AJP - Gastrointestinal and Liver Physiology, Vol 245, Issue 3 438-G441, Copyright © 1983 by American Physiological Society
A new technique for measuring intestinal calcium absorption in the rat
C. L. Marsh, A. D. LeBlanc, P. C. Johnson and S. L. Pool
A double-isotope technique that does not necessitate urine and fecal
collections but requires only the extraction of the incisor teeth for
isotopic analysis has been devised. A precalibrated dose of 45Ca in
solution with stable carrier calcium is administered to the rat orally. An
intraperitoneal injection delivers a precalibrated dose of 47Ca in isotonic
saline. The ratio of the percentage uptake of the two radionuclides in the
incisor tooth is equal to the fraction of the 45Ca and, therefore, the
calcium absorbed by the gut. The fraction of calcium absorbed by 5-mo-old
rats, as determined by collection and measurement of excreta, was found to
be 39.1%. The ratio of uptake of the two calcium radionuclides in the
incisor teeth yields an absorption measurement of 38.8%, nonsignificantly
different from the value obtained from the excretion data. The measurement
of radiocalcium uptake in the incisor tooth affords one an accurate in vivo
determination of intestinal calcium absorption without the collection of
excreta or multiple blood sampling.
