[Milk ceruloplasmin as a physiological source of nutritional copper in early ontogenesis in mammals].

This work elucidates the role of ceruloplasmin (Cp): the main soluble copper containing glycoprotein, in newborn infant copper metabolism. An over 3-fold drop of Cp and copper concentration in samples of skimmed milk from 2 to 5 days of lactation was demonstrated. It has been shown that [125I]Cp of the breast milk is discovered in the blood plasma after its was administered per os to 6-day old rats. In the body, [125I]Cp was specifically bound to cells and lost copper ions. Alternatively, after copper metabolism change to adult type, milk [125I]Cp isn't carried from gastrointestinal tract to the blood. During 8 days, newborn rats were fed with baby formula and we have found that in this case changing of the copper metabolism type takes place earlier in contrast to the litter fed by females. Transcription of the Cp gene activated in liver, Cp and the copper ions concentration in the blood plasma increased proportionally, whereas in liver the copper concentration is decreased. In the brain, changes typical for adult copper metabolism, were not discovered. But in cerebrospinal fluid copper and Cp concentration sharply increased. The role of milk Cp in controlling the copper balance in newborn rats and the tissue-specific mechanism of Cp gene activity regulation are under discussion.

[Age-related features of ceruloplasmin biosynthesis and distribution in rats]. / Vozrastnye osobennosti biosinteza i raspredeleniia tseruloplazmina v organizme krys.

Biosynthesis of ceruloplasmin, a copper-containing glycoprotein, which plays an important role in copper transfer and bidirectional iron transport in vertebrates, was studied in 7-day old rats characterized by the embryonic type of copper metabolism. In addition to the liver, copper is synthesized in the lungs, brain, and kidneys. The appearance of labeled ceruloplasmin in the blood flow coincides with the time of liberation of de novo synthesized ceruloplasmin from the liver. [14C]-Ceruloplasmin is absorbed from the blood flow by cells of the heart, lung, and kidneys and binds to erythrocytes. The polypeptide ceruloplasmin chain does not enter the brain cells from the blood flow. Immunoreactive polypeptides of the ceruloplasmin receptor were found using immunoblotting in plasma membranes of the heart, liver, kidneys, and erythrocytes, rather than in those of the brain. It was shown by reverse transcription coupled with PCR using selective primers these cells contain molecular forms of ceruloplasmin mRNAs programming the synthesis of both secretory ceruloplasmin and ceruloplasmin connected with the plasma membrane via the glycosyl phosphatidylinositol anchor. After transition to the adult type of copper metabolism, the blood serum contents of copper and ceruloplasmin sharply increase, while the content of CP in the cerebrospinal fluid, as measured according to the oxidase and antigen activities, and copper concentration, as determined by atom-absorption spectrometry, remain low. Ontogenetic features of the system ensuring the copper homeostasis in mammals are discussed.

[Effects of infant formula feeding on the distribution of copper in the body of 8-day-old rats]. / Vliianie iskusstvennogo vskarmlivaniia na raspredelenie medi v organizme 8-dnevnykh krysiat.

The oxidase activity of ceruloplasmin (Cp, EC 1.16.3.1), the content of immunoreactive Cp and copper ion concentration were measured in the serum of eight day-old rats receiving either breast feeding (control group) or commercial nutritive mixture which has been recommended for the newborn children beginning from zero age (experimental group). It was shown that the artificial feeding caused almost 3-fold increase of Cp oxidase activity and copper content in the serum when compared to age-matched controls. No changes in the copper content per Cp molecule were observed. Dot-hybridization of the total liver polyribosomal RNA with Cp [32P]cDNA showed that the increased Cp level in the blood of the rats of experimental group correlated well with the level of expression of Cp gene. The copper content in the liver of experimental rats was two times lower that in control animals while no differences was found in the brain copper content between two groups of rats. The role of the regulation of Cp gene expression in the lactating mammary gland and of milk Cp in the copper homeostasis in the newborn body is discussed.