Expression of growth hormone receptor in the bovine mammary gland during prenatal development

Abstract

Growth hormone (GH) is known to play a key role in postnatal growth and differentiation. The role of GH and its receptor (GHR) in prenatal development, however, is still controversial. Using reverse transcription polymerase chain reaction (RT-PCR), in situ hybridization (ISH) and immunohistochemistry we demonstrated the presence of GHR mRNA and protein in bovine mammary glands during fetal development. RT-PCR revealed GHR transcripts in fetal mammary glands from the third to the ninth month of pregnancy. By non-radioactive ISH, GHR mRNA was localized in the glandular epithelium, the surrounding mesenchymal cells, endothelial cells of vessels and in the stratum basale of the epidermis of fetal mammary glands. From the sixth month of fetal life onwards, GHR transcripts were also found in the cytoplasm of adipocytes. Immunohistochemical studies using the monoclonal antibody mAb 263 revealed the same distribution pattern as the mRNA. Our results imply that the growth hormone receptor is distinctly expressed in the immature mammary gland, suggesting that GH is involved in growth and differentiation of the fetal mammary gland.

Effects of adenosine 5'-triphosphate and growth hormone on cellular H+ transport and calcium ion concentrations in cloned bovine mammary epithelial cells

“…The action of GH has been thought to increase lipolysis in adipocytes by an increased response and sensitivity to lipolytic ( -adrenergic) agonists and a decreased response and sensitivity to antilipolytic factors such as adenosine and prostaglandin E (Doris et al 1998). Although a direct action of GH on mammary epithelial cells is questionable because of the scarcity of GH receptor proteins, a line of evidence suggesting the expression of GH receptor mRNA is accumulating in bovine (Hauser et al 1990, Knabel et al 1998, mouse (Ilkbahar et al 1995), rabbit (Jammes et al 1991) and rat (Lincoln et al 1990, Tiong & Herington 1991) mammary gland cells. As shown in Fig.…”

“…First, attempts to detect the existence of the GH receptor protein in mammary tissue have been unsuccessful (Gertler et al 1983, Akers 1985, Keyes & Dijane 1988 except for one report (Glimm et al 1990). Secondly, although the expression of the GH receptor mRNA is apparent in adult and fetal ruminant (Hauser et al 1990, Jammes et al 1991, Scott et al 1992, Knabel et al 1998 and rodent (Tiong & Herington 1991, Ilkbahar et al 1995, 1999 mammary gland cells, the close arterial infusion of GH does not affect milk yield, while IGF-I causes a significant increase (McDowell et al 1987, Prosser & Davis 1992, Prosser et al 1990. Thirdly, the biological actions in vitro of GH on bovine and rat MEC are ill defined (Gerter et al 1983, Keyes et al 1991, Walden et al 1998 despite the exception that GH has been reported to increase the production of -lactoglobulin from an ovine mammary heterogeneous cell population that contained epithelial, myoepithelial and fibroblast-like cells (Ilan et al 1998).…”

Regulation of Mammary Development as It Relates to Changes in Milk Production Efficiency

“…In addition, expression of GH receptor has been detected in mammary tissue (Knabel et al, 1998;Sinowatz et al, 2000;Plath-Gabler et al, 2001). The GH receptor belongs to a superfamily of transmembrane receptors, of which PRL receptor is a member (Postel-Vinay & Kelly, 1996).…”