Radioimmunoassay for human aldolase A

Immunochemical and immunohistochemical studies on three aldolase isozymes in human lung cancer

The aldolase isozymes A, B, and C in tumor tissues (63) and sera (104) of patients with lung cancer were determined with an enzyme immunoassay system, compared with normal lung tissues (13), and the sera of normal healthy subjects (100). Tissue aldolase A and C concentrations were enhanced in 83% (52/63) and 51% (32/63) of patients with lung cancer, respectively, regardless of histologic type or stage (P less than 0.01). But aldolase B was not elevated in tissue levels. In the sera of patients with lung cancer, there were no significant elevations of the isozymes. Immunohistochemically aldolase A and C stained more intensely in the cytoplasm of lung cancer cells than those in normal tissues. These results indicate lung cancer cells contain enhanced tissue levels of aldolase A and C.

Sensitive enzyme immunoassay for human aldolase A

A sensitive sandwich-type enzyme immunoassay for the aldolase isozyme, A4, was developed using purified antibodies specific to the A subunit of aldolase. The antibodies were raised in sheep being immunized with purified aldolase A4 and then purified by immunoaffinity chromatography on a column of aldolase A4-coupled Sepharose. The assay system consisted of polystyrene balls with immobilized antibody F(ab')2 fragments and the same antibody F(ab')2 fragments labeled with beta-D-galactosidase from Escherichia coli. The assay was sensitive enough to detect 10 pg/tube of aldolase A4. The assay was specific to the A subunit of aldolase (aldolase A). It cross-reacted about 40% to aldolase A3C, 7% to A2C2 and 0.3% to AC3, but not cross-reacted with C4 nor B4. Coefficients of variation in intra- and inter-assay were less than 16%. Serum aldolase A levels were determined in healthy adults, which were about 200 ng/ml. The distribution and concentrations of immunoreactive aldolase A in various human tissues were also determined. High concentrations of aldolase A were found in skeletal muscle, heart muscle, cerebrum and lymphatic tissue.

Decreased serum aldolase B levels in patients with malignant tumors

Serum aldolase B levels were determined in patients with malignant tumors using a radioimmunoassay method. Thirty-one of 52 patients with malignant tumors had decreased serum aldolase B levels of less than 20 ng/ml, whereas almost all of the normal subjects and the patients with liver diseases and other benign diseases showed serum aldolase B levels of more than 20 ng/ml. The decreased aldolase B levels observed in cancer patients were unrelated to the clinical stage of their disease. The decrease of aldolase B correlated well with the decrease of fructose-1-phosphate (F1P)-aldolase activity, but not with fructose-1,6-diphosphate (FDP)-aldolase activity in the sera of cancer patients. Mixing experiments did not identify an inhibitor of aldolase B in sera of cancer patients. Furthermore, recovery of serum aldolase B levels after successful surgical resection in cancer patients suggested that the low levels of aldolase B in sera of cancer patients was not of genetic origin. The mechanism responsible for the decrease of aldolase B in sera of cancer patients is unclear.

Human aldolase B serum levels: a marker of liver injury

A solid-phase, noncompetitive radioimmunoassay has been developed for aldolase B in human serum and tissues. Aldolase B was purified from human liver, and specific antisera to purified aldolase B were obtained from chickens. Specific antihuman aldolase B IgG was purified by affinity chromatography. Disposable polypropylene plates were coated with affinity purified specific IgG antibody and used for radioimmunoassay with 125I-specific IgG antibody to aldolase B. The nonspecific binding was minimized by saturating the binding sites of the plates with 2% ovalbumin in 0.1% Tween 20. This radioimmunoassay is specific for the aldolase B subunit, with no cross-reactivity with human aldolase A or aldolase C subunits. Aldolase B is predominantly found in normal liver. Relatively high aldolase B levels are also observed in kidney. Serum levels of aldolase B in 21 normal subjects ranged from 21 to 39 ng per ml, with a mean of 28.7 +/- 8.6 (2 S.D.) ng per ml. Forty of 42 (95%) patients with acute and chronic hepatitis without cirrhosis had serum aldolase B levels greater than 40 ng per ml. Serum aldolase B levels correlated well with total serum aldolase enzyme activities (r = 0.967) and SGPT (r = 0.951) in patients with liver diseases. In cancer patients, serum aldolase B was slightly elevated in 15 of 26 (58%) patients with cancer metastatic to the liver or primary liver cell carcinoma, whereas no elevation of serum aldolase B was observed in 16 cancer patients without liver metastasis. Measurements of aldolase B serum levels by radioimmunoassay appear to be a useful measure of liver cell necrosis from benign or malignant liver diseases.

Subunit-specific radioimmunoassay for aldolase A, B, and C subunits: clinical significance

Radioimmunoassays specific for fructose-1, 6-diphosphate aldolase isozymes were developed for the quantification of human aldolase A, B and C. The method is a double-antibody radioimmunoassay using radioiodinated purified aldolase A, B and C as ligand, chicken antibodies to aldolase A, B and C, and rabbit antibodies to chicken IgG. The Iodogen method was used for the iodination of aldolase A, B and C in this study. Aldolase A was predominantly high in concentration in muscle, aldolase B was high in normal adult liver, and aldolase C was high in adult brain. Aldolase A was elevated in hepatoma tissue and hepatoma cell lines, where aldolase B was distinctly low. Normal serum levels for the three isozymes were determined. The aldolase A levels in serum obtained from 41 normal subjects were 170 +/- 39 ng/ml. Serum aldolase A levels were increased in many patients with cancer and muscle diseases, but were not increased in patients with hepatitis or other benign diseases. Serum aldolase B levels obtained from 11 normal subjects were 28.5 +/- 9.2 ng/ml. Serum aldolase B levels were increased in patients with hepatitis and correlated well with serum GPT levels. Serum aldolase C levels obtained from 12 normal subjects were 2.4 +/- 0.7 ng/ml. The determination of aldolase A, B and C by radioimmunoassay may be a valuable tool in biochemical and clinical studies of aldolase isozymes.

Radioimmunoassay of aldolase A. Determination of normal serum levels and increased serum concentration in cancer patients

A radioimmunoassay specific for human aldolase A subunits was used to measure human aldolase A (ALD-A) in human serum. The double antibody competitive inhibition radioimmunoassay technique used radioiodinated purified ALD-A as ligand, chicken antisera specific for human ALD-A and rabbit antichicken IgG. The serum levels of ALD-A in 42 normal healthy subjects ranged from 130 to 210 ng/ml (mean average, 171 +/- 39 ng/ml). In 177 hospitalized patients without cancer, muscle diseases, or hemolytic anemia, the ALD-A serum levels ranged from 125 to 220 ng/ml. In contrast, 82% of 260 patients with various types of malignancy had ALD-A serum concentrations above the normal range. The CEA levels increased only 44% of the sera of 80 patients with cancer of the digestive tract, whereas the ALD-A levels were increased in 86% of the patients. The AFP levels were greater than 100 ng/ml in only 70% of the sera of 33 liver cell carcinoma patients, whereas the ALD-A levels were increased in 94% of these sera. The measurement of serum ALD-A by radioimmunoassay may be a valuable adjunct in the clinical diagnosis of certain cancer patients.

A non-competitive solid-phase radioimmunoassay for human aldolase A

A solid-phase, non-competitive radioimmunoassay for aldolase A in human serum has been developed. Human aldolase A was purified from muscle, and specific antisera to the purified aldolase A were obtained from chickens. Specific IgG anti-human aldolase A was purified by affinity chromatography. Disposable polypropylene plates were coated with specific IgG antibody and used for radioimmunoassay with 125I-specific IgG antibody to aldolase A. The non-specific binding was minimized by saturating the binding sites of the plates with 2% ovalbumin in 0.1% Tween 20. This radioimmunoassay is specific for the aldolase A subunit, with no cross-reactivity with human aldolase B subunit or homopolymeric human aldolase C(C4). The serum aldolase A immunoreactivities of 33 normal subjects ranged from 124 to 212 ng/ml with a mean of 178 +/- 41 ng/ml (+/- 2 SD). Ninety-three patients' sera were assayed with both a solid-phase non-competitive radioimmunoassay and a competitive double antibody radioimmunoassay developed in our laboratory and the results showed a high degree of correlation (r = 0.912; p less than 0.001). Rapidity and simplicity of the solid-phase assay makes it superior to other methods for the measurement of serum aldolase isozymes.