A radioimmunoassay for quantifying carbonic anhydrase isozymes in crude lysates

Measurement of human erythrocyte CAI and CAII in adult, newborn, and fetal blood

OBJECTIVE

The aim of the present study was to determine the erythrocyte CAI and CAII concentrations in fetal blood over a wide gestational range, and compare levels to those found in neonates and adults.

METHODS

Human erythrocyte CAI and CAII concentrations were measured in fetal (n=38), neonatal (n=10) and adult (n=30) blood, using enzyme-linked immunosorbent assays (ELISA). For the measurement of CAII, a new ELISA method was developed.

RESULTS AND CONCLUSIONS

The ELISA method was found to be simple, sensitive, economical, and precise. The normal mean levels of erythrocyte CAI and CAII in adults with standard deviation were 13.68 +/- 2.79, and 1.59 +/- 0.21 mg/g Hb, respectively. The corresponding values in cord blood obtained at delivery at 38-40 weeks gestation were 1.20 +/- 0.68 and 0.46 +/- 0.13 mg/g Hb. The mean CAI/CAII ratio in adults was 8.8 and, in newborns, it was 2.5. The normal mean fetal erythrocyte CAI concentration increased significantly with gestation from 39 microgram/g Hb at 20 weeks to 380 microgram/g Hb at 38 weeks of gestation. Similarly, the CAII concentration increased from 53 microgram/g Hb at 20 weeks to 120 microgram/g Hb at 38 weeks of gestation. The CAI to CAII ratio also increased with gestation from 0.9 at 20 weeks to 2.5 at 38 weeks.

A single-step solid phase radioimmunoassay for quantifying human carbonic anhydrase I and II in cerebrospinal fluid

A single-step solid phase radioimmunoassay was developed to detect human carbonic anhydrase (CA) isoenzymes I (CA I) and II (CA II) in cerebrospinal fluid (CSF). The assay is capable of routinely detecting both isoenzymes at ng levels compared to the microgram levels of the traditional catalytic methods, which failed to demonstrate any CA activity in CSF. When the values of immunoreactive CA II in CSF were corrected for blood contamination (the CA I/CA II ratio of blood was about 7.9), the amount of brain tissue originated CA II could be calculated. The CA II values in CSF samples from 13 patients with multiple sclerosis were higher than those in CSF samples from 11 patients with various peripheral neurological disorders. Since CA II has been specifically localized to oligodendrocytes and myelin, our preliminary results suggest the possibility of CA II leakage from oligodendrocytes and myelin into CSF in demyelinating disease.

The measurement of human erythrocyte carbonic anhydrase I by the enzyme linked immunosorbent assay (ELISA)

A method is described for the assay of human erythrocyte (RBC) carbonic anhydrase I (HCAI) by the enzyme linked immunosorbent assay. The method was found to be a simple, reliable and precise technique and gave a mean C.V. for 40 samples, assayed in quadruplicate, of 3.32% and a range of 0.84-5.9. The mean erythrocyte HCAI value and standard deviation for 20 normal men and women were respectively 16.9 +/- 3.4 and 15.4 +/- 2.1 mg HCAI/g haemoglobin. The use of heparin as an anticoagulant interfered with the assay resulting in apparent HCAI concentrations as low as 60% of those obtained using EDTA.

A radioimmunosorbent technique for the assay of B- and C-types of carbonic anhydrase in human tissues

A radioimmunosorbent technique for the assay of the human carbonic anhydrase isoenzymes HCA B and HCA C in tissue fluids was developed. The sensitivity of the method was 0.2 ng/ml and the precision was 5% in duplicate determinations for both enzymes. The presence in a tissue of up to 20 times higher concentrations of one isoenzyme will not interfere with the assay of the other. Haemolysates contained (mean +/- SE, n = 11) 12.1 +/- 0.52 and 1.5 +/- 0.06 mg enzyme/g Hb, and serum 0.63 +/- 0.12 and 0.2 +/- 0.02 microgram/ml of HCA B and HCA C, respectively. Pilot experiments indicated that the isoenzymes can be determined also in tissues, i.e. urine, saliva and cerebrospinal fluid, where catalytic methods previously have indicated absence of or only weak carbonic anhydrase activity. N-terminals of both enzymes were not antigenic.

[Radioimmunoassay of carbonic anhydrase I and II in rats. Application to the central nervous system during ontogeny]

A specific radioimmunoassay method for rat erythrocyte carbonic anhydrases I and II was developed using a double antibody system. Its sensitivity was in the nanogram range for each of the two isozymes. The method has been applied to the assay of cerebral carbonic anhydrase. Only CAII has been found in brain extracts of perfused rats. Accordingly, the assay of CAI in cerebral tissue can be used to quantify erythrocyte contamination on condition that the ratio CAII/CAI in blood had been worked out. The developmental change in the soluble and the Triton X-100 solubilized brain CAII from birth to adult is reported.