Abstract
From previous studies measuring ultrafilterable Ca, it was felt that increasing P concentration would lead to a decrease in iCa, due to P binding to iCa. Since no specific studies measured directly iCa as a function of P, we examined the effect of P on iCa concentration in vitro. We hypothesized that within the range of clinically encountered pH an increase in serum P would lead to a decrease in iCa. A single donor serum was aliquoted into 25 samples stored in CO2 sealed tubes, and divided into 5 subsets of 5 tubes. pH was altered in 4 of the 5 subsets by adding various concentration of HCL or of NaOH. The pH's studied were: 7.09, 7.28, 7.35, 7.51, and 7.63. P concentration was altered in each subset by adding various concentrations of a P buffer with a pH of 7.4. The P concentrations studied were 2.5, 4.6, 6.8, 8.3, 11.1 mg/dl. iCa was measured using a Radiometer iCa 1 ion-selective electrode (standard error of measurement: 0.04 mg/dl). There was an inverse relationship between iCa and P which was similar at all pH's studied (r ranging from -0.84 to -0.94, p<0.001). The slopes did not differ significantly from each other, indicating no deviation from parallelism of these 5 regression lines. iCa concentration correlated inversely with pH (p<0.001). There was no significant interaction between P concentration and pH. Therefore iCa concentration in vitro inversely correlates with pH and P concentration. We suggest that in addition to factors well known to influence iCa concentration (such as protein, bicarbonate and pH), serum P concentration also plays a significant role.
Article PDF
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Lehmann, M., Mimouni, F. & Tsang, R. EFFECT OF PHOSPHATE (P) CONCENTRATION ON IONIZED CALCIUM (iCa) CONCENTRATION IN VITRO. Pediatr Res 21 (Suppl 4), 202 (1987). https://doi.org/10.1203/00006450-198704010-00216
Issue Date:
DOI: https://doi.org/10.1203/00006450-198704010-00216