Methodological errors in radioisotope flux measurements.
We examined several sources of error in isotopic flux measurements in a commonly used experimental model: the study of 22Na and 36Cl fluxes across rat ileal tissue mounted in the Ussing flux chamber. The experiment revealed three important sources of error: the absolute counts per minute, the difference in counts per minute between serial samples, and averaging of serial samples. By computer manipulation, we then applied hypothetical changes in the experimental protocol to generalize these findings and assess the effect and interaction of the absolute counts per minute, the sampling interval, and the counting time on the magnitude of the error. We found that the error of a flux measurement will vary inversely with the counting time and the difference between the consecutive sample counts per minute used in the flux calculations and will vary directly with the absolute counts per minute of each sample. Alteration of the "hot" side specific activity, the surface area of the tissue across which flux is measured and the sample volume have a smaller impact on measurement error. Experimental protocols should be designed with these methodological considerations in mind to minimize the error inherent in measuring isotope flux.
Egnor
R W
RW
Nephrology Section, Veterans Administration Medical Center, New York, New York.
Vaccarezza
S G
SG
Charney
A N
AN
D000818:Animals; D003951:Diagnostic Errors; D003947:Diagnostic Techniques, Radioisotope / Q000379:methods*; D008297:Male; D010827:Physiology / Q000379:methods*; D051381:Rats; D011919:Rats, Inbred Strains