Metabolism of DL-1,2-Propanediol-2-14C in a Lactating Cow

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Abstract
Since propanediol is glucogenic and is extensively used in therapy of bovine ketosis, its metabolic fate was investigated. DL-1,2-propanediol-2-14C with 400 g of carrier propanediol was administered intraruminally to a lactating cow. During the next 24 hours, the percentage of the dose recovered was 43.7 in CO2, 12.4 in milk, 3.5 to 7 in urine, and less than 0.1 in feces. The propanediol was predominantly absorbed from the rumen without alteration, although some conversion to propionic acid in the rumen was detected. The maximal level of propanediol in milk was 0.04 mg/ml. Distribution of 14C among the carbons of lactose and glutamic acid indicated conversion of propanediol to glucose via carboxylation of pyruvate to oxalacetate. These results demonstrate that propanediol is glucogenic in the classical sense of that term; namely, that it is metabolized via intermediates, probably pyruvate and oxalacetate, which can lead to net synthesis of glucose. The small concentrations of propanediol in peripheral blood and the approximately 2-hour delay in attaining maximal specific activity in CO2 after attaining maximal specific activity of blood glucose indicated that glucogenesis was primarily hepatic with oxidation primarily occurring in other tissues.