LACTATE PRODUCTION AND LACTATE DEHYDROGENASE IN HUMAN EPIDERMIS

[摘要] Experiments using slices of epidermis floating on tissue culture media containing glucose demonstrate a production of lactate which is 100 times less than the maximal measurable rate of lactate production in epidermal homogenates. The epidermal slice with its intact cellular organization is presumably close to the in vivo situation and therefore implies that in vivo lactate dehydrogenase is inhibited to the point where only about 1% of Its maximal activity is being utilized, Measurements of the in vivo concentrations of the substrates and products of the LDH reaction demonstrate that the inhibition of LDH activity in vivo cannot be due to a lack of Substrates or an excess of products within the cell. Furthermore, no inhibitors of this reaction are demonstrable within the epidermal homogenate. It is concluded that the inhibition of LDH activity within the cell must be due to the facts of cellular organization; that although substrate concentrations within the cell are adequate, these substrates are prevented from gaining access to the LDH and are therefore in effect in very low concentration at the active site of the enzyme.