Concentrations Of TGF-alpha Research Articles

Regulation of plasminogen activator activity in transitional carcinoma cell lines by wound site growth factors.

The effect of two growth factors ellicited in response to surgical woundings (transforming growth factor alpha [TGF alpha] and beta 1) on the regulation of cellular plasminogen activator activity (PAA) in human transitional carcinoma cell lines, with differing baseline PAA (253J--high; 647V--low), was studied. mRNA transcript levels of PA regulatory proteins in both cell lines were responsive to TGF alpha and TGF beta 1. However, both the magnitude and nature of the response differed markedly between the two lines. TGF alpha increased uPA transcript levels in both cell lines in a dose-dependent fashion. In the case of uPA receptor, exogenous TGF alpha concentrations which increased receptor levels over fivefold in the 253J line had no effect on this transcript in the 647V line. This differential responsiveness was even more pronounced for TGF beta 1. TGF beta 1 appeared to increase uPA transcript in the 253J line in a dose dependent manner while decreasing transcript levels in the 647V line. uPAr mRNA in 253J cells increased over a 19-fold range in response to TGF beta 1 while this same transcript was decreased 14-fold in 647V cells. The most pronounced effect of TGF beta 1 was seen on PAI1 transcript levels in the 253J line. This transcript increased in a concentration dependent fashion from non-detectable levels. These findings demonstrate that growth factors ellicited by surgical wounding may alter the biology of neoplastic cells. Both the growth factor milieu, and intrinsic cellular regulatory mechanism, appear important in determing net PAA in transitional carcinoma cell lines.

Elevated serum levels of transforming growth factor-alpha in breast cancer patients.

Previous studies suggest that transforming growth factor-alpha (TGF alpha) may have the potential of a tumor marker. Since the levels of serum TGF alpha in cancer patients and healthy individuals have not been reported, we determined the serum TGF alpha levels of 83 breast cancer patients and 74 healthy individuals by using a TGF alpha radioimmunoassay kit. All of the cancer patients' sera were positive for TGF alpha; their TGF alpha concentrations ranged from 210 to 740 pg/ml, with a mean of 353 +/- 98 pg/ml. Sixty-seven percent (50 cases) of normal sera were positive for TGF alpha; the levels ranged from 120 to 207 pg/ml, with a mean of 144 +/- 17 pg/ml. The difference in serum TGF alpha levels between cancer patients of different disease stages and healthy individuals was found to be statistically significant by Student t-test and the Mann-Whitney test. No correlation was found between serum carcinoembryonic antigen and TGF alpha levels. The potential of serum immunoreactive TGF alpha as a marker for breast cancer warrants further investigation.

Effect of Chronic Insulin Administration on Mouse Parotid and Submandibular Gland Function

Chronic (six-day) injection of insulin (im, 50 microM/animal) into BALB/c mice resulted in changes in secretory function, hypertrophy and hyperplasia of the parotid and submandibular glands. There were no significant changes in the flow rate or concentrations of proline-rich proteins, TGF alpha, or amylase in saliva when measured against constant protein levels. However, amylase enzyme activity and total saliva protein content were reduced when measured against constant saliva volume. In contrast, EGF synthesis and secretion from the submandibular gland was increased. Both the parotid and submandibular gland showed evidence of gland hypertrophy and increased rates of DNA synthesis as indicated by [3H]-thymidine incorporation in response to insulin treatment. Chronic injection of insulin did not effect the level of receptor in the plasma membrane of either gland.

TGF-alpha can act as morphogen and/or mitogen in a colon-cancer cell line.

Transforming growth factor alpha (TGF-alpha) has multifunctional biological effects on a variety of mesenchymal and epithelial cells. It is a potent mitogen for a number of normal and transformed cell types, regulates extracellular matrix (ECM) production and promotes breast, kidney and lung morphogenesis. To clarify the role of ECM proteins in the morphogenetic and mitogenic effects of TGF-alpha, we have used a human colon carcinoma cell line (SW1222) which expresses EGF receptor. Here we show that TGF-alpha at 1 ng/ml increases the proliferation of SW1222 cells, but only when they are cultured on plastic rather than collagen-coated plates. Higher concentrations of TGF-alpha (10 ng/ml) did not increase cell proliferation but significantly enhanced the crypt-like glandular differentiation when cells were grown in 3-dimensional collagen gel (p = 0.027). These effects were accompanied by increased expression of alpha 2 beta 1 and alpha 3 beta 1 integrin molecules, which are receptors for extracellular matrix proteins, and by a statistically significant increase in binding of SW1222 cells to type-1 collagen. The effects of TGF-alpha both on binding to type-1 collagen and on morphological differentiation in 3-dimensional collagen gel were inhibited by monoclonal antibodies recognizing the alpha 2 beta 1 integrin. These data indicate that the morphogenetic or mitogenic activities of TGF-alpha are critically dependent on cellular interactions with extracellular matrix proteins and are primarily mediated by the alpha 2 beta 1 integrin receptor. Inappropriate expression of this growth factor, seen in tumours whose cell-matrix interactions are greatly impaired, could have deleterious effects on the maintenance of normal tissue architecture and growth control.

Characterization of the synthesis and secretion of transforming growth factor-alpha from salivary glands and saliva.

Whole saliva collected from rat, mouse, and human sources was found to contain high concentrations of transforming growth factor-alpha (TGF alpha) when analyzed by RIA. The concentrations of TGF alpha in unstimulated human saliva (age, 30-45 yr; n = 10; 1.5 +/- 3.1 nM) was reduced with age (age, 55-70 yr; n = 10; 0.4 +/- 0.1 nM), but increased in oral pathologies manifested in xerostomia (age, 57-70; n = 6; 0.8 +/- 0.2 nM) and Paget's disease (age, 58-76; n = 8; 2.0 +/- 0.6 nM). Immunohistochemical localization of TGF alpha in the salivary glands of rats and mice revealed specific immunostaining of the granular ductal cells of the parotid and submandibular glands. Reverse transcription followed by polymerase chain reaction amplification of total RNA from the parotid and submandibular glands of rats and mice demonstrated the presence of TGF alpha mRNA, suggesting endogenous synthesis by the salivary glands. Thus, salivary glands appear to be an exocrine source for a second member of the epidermal growth factor-like growth factor family in the oral cavity.

Epidermal growth factor, transforming growth factor-alpha, and epidermal growth factor receptor content in normal and carcinomatous gastric and colonic tissue.

Epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) are polypeptides which bind to the EGF receptor (EGFr) and may play a role in cell growth and carcinogenesis. Our study investigated the content of EGF, TGF-alpha, and EGFr in tumors of the stomach and the colon in comparison with the surrounding mucosa. EGF was detected in half of the stomach specimens with concentrations between 1 and 9 ng/g weight irrespective of histology. In the colon no EGF was found in the tumor or normal mucosa. In the stomach normal mucosa contained higher TGF-alpha concentrations (mean 22.4 ng/g) than the tumors (mean 11.8 ng/g), but the difference was not statistically significant because of a wide variation in mucosal values. By contrast, the colon mucosa displayed significantly higher TGF-alpha concentrations than the tumor tissues (33 ng/g versus 12 ng/g; P < 0.01). EGFr content in the gastric mucosa was lower compared to gastric carcinoma (48 fmol/g versus 75 fmol/g) yet not significantly different. In contrast, colorectal tumor specimens disclosed significantly higher concentrations than the mucosal tissues (mean of 155 fmol/g versus 80 fmol/g; P < 0.01). In conclusion, TGF-alpha should not be considered a tumorigenic but a physiological growth factor in the stomach and colon. An elevated EGFr content in colorectal tumors in comparison with the normal mucosa could lead to a growth advantage by an autostimulating mechanism.

Transforming growth factor-alpha (TGF alpha) concentrations increase in regenerating rat liver: evidence for a delayed accumulation of mature TGF alpha.

Changes in the concentration of transforming growth factor-alpha (TGF alpha) protein were measured in regenerating liver. TGF alpha stimulates both DNA and protein synthesis in various liver-derived cells, and its mRNA levels increase in liver after partial hepatectomy (PH), suggesting that it may be an important autocrine regulator of liver regeneration. Using a sheep antiserum raised against mature rat TGF alpha, we developed a sensitive TGF alpha RIA. TGF alpha was extracted from livers in a detergent-containing buffer with protease inhibitors. Liver extracts, to a volume of 10 microliters/tube, produced a displacement curve of [125I]TGF alpha that was parallel to the pure standard. The TGF alpha content of normal liver was 57.04 +/- 26.25 pg/mg protein, 5.24 +/- 2.61 ng/mg DNA, and 10.33 +/- 4.47 ng/g liver (n = 5; mean +/- SD). Between 13-17 h after operation, TGF alpha concentrations in the livers of PH animals increased over those in sham-operated (SH) controls (P < 0.05) and remained twice those in SH controls for more than 96 h, returning to control values by 8 days. In unoperated liver, gel chromatography showed all TGF alpha immunoactivity to be in fractions corresponding to known TGF alpha precursors (15-30 kilodaltons). Mature 5.6-kilodalton TGF alpha was not detected until 48 h after PH and was still present at 96 h. These data support a role for TGF alpha in the response to PH in the rat. However, the presence of TGF alpha precursors in normal liver, the short (< 4-h) interval between the increase in TGF alpha concentrations and the onset of hepatocyte DNA synthesis, the sustained elevation of TGF alpha levels after DNA synthesis has ceased, and the lack of detectable processing to the mature form until DNA synthesis has subsided all suggest that the membrane-anchored precursor and the mature forms of TGF alpha may have different functions, cellular sources, or target cells in regenerating liver.

Pretreatment with vitamin A inhibits transforming growth factor alpha stimulation of human mammary carcinoma cells.

Vitamin A or retinol is an important agent in the normal differentiation and growth of cells. Retinol is an effective inhibitor of the growth of many transformed cells in vitro and in vivo but its mechanism of action is unclear. Transforming growth factor alpha (TGF alpha) is a known mitogen. We examined the effect of retinol treatment on TGF alpha stimulation of two human mammary carcinoma cell lines, one which is growth inhibited by retinol and one which is not. Pretreatment of both cell lines for 48 hours with retinol resulted in inhibition of TGF alpha stimulation of growth. In the T47D cell line the mechanism was not related to an effect on the cellular content of TGF alpha, epidermal growth factor (EGF) receptor protein, EGF receptor mRNA, or on the binding of TGF alpha to the EGF receptor. However, TGF alpha-induced stimulation of the EGF receptor substrate, phospholipase C-gamma 1, was abrogated in the T47D cell line with retinol pretreatment. In the MDA-MB-468 cell line, pretreatment with retinol resulted in a decrease in tyrosine phosphorylation of the EGF receptor. These results suggest that pretreatment with retinol decreases cellular proliferation seen with TGF alpha treatment by altering phospholipase C-gamma 1 response and/or EGF receptor tyrosine kinase activity. Alteration of phospholipase C-gamma 1 activity does not appear to be responsible for the inhibition of cell growth seen in the absence of TGF alpha stimulation.

TGF alpha enhances locomotion of cultured human keratinocytes.

A cDNA sequence coding for the full-length human transforming growth factor alpha (TGF alpha) precursor protein was introduced into and transcribed in cultured human keratinocytes, using a high-titer, high-expression, murine amphotropic retrovirus. Keratinocytes were shown capable of post-translationally modifying the TGF alpha primary translation product, with the subsequent formation of several cell-associated and secreted forms of TGF alpha, at least five of which, including the 50 amino acid mature species, can potentially bind and activate the epidermal growth factor receptor. Cells overexpressing the TGF alpha gene assumed a spindled morphology with long, bipolar filamentous processes and displayed increased locomotion. The soluble, mature form of TGF alpha alone also could induce the observed changes in cell shape and motility when added to keratinocyte cultures exogenously. The effects were dose dependent, and up to fourfold increases in locomotion were caused by TGF alpha in the absence of bovine pituitary extract (BPE). The addition of BPE to high concentrations of TGF alpha further enhanced keratinocyte motility to eightfold over baseline, suggesting a synergistic interaction between the two factors. These experiments demonstrate that keratinocytes can synthesize several forms of TGF alpha and that TGF alpha, besides being mitogenic, may have other important regulatory functions in keratinocytes.

Alterations in growth phenotype and radiosensitivity after fractionated irradiation of breast carcinoma cells from a single patient

Purpose : To investigate growth regulation and radiosensitivity in surviving clonogens after fractionated irradiation. Methods and Materials : Four breast carcinoma cell lines isolated from the primary tumor (21NT, 21PT) and metastases (21MT-1, 21MT-2) of a single patient were exposed to cumulative radiation doses of 30 Gy yielding cell lines designated -IR with respect to their parent. The irradiated lines were then compared to their parent for serum- and growth factor-requirements under defined media conditions, ability to proliferate in soft agar, concentration of TGF-alpha in conditioned medium, and radiosensitivity. Results : The irradiated lines showed no change in proliferative doubling times under serum- and growth factor supplemented media conditions. A single line, 21MT-1-IR, acquired a limited ability to proliferate in serum- and growth factor-deplete medium with a day 2–4 doubling time of 44.5 hr. Three lines, 21MT-1-IR, 21MT-2-IR, and 21NT-IR, formed colonies in soft agar in contrast to none of the unirradiated parent lines. There were significant 6–8 fold increases in conditioned media TGF-alpha concentrations for 21MT-2-IR and 21NT-IR cells. The 21MTl-IR and 21NT-IR cells were significantly less radiosensitive than their respective parent lines. This decrease in radiosensitivity appeared to be at least partially mediated by a released factor as the radiosensitivity of 21MT-1 cells was significantly decreased by pre-incubation with conditioned medium from 21MT-1-IR cells. Conclusion : Radiation-induced changes in growth phenotype vary with respect to clonal origin of the cell line and may influence the radiosensitivity of surviving clonogens after fractionated treatment.

Transforming growth factor alpha and atrial natriuretic peptide in white adipose tissue depots in rats.

To detect the presence in adipose tissue of peptides known to affect tissue growth and to investigate potential regional differences, epididymal and perirenal adipose tissue depots from male Sprague-Dawley rats were separated into adipocyte and stroma-vascular fractions by collagenase digestion, sequential centrifugation and filtration. Identity and integrity of the fractions were demonstrated by light and electron microscopy, while dose-response curves for angiotensin-converting enzyme (ACE) were performed, revealing maintained functional capacity of the stroma-vascular fraction. ACE, atrial natriuretic peptide (ANP), and transforming growth factor-alpha (TGF-alpha) concentrations were significantly greater in epididymal than perirenal stroma-vascular tissue. Adipocyte fractions from both depots contained significant concentrations of ANP and TGF-alpha. There was no detectable ACE in the adipocyte fractions, indicating that no contaminating stromal-vascular cells were present in these fractions. These data show significant concentrations of peptides with effects on growth in subfractions of adipose tissue and demonstrate regional differences in concentrations between fat depots.

Organ culture of psoriatic skin: effect of TGF-alpha and TGF-beta on epidermal structure in vitro.

Normal skin and uninvolved and involved psoriatic skin specimens were maintained in vitro in organ culture. The 3-4 mm punch-biopsied skin specimens were put freely into the culture medium with or without fetal calf serum, under an atmosphere of 95% O2 plus 5% CO2, and rotated at 60 rpm at 37 degrees C. In the serum-free culture medium (vitamin A-free) granular layers appeared in the involved psoriatic epidermis in culture. Addition of TGF-alpha caused normal skin and uninvolved and involved psoriatic skin specimens to become acanthotic and to degenerate easily almost to the full thickness of the epidermal layer in proportion to increasing concentrations of TGF-alpha as well as with the duration of the culture, but without disappearance of their granular layers. TGF-beta caused the normal skin and uninvolved psoriatic skin specimens to become thinned without disappearance of granular layers, but caused the involved psoriatic skin specimens to be thinned without appearance of granular layers in serum-containing medium or with their disappearance in the serum-free medium. TGF-beta also antagonized the acanthotic and degenerative effect of TGF-alpha. The results suggest that TGF-alpha and TGF-beta may partially be related to the induction of psoriatic epidermal lesions.

Transforming growth factor alpha, but not epidermal growth factor, promotes the survival of sensory neurons in vitro

Transforming growth factor alpha (TGF alpha) is a mitogenic polypeptide that is structurally homologous to epidermal growth factor (EGF) and appears to bind to the same receptor in all systems tested previously. In the present study, TGF alpha was found to enhance survival and neurite outgrowth of cultured neonatal rat dorsal root ganglion (DRG) neurons in a dose-dependent manner. This effect was observed with TGF alpha concentrations as low as 17.8 pM. By contrast, EGF at concentrations up to 83 nM was ineffective. Moreover, EGF did not antagonize the TGF alpha survival-promoting effect unless present in large excess (500-fold the concentration for which TGF alpha is effective); even in this case, only partial antagonism was achieved. Survival of neurons from nodose, trigeminal, and sympathetic ganglia was not increased by TGF alpha. Both a subpopulation of DRG neurons and of macrophages in the cultures bound iodinated TGF alpha. This binding was inhibited by excess unlabeled TGF alpha but not EGF. Our data are consistent with the possibilities that the actions of TGF alpha on DRG neurons occur indirectly via unidentified neurotrophic molecules other than NGF as well as directly on the neurons themselves. Thus, TGF alpha, in contrast to EGF, may act as a survival or maintenance factor for a subset of rat sensory neurons. Mediation of this neurotrophic effect appears to occur via a new form of TGF alpha receptor.

Enhancement of transforming growth factor-α synthesis in multicellular tumour spheroids of A431 squamous carcinoma cells

Multicellular tumour spheroids are cellular aggregates that can be prepared from many types of tumour cells. These three-dimensional structures provide a model for analysing the effects of cell-cell contact and intercellular microenvironments on phenomena such as autocrine regulation of growth factor synthesis. Autoregulation of the synthesis of transforming growth factor-alpha (TGF-alpha) was investigated at the message and protein levels in spheroid and monolayer cultures prepared from the A431 human squamous carcinoma cell line. The epidermal growth factor receptor (EGF-R) of these monolayer A431 cells had an average surface density of 2.2 x 10(6)/cell. Constitutive expression of TGF-alpha mRNA was an average of 3-fold greater in A431 spheroids than in monolayers, even for densely packed, confluent monolayers. This effect did not depend on hypoxic stress within the spheroids. TGF-alpha protein synthesis was enhanced in comparison with that in monolayer culture, reaching a value of up to 2-fold greater on a per cell basis. These results are discussed in the context of a TGF-alpha/EGF-R autocrine loop operating within cells that produce high local concentrations of TGF-alpha in the three-dimensional architecture of a spheroid.

Transforming growth factor alpha induces collagen degradation and cell migration in differentiating human epidermal raft cultures.

When cultured on plastic and treated with transforming growth factor alpha (TGF alpha), human keratinocytes exhibit an increase in proliferation at the colony periphery, apparently as a consequence of enhanced cell migration (Barrandon and Green, 1987). To investigate the effects of TGF alpha on a differentiating stratified squamous epithelium and to begin to examine the molecular basis mediating this influence, we cultured human epidermal cells on a gelled lattice of collagen and fibroblasts, floating on the air-liquid interface. Under these conditions, raft cultures differentiate and exhibit morphological and biochemical features of human skin in vivo (Asselineau et al., 1986; Kopan et al., 1987). When 3-wk-old raft cultures were treated with TGF alpha, basal cells showed a marked increase in cell proliferation. At elevated concentrations of TGF alpha, the organization of cells within the artificial tissue changed and islands of basal cells entered the collagen matrix. Biochemical analysis of the response revealed that type I collagenase and gelatinase were induced by keratinocytes within 12 h after TGF alpha treatment. In contrast, invasion of basal cells into the collagen matrix was not significant until 48-72 h post-treatment, suggesting that collagenase and gelatinase production may be a prerequisite to this phenomenon. These results have important implications for the possible role of TGF alpha in squamous cell carcinoma and tumor invasion.

Prognostic implication of transforming growth factor α in adenocarcinoma of the lung – an immunohistochemical study

We examined for transforming growth factor alpha (TGF alpha) in adenocarcinomatous lesions of the lung tissues excised from 138 patients, with use of the avidin-biotin-peroxidase complex (ABC) method. TGF alpha was present in the cytoplasm of the adenocarcinoma. Our objective was to determine if TGF alpha could serve as a prognostic parameter. We divided 138 patients into two groups according to the concentration of TGF alpha. Ninety-two patients had a high concentration of TGF alpha, in over 75% of the tumour cells, while 46 had a low concentration, that is in less than 75% of the cells. The 5-year survival rates of patients with high TGF alpha and low TGF alpha were 39% and 64%, respectively (P less than 0.05). Our data suggest that evidence of a high immunoreactivity of TGF alpha can serve as a prognostic parameter in adenocarcinoma of the lung.

Transforming growth factor‐alpha augments meiotic maturation of cumulus cell‐enclosed mouse oocytes

Growth factors have been shown to play an important role in the regulation of ovarian function. In this study, we examined the effects of transforming growth factor-alpha (TGF-alpha) on the meiotic maturation of immature mouse oocytes in vitro. Cumulus cell-enclosed oocytes were exposed to TGF-alpha with or without the meiotic inhibitor hypoxanthine (HX), and oocyte maturation was assessed by germinal vesicle breakdown (GVBD). Likewise, mechanically denuded oocytes were examined for GVBD following exposure to HX and TGF-alpha. When cumulus cell-enclosed oocytes were exposed to TGF-alpha (1 microgram/ml) in the presence of HX (4 mM), an increase in GVBD was observed first after 5 hours of culture. Maximal stimulation was reached at 24 hours when 70% of the oocytes underwent maturation in the presence of TGF-alpha and HX as compared to 33% with HX only. Concentrations of TGF-alpha as low as 0.1 ng/ml produced a similar stimulatory response after 24 hours of culture. Spontaneous maturation in the presence of TGF-alpha, but without HX, was also enhanced. The stimulation of GVBD by TGF-alpha showed an increase over time both with and without HX. When denuded oocytes were exposed to TGF-alpha in the presence of HX, no effect was observed. Our results suggest that TGF-alpha is a potent stimulator of mouse oocyte maturation in vitro and that its effect is mediated by the surrounding cumulus cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of transforming growth factor-alpha in primary human colon and lung carcinomas

The expression of TGF-alpha in human colon and lung carcinoma cell lines has been reported previously, but its expression in primary tumours has not been described in detail. We have used the radio-immunoassay method to measure the specific content of immunoreactive TGF-alpha in the acid ethanol extracts of normal and cancerous tissues of human colon and lung. The average TGF-alpha content of colon carcinomas is 4 times that of the normal mucosa, and for non-small cell lung carcinomas it is twice that of the normal parenchyma. Because of variability in the TGF-alpha expression among individuals and in different segments of colon and lobes of lung, the ratio of TGF-alpha content of paired tumour and normal tissue was also calculated. On average, the tumour/normal ratio for colon carcinoma is higher than that for lung carcinoma. Although 55% of colon tumours show a ratio 4 times, or greater, only 33% of lung carcinomas demonstrate this ratio. The level of TGF-alpha in both colon and lung carcinomas does not correlate with histological type stage, grade nor degree of desmoplasia of these tumours. Northern blot analysis of total cellular RNA confirms the expression of an approximately 4.8 kb TGF-alpha mRNA in normal colonic mucosa and lung parenchyma. However, in contrast to the results of radio-immunoassay, significant over-expression of TGF-alpha mRNA is uncommon in primary human colon carcinomas.

Transforming growth factor alpha in developing rats

Transforming growth factor-alpha (TGF-alpha) concentrations were measured in lung, brain, liver, and kidney of rats at three different ages (20 days gestation and 9 and 50 days postnatal). TGF-alpha concentrations were maximal in the lung and brain by 20 days of gestation and showed minimal changes during nursing (day 9) and young adulthood (day 50). The liver, which also showed maximal TGF-alpha concentration by 20 days of gestation, demonstrated a progressive reduction with age to nadir values in the young adult. In contrast to the pattern in other tissues, kidney had the lowest concentration of TGF-alpha in late gestation and showed an increase by 50 days of age. As TGF-alpha acts via the epidermal growth factor (EGF) receptor, its function in development may be analogous to that of EGF. Thus TGF-alpha may have a role in lung maturation and postinjury repair, liver repair and regeneration, and neuronal cell growth.

Modulation of Hen Granulosa Cell Steroidogenesis and Plasminogen Activator Activity by Transforming Growth Factor Alpha

Studies were conducted with chicken granulosa cells to evaluate the relative efficacy of human recombinant transforming growth factor alpha (TGF alpha) versus murine epidermal growth factor (EGF) to affect cyclic adenosine monophosphate (cAMP) accumulation and progesterone production stimulated by luteinizing hormone (LH) or steroid output induced by a cAMP analogue, and to modulate plasminogen activator (PA) activity. Increasing concentrations of EGF (33-328 nM) and TGF alpha (0.04-18 nM) were found to inhibit cAMP formation stimulated by LH in a dose-dependent manner, with calculated half-maximal inhibitory doses (ID50's) of 97.1 and 0.27 nM, respectively. Similarly, a 470-fold difference in the ability of TGF alpha (ID50 = 0.13 nM) versus EGF (ID50 = 61.3 nM) to half-maximally suppress LH-induced progesterone production was observed in the same cells. Progesterone production stimulated by a cAMP analogue (8-bromo-cAMP, 1 mM) was also attenuated by EGF (ID50 = 75.9 nM) and TGF alpha (ID50 = 0.08 nM), suggesting a post-cAMP site of inhibition by these growth factors on steroidogenesis. Finally, a 260-fold to 330-fold difference in the efficacy of TGF alpha versus EGF to half-maximally stimulate cell-associated and secreted PA activity was observed. From these data, we propose that TGF alpha may serve an important role in regulating follicular growth and maturation in the domestic hen via its ability to affect granulosa cell steroidogenesis and plasminogen activator activity.