engleski

Estimation of radioactive calcium absorption based on expanding Ca-exchangeable space

Anthropological interest in calcium metabolism is partially connected with the genetic basis of skeletal metabolism that could provide additional optimism for people suffering from osteoporosis. The present investigation is aimed at deal with a of model describing Ca intestinal absorption, suitable for other descriptions currently investigated in anthropology (migration and gene flow). The purpose of this investigation was to establish features of the reflection of the Ca isotopic absorption tests in serum using the concept of an expanding Ca-space and to assess the reliability of the estimation of absorption (ABS) from one serum sample.Double tracer method, using 85Sr as the iv tracer, was used as the referent. The study included 100 subjects (49 females, 51 males) of which 34 were considered healthy. The mean value of ABS was 68 (ą17.45 SD) % of dose. Serum radioactivity during the 24 hours following oral administration of 47Ca (together with 100 mg elemental Ca), o.s(t), from five blood samples was determined. The relationship between o.s(t) and ABS was found to be connected to an expanding Ca space, V(t): ABS= o.s(t)V(t)=26+11.8t0.35 o.s(t) After the absorption process was finished, an approximate value of V(t) is (100/S1)(t-x)b. The constants "S1" and "b" describe power function of iv s(t), whereas parameter "x" represents delay of V(t) Ca-space at oral administration in comparison to the iv administration. Statistical models selected on the basis of their low values of the SEE (from 8.71 to 8.90 % of dose) include body surface index or body weight index (BW0.425). The CV expressed as (SEE/mean ABS(Ca/Sr) )100 were about 13% and the observed greatest difference between the estimated and measured ABS(Ca/Sr) was 20% of dose.The authors believe that models presented permit, to a limited extent, comparison of results obtained by different procedures. The results, according to variability of the sample of subjects, permit judgment on upper limits of error at estimation of absorption from one blood sample radioactivity.

radioactive calcium; Ca-exchangeable space; population genetics; anthropology

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