[Measurement of circulating 1,25-dihydroxyvitamin D employing radioimmunoassay].

Measurement of serum 1,25-dihydroxyvitamin D levels is important for diagnosis of various calcium metabolism disorders. Conventional assays for 1,25-dihydroxyvitamin D employed specific 1,25-dihydroxyvitamin D receptor as binding site for the ligand and thus, biologically active 1,25-dihydroxyvitamin D ligand, which is labeled with 3H, was required. Usage of 3H made assays cumbersome works. A new assay which uses specific antibody as the binding site and the radioligand labeled with 125I is now available as a commercial kit. Using these kits, we first studied basically the reproducibility, recovery, cross-reactivity and comparison with conventional assays. All of those results were satisfactory. Secondly, we measured clinically in 111 healthy adults and in patients with various disorders such as renal failure, primary hyperparathyroidism, hypoparathyroidism and sarcoidosis. This newly available kit for measurement of circulating 1,25-dihydroxyvitamin D is proved to be useful in clinical evaluation of calcium metabolic disorders.

[Radioimmunoassay for the pyridinoline cross-linked carboxy-terminal telopeptide of type 1 collagen (1CTP)--some basic aspects of the RIA kit and clinical evaluation in various bone diseases].

A radioimmunoassay for circulating levels of the pyridinoline cross-linked carboxy-terminal telopeptide of type 1 collagen (1CTP) was developed and can be available as a kit on a commercial base. Using the kits, we evaluated basically and clinically the assay. The assayed values were reproducible and the assay can detect as low as 0.5 ng/ml of 1CTP. In healthy volunteers, circulating level was high under age 24 and over age 46. In patients with bone metastasis, serum levels elevated even in its early stage and correlated well with clinical status. In other bone diseases, such as primary hyperparathyroidism, hyperthyroidism, post-gastrectomy, hypercalcemia of malignancy and myeloma, serum levels elevated according to their clinical conditions. In patients with chronic renal failure, serum levels were high, suggesting decrease of renal clearance of 1CTP. The circulating 1CTP levels seemed to reflect well clinical bone destructive status. A high correlation between serum 1CTP level and urinary pyridinoline (r = 0.884) was shown, whereas essentially no correlation was observed between bone formation markers such as osteocalcin and alkaline phosphatase. Thus, the measurement of circulating 1CTP seems to be a simple and sensitive method to monitor bone destruction.

[Measurement of serum concentration with radioimmunoassay for carboxyterminal propeptide of type 1 procollagen].

A radioimmunoassay kit for measurement of carboxyterminal propeptide of type 1 procollagen (P1CP) was developed and can be purchased commercially for clinical use. Using the kit, we measured serum concentration in healthy controls and in patients with bone metastasis and other various skeletal disorders. In healthy controls, serum concentration of P1CP ranged within 37-177 ng/ml under age 50, while in serum concentration of women over 50, it elevated upto 350 ng/ml. In patients with skeletal metastasis, in most of patients, it stayed within a normal range, whereas in patients with bone metastasis from prostatic cancer, it raised significantly. In some of patients with primary hyperparathyroidism or hyperthyroidism, serum concentration for P1CP was also elevated. In comparison with other serum bone metabolic markers such as osteocalcin or alkaline phosphatase, P1CP showed less occurrence of an elevation in patients with non-skeletal disease. Serum concentration of P1CP was not affected by renal function, while mild elevation was observed in patients with severely damaged liver diseases. In conclusion, the newly developed radioimmunoassay for P1CP was an excellent assay system and would provide us easily evaluation of type 1 collagen formation.