Purification of swine carbonic anhydrase isoenzyme III and measurement of its levels in tissues and plasma

The changes in the levels of carbonic anhydrase isozyme III (CA‐III) in swine plasma and urine have not been previously determined or reported. CA‐III is relatively specific to skeletal muscles, and should therefore be a useful diagnostic marker for muscle diseases. We isolated CA‐III from swine muscle tissues and determined CA‐III levels in the plasma and urine from both healthy and diseased pigs. The levels of CA‐III in the tissues of female swine (age, 3 months) and plasma of young swine (age, 1–5 months) and adult female pigs (age, 2–3 years) were determined using the ELISA system for swine CA‐III. The mean (± SD) levels of CA‐III in the skeletal muscles were 3.8 ± 3.2 mg/g (wet tissue), and in the plasma, 230 ± 193 ng/ml at 1 month, 189 ± 208 ng/ml at 2 months, 141 ± 148 ng/ml at 3 months, 78 ± 142 ng/ml at 4 months and 53 ± 99 ng/ml at 5 months. The mean level of CA‐III in the plasma samples from 2‐ to 3‐year‐old pigs was 18 ± 60 ng/ml. CA‐III in the plasma samples was found to decrease from 1 month until 3 years of age (p < 0.01). We performed far‐western blotting to clarify the cause of the observed decrease in CA‐III in plasma. Our results demonstrated that CA‐III is bound to the transferrin and albumin. In addition, we determined that the levels of CA‐III in plasma and urine samples were higher in diseased swine compared with the healthy pigs.