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Background: Conditions not directly related to copper nutriture, such as pregnancy, infections and inflammation, which increase serum copper concentration even during copper deprivation, may be expected to conceal changes in copper status. It has been suggested that the specific enzymatic activity of ceruloplasmin (activity per unit mass of enzyme protein) may be a sensitive indicator of copper status and is not affected by factors such as hormones or sex. In this study, we investigated the behaviour of specific oxidase activity of ceruloplasmin and the copper/ceruloplasmin ratio in pregnant women., Methods: Copper, immunoreactive ceruloplasmin and its oxidase activity were determined in serum from 52 women in the last trimester of normal pregnancy, and in 50 control women of similar age living in the same area and who were not taking oral contraceptives. The results are expressed as mean+/-S.E.M., Results: In the group of pregnant women, significantly higher serum levels of copper, ceruloplasmin and its oxidase activity were found than in the control group (p < 0.001). In both groups, a high correlation was found between these biochemical variables (r > or =0.905, p < 0.001). However, in the group of pregnant women the specific oxidase activity for ceruloplasmin (364.4+/-3.3 vs. 407.5+/-3.8 U/g) and the copper/ceruloplasmin ratio (2.82+/-0.03 vs. 3.19+/-0.04 microg/mg) were significantly lower than in the control group (p < 0.001)., Conclusions: Although pregnancy accelerates the rate of ceruloplasmin protein synthesis and release with an increase of serum copper, the decrease in specific oxidase activity of circulating ceruloplasmin would be an indicator of the degree of depletion of the mother's copper deposits in order to deal with the foetus' needs.

In a study of 50 full-term newborns, we found serum levels of ceruloplasmin, its oxidase activity and specific oxidase activity (activity per unit mass of enzyme protein) which were significantly lower than in adult subjects (p<0.001). A significant correlation was obtained between the specific oxidase activity of the neonatal ceruloplasmin and the transferrin/alpha-fetoprotein ratio (p<0.01), which reflects the maturity of the fetal hepatocyte through its ability to synthesise fetal- and non-fetal-associated proteins. The lower specific oxidase activity of the ceruloplasmin in newborns would be due to a higher relative proportion of apoprotein, and/or other molecular forms with a poor copper content in the oxidase sites. This could be due to an inability to transfer copper into a common intracellular pool for holoceruloplasmin synthesis and biliary copper excretion. A high interindividual variability was found for the specific oxidase activity of the neonatal ceruloplasmin, and in the newborns with higher levels of ceruloplasmin this, from a catalytic point of view, is more similar to the adult form.

Forty adult patients (30 women and 10 men) with rheumatoid arthritis (RA), treated with nonsteroidal anti-inflammatory drugs, were studied. Serum levels of immunoreactive ceruloplasmin, oxidase activity of the ceruloplasmin and total copper, as well as the specific oxidase activity (enzyme activity per unit of mass) and the copper/immunoreactive ceruloplasmin relationship were significantly higher in the group of patients than in the healthy control group (p < 0.001). However, no significant difference was found for the concentration of non-ceruloplasmin copper between both groups. A statistically significant negative correlation was obtained for the concentration of serum thiobarbituric acid-reacting substances with the immunoreactive ceruloplasmin and its oxidase activity in the group of patients (p < 0.005). These results suggest that in RA increases of serum copper are produced at the expense of the fraction linked to the ceruloplasmin, diminishing the proportion of apoceruloplasmin and other forms poor in copper. Although the increase in the serum concentration of ceruloplasmin might offer an additional safeguard against oxidative stress. it does not appear to have a beneficial effect upon the activity of the illness as evaluated by means the biological inflammation markers C-reactive protein, erythrocyte sedimentation rate and sialic acid.

Using an electrophoretic technique on cellulose acetate, three multiple forms of the 5'-nucleotidase (5'NU) with mobilities alpha 1, alpha 2, and beta appear in the serum of healthy subjects. The difference between the alpha 1 and alpha 2 isoforms lies in their sialylation degree, the alpha 2-5'NU being a de-sialylated form. In 147 patients with different hepatobiliary diseases the alpha 2 isoform was present in only 19% of cases, and there was no significant difference in the activity of total 5'NU, alpha 1-5'NU and beta-5'NU between patients with or without alpha 2-5'NU, alpha 1-5'NU and beta-5'NU (P < 0.001), as with other biochemical indicators of liver damage. It is suggested that in hepatobiliary diseases an increase of the sialylation of serum 5'NU occurs, which would explain the absence of the desialylated alpha 2 isoform in the majority of cases. However, the decrease of hepatic receptors of asialoglycoproteins would lead to an increase of this de-sialylated isoform in the serum of certain patients.

We compared oxygenation and derivatization of hemoglobin for the hematofluorometric determination of erythrocyte zinc protoporphyrin (ZPP). No statistically significant differences were found when the volume ratio of sample to ProtoFluor reagent (which converts hemoglobin to cyanohemoglobin) was changed from 1:1 to 1:4. With the derivatizing reagent, results were significantly higher than those obtained after thorough aeration of the blood sample (P < 0.001). The differences between the results obtained by the two procedures were greater for ZPP values in the reference range. Although the correlation between methods was high (r = 0.997), interconversion of the results by means of the regression equation was not acceptable because the standard error of the estimate from the regression (Syix = 0.36 micrograms/g hemoglobin) was greater than the error acceptable medically (criterion of Harris: Arch Pathol Lab Med 1988; 112:416-20).

A comparison between procedures for the determination of erythrocyte zinc-protoporphyrin (ZPP) in an AVIV Mod. 206 Haematofluorometer was performed. Initial readings decrease with time, reaching a stability at 6-8 min. This fact cannot be accounted by ZPP photodegradation. High correlation coefficients (r greater than or equal to 0.994) were obtained when values from initial readings were compared with values obtained from readings after ten minutes and with values obtained using saline washed erythrocytes, although in all cases the difference of means were statistically and clinically significant. The use of "ProtoFluor Reagent", which converts haemoglobin to cyanohaemoglobin, led to significantly higher results than those obtained after aeration of the sample, although the correlation between both series of values was also excellent (r = 0.997). No statistically significant differences were found when the ratio sample: ProtoFluor Reagent was changed. These results demonstrate the need for a careful standardization of the operation procedure in the use of the haematofluorometer.

In a group of 76 clinically healthy human volunteers, we found a high correlation (r = 0.997, p less than 0.001) between the ceruloplasmin oxidase activities in serum (mean 127.2 U/l) and plasma (mean 124.0 U/l). Similarly high correlation was observed for immunoreactive ceruloplasmin, which was assayed in 65 samples (r = 0.993, p less than 0.001), with means of 306.1 mg/l in serum and 296.4 mg/l in plasma. Although the difference between the means measured in serum and plasma is in both cases statistically significant, it is clinically irrelevant according to the criteria of the College of American Pathologists. Finally, a high correlation between serum and plasma concentrations (r = 0.970, p less than 0.001, N = 32) was also found for acid alpha 1-glycoprotein, whose sialic acid content is greater than that of ceruloplasmin; in this case there was no statistically significant difference between the means. These results suggest that in humans, ceruloplasmin does not bind to erythrocyte and/or platelet membranes via sialyl groups during clotting, which disagrees with the hypothesis of Paynter (Aust. J. Biol. Sci. (1982) 35, 353--361) in cows and sheep.