The Uptake of L-Lactate and D-Glucose by the Mammary Gland of the Cow

Abstract

Although the uptake oflarge amounts of blood glucose by the lactating mammary gland of the ruminant is well documented, there are conflicting reports on the uptake of lactate. Graham (1937) reported a mean uptake of lactate of 16·7 mgj100 ml blood by the mammary gland of goats in which the arterial concentration of lactate was unusually high. A considerably smaller uptake was found in unanaesthetized cows (Shaw, Boyd, and Petersen 1938) but the results of subsequent studies on anaesthetized cows (Shaw 1946) indicated that the mammary gland did not utilize a significant amount of blood lactate.It has been estimated that, in sheep, at least 40% of the lactate pool is derived from glucose and a minimum of 15% of the glucose pool is derived from lactate (Annison, Lindsay, and White 1963). If a similar interconversion occurs in the cow, the net uptake ofL-lactate should be considered in assessing the net uptake ofD-glucose. This communication describes studies carried out on lactating cows to determine the arteriovenous difference for L-lactate across the mammary gland. An attempt also has been made to relate the uptake of L-lactate to that of D-glucose.