Apparent volumes of distribution of 125-I-lothalamate and inulin in chickens.
The suitability of utilizing 125-I-iothalamate to estimate the volume of extracellular fluid was assessed in ureterally ligated chickens. Subsequent to intravenous administration the movement of labeled iothalamate from the plasma compartment follows closed two-compartment kinetics and equilibration between vascular and extravascular phases is attained in about 20 minutes. The volume of distribution of 125-I-iothalamate prior to and following the influsion of 0.15 M NaCl (equal to 15% of the estimated ECFV) averaged 23.6 plus or minus 0.61 and 28.4 plus or minus 0.22% of the body weight, respectively. The observed postsaline labeled iothalamate space did not differ statistically from the expected value. When administered simultaneously inulin penetrates into an apparent volume that is 75% of the labeled iothalamate space after 60 minutes. The content of 125-I-iothalamate is relatively high in liver and kidney tissue and suggests that these are major sites where removal of the indicator from plasma occur. It is suggested that 125-I-iothalamate, under appropriate conditions, could be used to measure the plasma volume and the extravascular fluid with which plasma is in rapid diffusion equilibrium.
D000818:Animals; D001835:Body Weight; D002642:Chick Embryo; D002645:Chickens; D005110:Extracellular Space; D006801:Humans; D007231:Infant, Newborn; D007275:Injections, Intravenous; D007444:Inulin / Q000378:metabolism*; D007457:Iodine Radioisotopes; D007483:Iothalamic Acid / Q000097:blood / Q000378:metabolism*; D007668:Kidney / Q000032:analysis; D007700:Kinetics; D008026:Ligation; D008099:Liver / Q000032:analysis; D009206:Myocardium / Q000032:analysis; D010424:Pentobarbital / Q000008:administration & dosage; D012965:Sodium Chloride / Q000378:metabolism; D013997:Time Factors; D014513:Ureter
D007457:Iodine Radioisotopes; D007483:Iothalamic Acid; D012965:Sodium Chloride; D007444:Inulin; D010424:Pentobarbital