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KINETICS OF RAPID 45 Ca UPTAKE INTO CHICK SKELETON IN VIVO : EFFECTS OF MICROWAVE FIXATION
Author(s) -
Shaw A. J.,
Whittaker G.,
Dacke C. G.
Publication year - 1989
Publication title -
quarterly journal of experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0144-8757
DOI - 10.1113/expphysiol.1989.sp003361
Subject(s) - fixation (population genetics) , in vivo , isotope , skeleton (computer programming) , femur , chemistry , anatomy , andrology , biology , surgery , medicine , biochemistry , physics , microbiology and biotechnology , quantum mechanics , gene
We have investigated uptake kinetics for 45 Ca labels acutely administered as single intravenous injections into twelve‐day‐old chicks in vivo. Effects of microwave fixation on this process have aJlso been studied. Rapid uptake of 45 Ca was demonstrated into the skeleton with approximately 40% of injected label being found in the skeleton within the first 15 min. By 45 min tissue 45 Ca levels had stabilized and showed little change during the following 90 min. Soft tissue isotope levels declined during the period from 3 to 135 min following injection. These data were obtained from animals in which tissue isotope levels were stabilized by fixation with microwaves at the point of killing by cervical dislocation. In animals where the microwave fixation step was omitted and tissues were dissected for counting at least 1 h after killing, 45 Ca levels in both skeletal and soft tissues were 15‐20 % higher than in those from microwaved groups during the period 3‐15 min after injection. In a separate experiment, groups of chicks killed by cervical dislocation 3 min after isotope injection were fixed with microwaves at time intervals ranging from 0 to 45 min post‐mortem . Isotope levels in femur increased with time and were significantly higher in groups in which fixation was carried out 12 and 45 min after death when compared with those fixed at the point of death. Data in calvarium reflected those in femur but were not statistically significant at the time intervals tested. Estimates of unidirectional plasma‐bone Ca 2+ influx ( J Pb 40 Ca) into chick bone indicate high values for femur, 〉 1·64, µmol min‐1 (g wet weight) −1 and calvarium, 〉 1·26 µmol min −1 (g wet weight) −1 , respectively. This suggests that Ca 2+ is cleared very rapidly between blood plasma and exchangeable pools in the skeleton of the chick. Estimated J Pb 40 Ca values decline appreciably over short (15 min) time intervals, suggesting that significant backflux of the 45 Ca marker occurs. These data collectively indicate that uptake of 45 Ca into skeletal tissues occurs rapidly following its injection into chicks. 45 Ca uptake continues for several minutes in the immediately post‐mortem animal and this process is reduced by microwave fixation. It is important to bear these factors in mind, when considering the effects of hormones and drugs on the uptake of bone‐seeking radionuclides.