Excretion of Tritium labeled prednisolone in clinically normal and experimentally infected bovine udders

Geleta, J.N.; Shimoda, W.; Mercer, H.D.

American Journal of Veterinary Research 45(8): 1576-1581


The excretion rate of [3H]prednisolone from clinically normal and experimentally infected udders of 10 lactating cows was studied. Each quarter of 6 cows was injected with a single dose of [3H]prednisolone mixed with nonradioactive prednisolone equivalent to 10 mg in 10 ml of peanut oil base. Each of the remaining 4 cows was given 40 mg of nonradioactive prednisolone and [3H]prednisolone in 60% ethanol IV. Control and postadministration samples of blood, milk, and urine were examined for radioactivity. The effects of [3H]prednisolone were evaluated in the same cows, first in clinically normal udders, then 2 wk later in udders experimentally infected with Streptococcus agalactiae. Absorption and elimination of prednisolone were the same before and after induced infection. Within 3 h after intramammary injection, 95% of the labeled prednisolone was absorbed systemically, < 5% of this dose was recovered win milk, and 29% was excreted in urine. After i.v. injection of [3H]prednisolone, < 0.2% of the total radioacivity was recovered in milk and < 46% was excreted in urine. Clinical mastitis induced by S. agalactiae was moderate. Circulating blood leukocytes and somatic cells in the milk of normal cows remained essentially unchanged. The leukocyte response to induced infection was rapid in blood and milk. Large numbers of leukocytes were noticed in the milk and a severe leukopenia occurred. Prednisolone treatment did not alter the number of somatic cells in milk or reduce the inflammatory response of experimentally infected cows.