Abstract
Ionized calcium has been determined with a new improved instrument on serum samples from 111 Swedish red-and-white cows. Simultaneous sampling of plasma and serum was performed in 32 cows for comparison of the ionized calcium level. Multiple sampling of plasma and serum from seven cows was performed to evaluate the effect of storage at 4°C and room temperature.
The normal range for ionized calcium found in this study implies that the ionized calcium fraction comprises for 43.4 ± 3.0 % (mean ± 2 s) of the total serum calcium. Simultaneous analyses on plasma and serum revealed that the plasma level of ionized calcium was generally 0.ι05 mιmol/1 lower than the serum value. pH changes in stored blood samples have a direct effect on the ionized calcium levels and is therefore to be avoided. Storing samples in vacutainers for five days at 4°C or for two days at room temperature was accompanied by only small decreases of serum or plasma ionized calcium.
The new instrument used in this study enables rapid analyses, and most of earlier drawbacks with calcium-ion-selective analyzers have been eliminated.
Keywords: cow, Swedish red and white breed, ion-specific electrode, ionized calcium, total calcium, differ-ence between plasma and serum, pH effect, effect of storage
Sammendrag
Hos 111 SRB kor bestämdes fritt calcium i serum med en ny förblittrad calcium-jon-selektiv elektrod (Orion Model SS-2u). Hos 32 av dessa togs prov för samtidi·g plasma- och serumbestämning av fritt calcium. Hos 7 av djuren utvärderades effekten av Ja.gring av plasma och serum i såväl 4 °C som i rumstemperatur.
Referensområdet för joniserat calcium definierat i denna studie stämde väl överens med i litteraturen tidigaire angivna data. Joniserat calcium visade sig omfatta 43,4 ± 3,0 % (± 2 s) av total calcium. Analys av joniserat calcium i plasma och serum visade 0,05 mmol/l lägre värden i plasma än i serum. pH-förändringar i lagrat prov har en direkt effekt på joniserat calcium och bör därför undvikas. Vi fann det möjligt att lagra prover under åtminstone 5 dagar vid 4. °C eller under åtminstone 2 dagar i rumstemperatur utan medföljande påtagliga förändringar av haiten joniserat calcium.
Vi fann att det här använda instrumentet gav klart bättre möjlighet till snabba och mer tillförlitliga analyser utan de stora metodologiska svårigheter som varit förenade med tidigare använda metoder.
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