The Partition of Calcium and Protein in the Blood of Oviparous Vertebrates during Estrus

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Abstract
Six classes of vertebrate animals were injected with massive doses of estrogen for various periods of time necessary to produce a grossly recognizable response. Swelling of the liver, associated with hypercalcemia, hyperproteinemia, and lipemia, occurred in Teleostei, Amphibia, Reptilia, and Aves, but not in Elasmobranchii or Mammalia. Calcium that was added to the serum was bound as a calcium proteinate complex, synthesized in the liver, and liberated into the plasma. The concentration of calcium per gram was considerably higher than in other oviparous animals. Teleostei, Amphibia, and Reptilia, produced one new component, protein-X1, having a sedimentation constant of approximately 17S, and many properties of a protein previously described in birds as X2. Calcium-binding capacity of teleostean and amphibian serum proteins was estimated at 25 to 35 mg. per gm. of the mixed proteins of the serum; reptilian serum proteins bound 55 mg. per gm. Estrogen-treated birds clearly produced two, rather than one, new proteins, a phosphoprotein, X1, having a rate of 8.5S, and X2, a phospholipid-lipoglycoprotein, 17S. The calcium-binding capacity was approximately 50 mg. per gm. of the mixed proteins of the serums. Circumstantial evidence suggests that the plasma proteins of oviparity appeared simultaneously with the evolution of bone as a tissue and an ultimobranchial gland having parathyroid function.