Cobalt Polycythemia in the Dog

Abstract

The hematopoietic power of cobalt was first demonstrated on the rat by Waltner. 1 Orten and coworkers 2 , 3 , 4 have shown that a daily dose of 0.5 mg. cobalt, with copper and iron, produces in rats a true polycythemia involving an increase of the blood volume, and that cobalt probably acts by stimulating the hematopoietic organs. Kleinberg 5 reported that the subcutaneous injection of cobalt chloride produces in rabbits a polycythemia, and an increased reticulocyte percentage. Mascherpa 6 reported that the oral administration of cobalt to dogs produces an increased erythrocyte number. Brewer, 7 however, reported that the daily feeding of cobalt chloride in doses of 0.8 to 4 mg. of cobalt per kg. failed to produce a significant polycythemia in his dogs. He asserts that the erythrocyte number in normal dogs may vary by 15 to 20% as observed on consecutive days.

In view of these conflicting reports on the effect of cobalt upon the erythrocyte number of the dog, I decided to reinvestigate the question.

Four dogs used in this investigation were fed a uniform daily diet of Purina dog chow. Two of these dogs were normal females, while the other 2 (males) were polycythemic due to the fact that they had finished a prolonged period of daily treadmill running just 3 weeks before the cobalt feeding was commenced.

Cobalt was administered in the form of cobaltous chloride in 1:1000 solution (cobalt equivalent) by stomach tube each day just before feeding. It was found that the salt could not be given in gelatin capsules, as this form of administration caused the dogs to vomit. During the first period of cobalt feeding, 2 of the dogs were given 2 mg. cobalt per kg. daily, while the other 2 were given 6 mg. After 3 weeks the cobalt was discontinued for about 3 weeks, then all 4 dogs were given a uniform dose of 2 mg. cobalt per kg. daily over a period of about 2 weeks.