Secretion of sulphated respiratory-tract mucins by cultured tracheal explants

Abstract

PROCEEDINGS OF THE BIOCHEMICAL SOCIETY common and resemble metallothionein, a Cd2+_ containing protein of unknown function isolated by Kagi & Vallee (1960, 1961) from horse kidney. The subsequent isolation of 'metallothioneins' from human kidney (Pulido, Kagi & Vallee, 1965), from the livers of Cd2+-injected rabbits (Piscator, 1964) and from the livers and kidneys of rats after intravenous injection of 203HgCl2 (Jakubowski, Piotrowski & Trojanowska, 1970) suggests that these proteins constitute detoxifying mechanisms against certain heavy metals. At least in the male rat, the Cd2+-binding protein does not appear to be a normal component of the liver, but is induced in response to Cd2+. It is synthesized also in response to excess of Zn2+ and, in livers of animals pre-injected 24-48h previously with Zn2+, parenterally administered Cd2+ accumulates, and is thus immobilized, more rapidly than in the normal liver. This provides a possible explanation for the protection by Zn2+ against Cd2+ injury to the testes, particularly as it is known that Zn2+ has maximal activity when administered at least 24h before Cd2+ (Mason & Young, 1967).

Biosynthesis of respiratory-tract mucins. Incorporation of radioactive precursors into glycoproteins by canine tracheal explants in vitro

“…This demonstration of a macromolecule containing carbohydrate in tissue extracts does not prove that the material is actually a secretory product. More recently the incorporation of labelled precursors into macromolecules secreted into the culture medium has been demonstrated (Ellis & Stahl, 1971;Kent et al, 1971).…”

“…More recently studies have been made of the macromolecules secreted by tracheobronchial explants (Kent et al, 1969;Stahl & Ellis, 1970 are concerned with the further development of these techniques, together with the fractionation and characterization of the radioactive macromolecules. Preliminary reports have been published (Stahl & Ellis, 1970;Ellis & Stahl, 1971).…”