C. L. Comar

Metabolism of Gr51 by Animals as Influenced by Chemical State.

Summary The physiological behavior of trivalent and hexavalent Cr51 has been observed over a 4 5-day period in rats as affected by chemical form and route of administration. When intravenously administered as sodium chromite, practically 100% of the dose was picked up by the organs of the reticuloendothelial system. Chromic chloride resulted in a pickup by the liver of about 55% of the dose. When Cr51Cl3 was added to isotonic acetate and citrate buffers; less than 5% of the dose reached the liver and most of the activity was excreted in the urine. The use of sodium chromate solutions resulted in about 25% of the dose reaching the liver. However, the activity left this organ rapidly in contradistinction to the other forms studied. Oral, intraperitoneal and intratracheal administration of Cr51Cl3 were also studied. None of the forms of Cr51 used were found to cross the placenta of rats ranging from 15 to 20 days in gestation. In addition, data are presented from 2 sheep intravenously dosed with Cr51Cl3. The above physiological observations are correlated with the colloidal behavior, complex formation, protein binding, and red cell binding, and are in general agreement with interpretations of filter paper elec-trophoretic studies of the dosing solutions.

Blood Volume of Swine.

Summary The P32 labeled red blood cell method has proven satisfactory for the determination of blood volumes in swine. Values obtained ranged in regular fashion from 7.4 to 4.6 ml/100 g body weight for 10 to 344 lb animals^ respectively.

Copper, molybendum and zinc interrelationships in rats and swine.

Summary and Conclusions Substantial increases in tissue copper concentrations and radiocopper accumulation resulted when a: level of 1000 p.p.m. of molybdenum as sodium molybdate was fed to rats and swine on a natural ration. This increase was especially pronounced in the kidneys and livers and is in accord with the hypothesis that excess copper, which is not physiologically effective, may be accumulated when a high level of molybdenum is fed. A dietary level of 1000 p.p.m. of zinc did not appear to have any appreciable effect upon copper metabolism. Growth depression in rats produced by 1000 p.p.m. of added molybdenum to a natural or synthetic ration was not counteracted by the addition of 200 p.p.m. dietary copper. Swine appeared to be more resistant to molybdenum toxicity than did rats. No degenerative changes were observed in the spinal cord, leg joints or muscle tissues of swine fed levels of 1000 p.p.m. of molybdenum or 1000 p.p.m. zinc for a 7-month experimental period. With the criteria of these experiments it appears that dietary zinc was not involved in copper-molybdenum imbalance.

Effect of calcium status, mass of calcium administered and age on Ca45 metabolism in the rat.

Summary (1) The fecal excretion of orally administered Ca45 is a sensitive indication of the calcium status of the rat; (2) placing normal rats on a low calcium diet for as little as 2 days greatly increased their ability to absorb Ca45 from the tract; (3) the specific activity of labeled calcium at the site of absorption had little effect upon its absorption; (4) in general, younger rats absorbed more Ca45 than did older ones although there was no significant difference between 6 1/2 and 16-month-old animals; (5) for meaningful studies of this type, interpretations must include consideration of exchange reactions, and care must be given to initial selection of diets and animals, preparation of animals for the experiment, and dietary management during the experimental period.

Vitamin B12 Biosynthesis after Oral and Intravenous Administration of Inorganic Co60 to Sheep.

Summary 1. Excretions and tissues from wether lambs dosed orally and intravenously with inorganic cobalt-60 were measured for total radioactivity and also for radioactivity in fractions characterized chemically as vit. B12-like, inorganic and bound. 2. After oral administration there was considerable biosynthesis of vit. B12 in the tract, probably occurring mainly in the rumen. After intravenous administration there was only slight, if any, biosynthesis in the tract, but considerable formation of vit. B12 in the tissues with the suggestion that the adrenals and spleen were mainly responsible. Overall, there was more than 10 times as much Co60 converted to B12 after ingestion than after intravenous administration. 3. The concentrations of vit. B12-like Co60 in the tissues after intravenous injection were slightly higher than after ingestion of equal amounts of Co60. 4. In the light of results on the response of cobalt-deficient lambs to parenterally administered vit. B12, it is suggested that the vit. B12-like material synthesized by the tissues from inorganic cobalt is physiologically ineffective in relieving cobalt-deficiency symptoms in sheep.

Effect of Parathyroid Extract Administration in Sheep.

Summary The effect of parathyroid extract and administration upon the removal of radiocalcium and radiophosphorus from the long bones of sheep and its subsequent excretion in the urine was studied. Over a 5-day period of treatment, radiophosphorus but not radiocalcium was removed from the bone. The parathyroid extract produced only a slight rise in the urinary excretion which may be accounted for by the elevated serum phosphorus. Daily doses of 1000 i.u. of parathyroid extract over a 7-day period resulted in elevation of the serum phosphorus levels but not of serum calcium. It is concluded that in the sheep, parathyroid extract acted directly upon the bone and that any effect upon the kidney was minor in the dosage range and time periods employed; also, it appeared that phosphorus metabolism was much more influenced than was calcium metabolism.