Disease relevance of TGF-A

• Mucous cell hyperplasia and the diminution of parietal cell number are seen in a diverse range of disease states and may be mediated by host growth factors such as Transforming growth factor-alpha [1].

High impact information on TGF-A

• 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 [2].
• Transforming growth factor alpha gene expression and peptide localization in porcine ovarian follicles [3].
• The present study was undertaken to determine transforming growth factor alpha (TGF alpha) gene expression in various components of medium-sized porcine ovarian follicles by reverse transcription-polymerase chain reaction, and to localize the peptide during folliculogenesis by immunocytochemistry [3].
• Immunolocalization studies revealed intense TGF alpha staining in cumulus and granulosa cells of all stages of follicular development [3].
• No TGF alpha mRNA was detected in the oocyte [3].

Biological context of TGF-A

• TGF-alpha immunoreactivity was observed in epithelial tissues of the skin but was not co-localized with cell proliferation markers [4].
• Plasma FSH concentrations were high during the follicular phase in ewes treated with TGF-alpha (P < 0.05) [5].
• Eleven ewes with an autotransplanted ovary received, by ovarian arterial infusion, either 5 micrograms/h recombinant rat TGF alpha (n = 6) or placebo (n = 5) for 12 h on day 10 of the luteal phase [6].
• The presence of receptors for EGF/TGF-alpha suggests that these factors could be involved in the regulation of embryonic development and fetal growth [7].
• The observations that cell proliferation continued in the bulb, that glycogen was present and that soft keratins were expressed in these cells suggest that the bulb cell population was induced to differentiate into an ORS phenotype by EGF and TGF alpha [8].

Anatomical context of TGF-A

• A strong signal for TGF alpha transcript was detected in cumulus and granulosa cells, whereas the signal in theca cells was very weak but detectable [3].
• Primary ovine oviduct cell cultures express the transcripts for IGF-II, IGF-I, TGF alpha, bFGF, TGF beta 1, and the receptors for insulin and IGF-I, suggesting that paracrine growth factor circuits may exist between the oviduct epithelium and the early ovine embryo [9].
• DNA synthesis by mammary alveolar epithelial cells cultured on collagen gels was increased twofold by TGF-alpha (maximum response at 10 micrograms/l; 1.8 nmol/l) but not by EGF [10].
• Transforming growth factor-alpha: receptor binding and action on DNA synthesis in the sheep mammary gland [10].
• Localization and characterization of EGF/TGF-alpha receptors on peri-implantation trophoblast in sheep [7].

Associations of TGF-A with chemical compounds

• Infusion of TGF alpha resulted in a significant (P < 0.05) depression in the amplitude of the pulsatile response of oestradiol and androstenedione secretion to the GnRH-induced LH pulse at the end of the infusion [6].
• In the presence of heparin, TGF-alpha showed synergistic interactions with insulin or IGF-I [11].
• We conclude that direct arterial infusion of TGF alpha results in acute inhibition of ovarian steroid and inhibin secretion that is associated with induction of atresia in the population of large follicles [6].
• Luteal phase progesterone secretion was also acutely inhibited (P < 0.001) by infusion of TGF alpha, and in one treated ewe progesterone secretion was elevated 48-84 h after PGF2 alpha [6].
• Moreover, RT-PCR detected the expression of TGF-alpha mRNA in the rumen and abomasum and that of EGF in the abomasum, implying that these stomachs possibly supply, in part, EGF-LBA to the luminal fluid [12].

Other interactions of TGF-A

• DNA synthesis was stimulated by amphiregulin and TGF-alpha increased the maximum response [11].
• The putative local factors tested included insulin-like growth factor-I (IGF-I LR3 analogue), transforming growth factor alpha (TGF alpha) or epidermal growth factor (EGF) and inhibin A [13].

Analytical, diagnostic and therapeutic context of TGF-A

• In unoperated liver, gel chromatography showed all TGF alpha immunoactivity to be in fractions corresponding to known TGF alpha precursors (15-30 kilodaltons) [2].
• Three crossbred ewes synchronized for oestrus with ovarian autotransplants were infused with TGF-alpha (30 micrograms in 12 h) via the ovarian artery for 12 h before withdrawal of progestagen pessary [5].
• Transcriptional expression of EGF and TGF-alpha mRNA was demonstrated in both glands by reverse transcription-polymerase chain reaction (RT-PCR) [12].
• Both TGF alpha and EGF stimulated granulosa and thecal cell proliferation in vitro in a dose-responsive manner and concomitantly inhibited hormone production, whereas intra-arterial infusion of TGF alpha in vivo resulted in induction of atresia in large antral follicles and an acute fall in ovarian hormone secretion [13].

References