Human fetuin/α2 HS glycoprotein in colloid and parenchymal cells in human fetal pituitary gland

Abstract

An immunohistochemical study was undertaken, in an attempt to identify the acidic glycoprotein(s) present in colloid and in parenchymal cells in human fetal pituitary gland. As the colloid has been proposed to represent disintegrating cells, a series of antibodies against plasma glycoproteins and plasma proteins was applied; their presence intracellularly would generally be an indicator of plasma membrane leakage in dying parenchymal cells. In tissue sections from 9- to 20-week-old fetuses, the colloid showed prominent staining with an antibody to human fetuin/alpha 2 HS glycoprotein. Anti-alpha 2-HS glycoprotein labelled parenchymal cells in pars anterior and intermedia. Apart from a minor immunoreactivity for alpha 1 beta glycoprotein, no other plasma glycoprotein was seen in colloid or parenchymal cells. An antibody against bovine fetuin showed staining of the colloid and of some parenchymal cells in pars distalis and intermedia; the plasma and stroma of the pituitary gland were unstained. In contrast, the anti-human plasma protein antibodies all stained the stroma. The presence of alpha 2 HS glycoprotein in parenchymal cells and absence of other plasma glycoproteins imply integrity of the parenchymal cell plasma membrane. Thus, alpha 2 HS glycoprotein is either synthesized locally or taken up specifically in the parenchymal cells, which are proposed to participate in the formation of colloid. It is suggested that alpha 2 HS glycoprotein is part of a homeostatic system, which controls remodelling and physiological cell death during development.

Multifunctional Roles for Serum Protein Fetuin-A in Inhibition of Human Vascular Smooth Muscle Cell Calcification

“…A similar localization has been described in colloid and parenchymal cells in the human fetal pituitary gland, where it was suggested that fetuin-A was "tagging" cells for elimination (38). In support of this, our data and other recent reports show that fetuin-A is important in phagocytosis (39).…”

Plasma biomarker proteins for detection of human growth hormone administration in athletes

“…AHSG, also known as Fetuin-A, is a ~40 kDa protein that is synthesized and secreted by hepatocytes into the plasma and acts as a carrier protein 24 . AHSG is also expressed in the pituitary gland 32 . It has been shown that AHSG inhibits the action of Leukemia inhibitory factor (LIF) in pituitary corticotropes 33 .…”