similar rapid increase and decrease in early growth response 1 (Egr 1) mRNA was noted. The response of these immediate early genes was typical of their response to mitogens, suggesting that they served a similar role in renal cell regeneration. Levels of c-Ki-ras and glyceraldehyde phosphate dehydrogenase mRNA were unchanged. Renal preproEGF mRNA decreased at two hours, was virtually absent by 24 hours and remained low for at least four days after ischemia. Urinary excretion of EGF fell immediately after release of ischemia and before the decline in preproEGF mRNA or SNGFR, suggesting post-transcriptional affects of ischemia on renal EGF production. EGF excretion returned to only 50% of control by day 21. Specific 125I-EGF binding increased in membrane fractions of cortex, outer medulla and inner medulla as early as 24 hours after release of the clamp. Cortical 125I-EGF binding increased in the proximal tubule but not in the glomerulus.(ABSTRACT TRUNCATED AT 250 WORDS)

Defective epidermal growth factor gene expression in mice with polycystic kidney disease

The C57BL/6J- cpk mouse has an inheritable form of polycystic kidney disease similar to the autosomal recessive disorder seen in humans. Between approximately 1 and 3 weeks of age, affected cpk mice develop numerous large cysts in the collecting tubule segment of kidney nephrons. The present study examined the ontogeny of renal and submandibular gland prepro-epidermal growth factor (preproEGF) gene expression in the cpk mouse using Northern blot hybridization and immunohistochemistry. There was a virtual absence of renal preproEGF gene expression in cystic kidneys over the 3-week postnatal period, during which time renal preproEGF mRNA and proEGF/EGF protein normally reach significant levels. PreproEGF mRNA was expressed in salivary glands of cystic mice; however, this mRNA could not be further elevated with testosterone suggesting that there are abnormalities in the regulation of the preproEGF gene in the submandibular gland, as well as in the kidney. Since renal preproEGF expression during the early postnatal period occurs when collecting duct cysts form, it is possible that a deficiency in renal proEGF or EGF contributes to the rapid development of collecting duct cysts and the concomitant renal failure in the C57BL/6J- cpk cystic mouse.

Estrogen Regulates the Synthesis of Epidermal Growth Factor in Mouse Uterine Epithelial Cells

Immunocytochemical analyses, using several mouse epidermal growth factor (EGF) polyclonal antibodies, detected immunoreactivity only in uterine luminal and glandular epithelia on late proestrus, estrus, and early on day 1 of pregnancy, but not late on day 1. This immunoreactivity was not detected in the ovariectomized uterus, but after estrogen stimulation it was detected first in the luminal epithelium between 12-24 h and then also in the glandular epithelium by 48 h. After 72 h of estrogen withdrawal, EGF immunoreactivity was no longer detected. This response was specific for estrogen and did not occur after progesterone injection (2 mg/day for 4 days). Using antipeptide antibodies specific for prepro-EGF, no immunoreactivity was detected in the ovariectomized uterus, weak reactivity was detected in the estrogenized uterus and submandibular gland, and strong reactivity was detected in the kidney. Northern blot analysis of uterine RNA failed to detect the expected 4.8-kilobase prepro-EGF mRNA, but, instead, a rare transcript of 2.4 kilobases was detected, which suggests that EGF mRNA is alternately processed in the uterus. The presence of an EGF-coding uterine transcript was further documented by hybridization of an EGF-coding region-specific oligodeoxyribonucleotide (oligo) to polymerase chain reaction-amplified uterine cDNA. In situ hybridization, using a prepro-EGF cRNA probe as well as an EGF-coding region-specific oligo, showed hybridization that colocalized with the EGF immunostaining (epithelia) and was absent from non-EGF-immunoreactive cells. Pulse labeling experiments coupled with immunoaffinity chromatography showed that estrogen induced an increase in the relative rate of synthesis of an acid-soluble immunoreactive protein which was the same size as authentic EGF. Furthermore, analysis of acid-soluble uterine proteins fractionated by DEAE-cellulose chromatography demonstrated a single coincident peak of antigenic activity and receptor-binding activity which coeluted from the column with authentic EGF. Electron microscopy localized EGF immunoreactivity to the Golgi of luminal epithelial cells. Taken together these results suggest that estrogen regulates expression of the EGF gene specifically in uterine epithelial cells. Increased expression of this gene results in an increase in the relative rate of synthesis of this protein and the accumulation of mature EGF.

Expression of the epidermal growth factor gene in mouse lachrymal gland: comparison with that in the submandibular gland and kidney

Expression of the epidermal growth factor (EGF) gene in mouse lachrymal gland was studied. The lachrymal gland of adult male and female mice contained immunoreactive EGF at a concentration of 0.013 +/- 0.002 (S.E.M.) and 0.014 +/- 0.003 ng/mg wet tissue respectively. Northern blot analysis of RNA from the lachrymal gland revealed the presence of 4.1-4.3 kb preproEGF mRNA, which was smaller in size than the 4.7-4.8 kb preproEGF mRNA in the submandibular gland and kidney. There was no sex difference in the mRNA level in the lachrymal gland, whereas the mRNA levels in the submandibular gland and kidney of adult male mice were 42-fold higher and twofold lower respectively than those of female animals. Administration of testosterone propionate or L-thyroxine to female mice increased submandibular gland levels of preproEGF mRNA by 35-fold or 12-fold respectively, but caused no change in lachrymal gland levels of preproEGF mRNA. The level of mRNA in the kidney was decreased by administration of androgen to one-third of that in control animals. The mRNA in the lachrymal gland was detected as early as 2 weeks of age and thereafter it remained at a constant level throughout adulthood, while that in the submandibular gland increased greatly during the pubertal stage. These results indicate differential hormonal and developmental regulation of EGF gene expression in the lachrymal gland, submandibular gland and kidney.

Epidermal growth factor in serum, urine, submandibular glands and kidneys of diabetic mice

Levels of epidermal growth factor (EGF) in serum were significantly decreased in streptozotocin (STZ)-diabetic mice (446±168 pg/ml) after 1 week and 423±52 after 4 weeks vs 766±162 pg/ml in controls, P.002 and < .001. respectively) and in genetically diabetic ob/ob mice (455±285 vs 962±453 pg/ml in nondiabetic ob/+ controls, P.043). The urinary excretion of EGF was significantly increased in STZ mice (104±53 vs 51±23 ng/h, P.013) but unchanged in ob/ob mice (33±9 vs 45±16 ng/h, P.134). However, when expressed per mg creatinine it was decreased in both cases: in STZ mice to 680±250 ng/mg at 1 week and 684±211 at 4 weeks vs 1250±303 ng/mg in controls (P<.01); and in the ob/ob mice to 552±117 vs 1237±300 ng/mg in ob/+ controls (P<.01). EGF content of the submandibular glands of STZ mice remained unchanged at 1 week (13.1±2.9 vs 11.0±1.8 μg/mg protein, P. 170) but dropped by 4 weeks (4.7±1.2 μg/mg, P<.001); in the ob/ob mice it was less than 20% that of controls (2.1±0.8 vs 12.2±3.6 μg/mg protein). In kidneys, the EGF content was not altered in either ob/ob (524±50 vs 571±33 pg/mg protein) or STZ mice (652±183 vs 665±80 pg/mg). The preproEGF mRNA level in STZ-treated mice was reduced after 4 weeks in submandibular glands but not in kidneys. The results show that diabetes affects EGF production, utilization and/or excretion in mice and that kidneys are spared from suppressionof EGF synthesis that is pronounced in the submandibular glands.

Reduced renal prepro-epidermal growth factor mRNA and decreased EGF excretion in ARF

Levels of prepro epidermal growth factor (EGF) mRNA in renal cortical tissue and urinary EGF excretion have been determined during cisplatin and ischemia-induced acute renal failure in the rat. Northern analysis of polyadenylated RNAs of kidney cortical tissue showed diminished renal preproEGF mRNA in rats injected with cisplatin (5 mg/kg). The decrease in preproEGF mRNA occurred as early as 12 hours in the kidney and persisted for at least three days after cisplatin injection. The submandibular gland, a major site of EGF synthesis, contained normal levels of preproEGF mRNA. Transplatin, a non-nephrotoxic isomer of cisplatin, did not reduce renal preproEGF mRNA levels. Northern analysis of polyadenylated RNAs of kidney cortical tissue 24 hours after a 50 minute period of renal pedicle clamping also showed reduced preproEGF mRNA levels. By contrast, cisplatin increased renal c-fos mRNA. Urinary EGF excretion was also reduced after cisplatin and ischemia and the decrease in EGF excretion correlated significantly with the degree of renal failure. The data show that nephrotoxic and ischemic renal cell injury reduces preproEGF mRNA and urinary EGF excretion. Reduced preproEGF mRNA and diminished EGF excretion may be important in the functional and regenerative responses to renal injury.

Epidermal growth factor deficiency associated with diabetes mellitus.

The production of epidermal growth factor (EGF) in the submandibular gland and its circulating level were studied in diabetic mice. In genetically diabetic (C57BL/KsJ db/db) mice, EGF concentrations in the submandibular gland and plasma were reduced to 13% and 30% of the control levels, respectively. In streptozotocin-treated diabetic mice, they were reduced to 18% and 20% of controls, respectively, 5 weeks after the drug injection. Furthermore, levels of submandibular prepro-EGF mRNA in these diabetic mice were decreased almost in parallel with the glandular EGF concentrations, while there was no change in the levels of submandibular beta-actin mRNA and kidney prepro-EGF mRNA. In addition, histological examination of the submandibular glands indicated that the size of the granular convoluted tubules, which produce EGF, was substantially reduced in the diabetic mice. Insulin administration to streptozotocin-treated mice almost completely reversed the decrease in EGF content in the submandibular gland, substantially elevated the level of the glandular prepro-EGF mRNA and plasma EGF concentration, and increased the size of the granular convoluted tubules in the gland. These results indicate that EGF deficiency occurs in diabetes mellitus and that insulin may be important in maintaining the normal level of EGF in the submandibular gland and plasma.

Epidermal Growth Factor Precursor in Mouse Lactating Mammary Gland Alveolar Cells

Previous studies have demonstrated that high levels of epidermal growth factor (EGF) occur in human and rodent milk and that oral administration of this polypeptide stimulates rodent gastrointestinal development. It is not known whether EGF in milk originates from cells of the lactating mammary gland or is sequestered from an extramammary source. In the present study, prepro-EGF mRNA (approximately 4.7 kilobases) was detected in the CD-1 mouse mammary gland throughout the period of lactation; by comparison, negligible levels of this EGF transcript were found in the gland during pregnancy. Low levels of EGF immunoreactivity (4-5 ng/g wet wt tissue) were extracted from lactating (day 18) mammary glands with dilute acetic acid. Immunolocalization was evident with antisera to either EGF or two other regions of the EGF precursor in essentially all alveolar cells of the lactating gland. The most prominent staining with antiserum to EGF was observed along the luminal borders of cells; this pattern of cellular staining required proteolytic pretreatment of tissue sections. Western blot analyses of cell membranes isolated from the day 16 lactating mammary gland revealed an EGF-immunoreactive band at about 145K, which was equivalent in size to the EGF precursor found in mouse kidney cell membranes. Despite these findings, labeling of lactating mammary gland mince with L-[35S]methionine and cysteine for up to 4 h did not reveal any specific bands in immunoprecipitates. These cumulative findings suggest that the precursor form of EGF occurs in alveolar cells of lactating mammary gland and that this protein is translocated to the cell membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

The regulation by thyroid hormones and androgen of epidermal growth factor synthesis in the submandibular gland and its plasma concentrations in mice

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.