Lack of effect of epidermal growth factor treatment in late-pregnant ewes on subsequent lactation

ERBB Receptors and Their Ligands in the Developing Mammary Glands of Different Species: Fifteen Characters in Search of an Author

The ERBB tyrosine kinase receptors and their ligands belong to a complex family that has diverse biological effects and expression profiles in the developing mammary glands, where its members play an essential role in translating hormone signals into local effects. While our understanding of these processes stems mostly from mouse models, there is the potential for differences in how this family functions in the mammary glands of other species, particularly in light of their unique histomorphological features. Herein we review the postnatal distribution and function of ERBB receptors and their ligands in the mammary glands of rodents and humans, as well as for livestock and companion animals. Our analysis highlights the diverse biology for this family and its members across species, the regulation of their expression, and how their roles and functions might be modulated by varying stromal composition and hormone interactions. Given that ERBB receptors and their ligands have the potential to influence processes ranging from normal mammary development to diseased states such as cancer and/or mastitis, both in human and veterinary medicine, a more complete understanding of their biological functions should help to direct future research and the identification of new therapeutic targets.

Milk Proteins-Their Biological Activities and Use in Cosmetics and Dermatology

Milk and colostrum have high biological potential, and due to their natural origin and non-toxicity, they have many uses in cosmetics and dermatology. Research is ongoing on their potential application in other fields of medicine, but there are still few results; most of the published ones are included in this review. These natural products are especially rich in proteins, such as casein, β-lactoglobulin, α-lactalbumin, lactoferrin, immunoglobulins, lactoperoxidase, lysozyme, and growth factors, and possess various antibacterial, antifungal, antiviral, anticancer, antioxidant, immunomodulatory properties, etc. This review describes the physico-chemical properties of milk and colostrum proteins and the natural functions they perform in the body and compares their composition between animal species (cows, goats, and sheep). The milk- and colostrum-based products can be used in dietary supplementation and for performing immunomodulatory functions; they can enhance the effects of certain drugs and can have a lethal effect on pathogenic microorganisms. Milk products are widely used in the treatment of dermatological diseases for promoting the healing of chronic wounds, hastening tissue regeneration, and the treatment of acne vulgaris or plaque psoriasis. They are also increasingly regarded as active ingredients that can improve the condition of the skin by reducing the number of acne lesions and blackheads, regulating sebum secretion, ameliorating inflammatory changes as well as bestowing a range of moisturizing, protective, toning, smoothing, anti-irritation, whitening, soothing, and antiaging effects.

Lactogenic hormones and extracellular matrix regulate expression of IGF-1 linked to MMTV-LTR in mammary epithelial cells

The cell line MD-IGF-1, containing an ovine IGF-1 cDNA driven by the mouse mammary tumor virus-long terminal repeat (MMTV-LTR) promoter, was used to study expression of IGF-1 linked to the MMTV-LTR in bovine mammary epithelial cells in response to various hormonal and substratum stimuli. Acute sensitivity of the MMTV-LTR promoter to glucocorticoids and sex steroids was ascertained by transient transfection of parental MAC-T cells with an MMTV-CAT construct. Specifically, CAT activity was induced by glucocorticoids, but not by 17 beta-estradiol or progesterone. Induction of MD-IGF-1 cells with dexamethasone (DEX) alone triggered a 29.5-fold increase in secretion of recombinant IGF-1 (348.9 vs 11.8 pg/micrograms DNA), and stimulated a 1.7-fold increase in total DNA within 72 h. Growth of MD-IGF-1 cells was enhanced by exogenous IGF-1, insulin, and TGF-alpha. In contrast, TGF-beta inhibited cell proliferation, while epidermal growth factor, estrogen, progesterone, and testosterone had no effect. Extracellular matrix from the Engelbreth-Holm-Swarm (EHS) tumor, in the presence of DEX, prolactin (PRL), and insulin stimulated a 29.4-fold increase in secretion of IGF-1 (591.9 pg/microgram DNA), compared with cells in absence of hormones (20.1 pg/micrograms DNA). EHS and DEX plus PRL triggered a 63.2-fold increase in IGF-1 secretion (689.1 pg/micrograms DNA), compared with MD-IGF-1 cells cultured on plastic (10.9 pg/micrograms DNA), in the absence of hormones. These data indicate that the MMTV-LTR is regulated by both lactogenic hormones and extracellular matrix in MD-IGF-1 cells and that the MMTV-LTR may be a useful regulatory element for targeting expression of foreign proteins in bovine mammary epithelial cells.

Role of epidermal growth factor and transforming growth factors in mammary development and lactation

Epidermal growth factor, transforming growth factor-alpha, and transforming growth factor-beta 1 are potent effectors of mammary growth that work in concert with endocrine hormones, such as estrogen, progesterone, corticosteroids, and prolactin. Estrogen and progesterone stimulate production of epidermal growth factor or transforming growth factor-alpha to stimulate mammary growth. Epidermal growth factor and prolactin synergize in whole organ culture to cause lobulo-alveolar development and to alter the profile of synthesized milk proteins. Transforming growth factor-beta 1 inhibits mammary development of prepubertal mice. However, once the gland is committed to differentiation, transforming growth factor-beta 1 no longer affects mammary morphogenesis. The role of transforming growth factor-beta 1 in milk protein synthesis is unknown. Transforming growth factor-alpha and -beta 1 mRNA have both been identified in the mammary gland of cows. The gland has epidermal growth factor receptors, and epidermal growth factor or transforming growth factor-alpha can stimulate proliferation of mammary epithelial cells in vitro. The role of transforming growth factor-beta 1 in bovine mammary tissue has not been studied. An understanding of the role of epidermal growth factor, the transforming growth factors, and their interactions with endocrine hormones will lead to a more complete understanding of how mammary development and lactation are regulated.

Epidermal growth factor alters the electrolyte profile of lactating ewes (Ovis aries)

1. Lactating ewes were treated with mouse epidermal growth factor (EGF) at a dose rate of 0.5 mg/day for 4 days and its effects on the electrolyte profile were observed. 2. There was no effect of EGF on plasma concentrations of sodium or potassium, although urinary and total (in urine and milk) losses of both were reduced. 3. EGF-induced hypocalcaemia was associated with reduced milk calcium secretion and increased urinary calcium excretion whereas EGF-induced hypermagnesaemia was associated with reduced urinary and total magnesium losses. 4. Glomerular filtration rate was reduced during EGF infusion. 5. Chronic intravenous EGF infusion affects the electrolyte profile by altering electrolyte secretion by the mammary gland and renal electrolyte excretion.

Localization of Epidermal Growth Factor Immunoreactivity in Sheep Skin During Wool Follicle Development

Interactions among the cells and matrices of the epidermis and mesenchyme of skin are essential for hair follicle initiation and development. The identification of receptors for epidermal growth factor (EGF) on epithelial components of the follicle during growth has suggested that the ligand participates in some of these events. We have used affinity-purified antibodies together with an alkaline phosphatase detection procedure to investigate the distribution of EGF in the skin of the sheep during wool follicle formation. Immunoreactivity was restricted to the periderm and intermediate layers of fetal epidermis at 55 d of gestation, when the first wave of wool follicles are initiated. This particular distribution persisted during subsequent development but never became associated with the basal cells of the epidermis. The activity was lost around 118 d, coinciding with sloughing of the periderm. No immunoreactivity was found in the plugs or the dermal condensations of the developing follicles. At approximately 105 d of gestation, however, reactions were detected in the outer root sheath as the follicles matured and in the differentiating cells of the sebaceous glands. A similar distribution pattern was also noted at 140 d, just prior to birth, and in adult animals, indicating that EGF was sequestered and perhaps synthesized within the follicle. The presence of immunoreactive material was also associated with the pilary canals and the skin surface, suggesting that this may have had its origin in the sebaceous glands. We examined this using a radioreceptor assay for EGF. Material washed from the skin surface and sebaceous gland extracts were found to displace 125I-EGF from rat liver membranes, in parallel with mouse EGF.