C¹⁴-labeled glucose metabolism by bone from normal and parathyroid-treated rats

¹ Department of Biochemistry, Northwestern University Medical School, Chicago, Illinois

Calvaria and the metaphyseal and epiphyseal sections of tibia and femora freed of bone marrow from young growing rats were incubated in vitro for 2 hr at 37 C in Krebs-Ringer bicarbonate buffer containing 2 mm glucose. The glucose was labeled either in the 1 position or in the 6 position or uniformly in all positions with C¹⁴. The incorporation of C¹⁴ into citrate, lactate, and various tricarboxylic acid cycle intermediates was studied. The release of C¹⁴O₂ and the incorporation of C¹⁴ into bone matrix were also measured. Results obtained from bones of untreated control, parathyroid extract-treated, and parathyroidectomized animals were compared. It was found that treatment of animals with parathyroid extract increased the total accumulation of labeled citrate and malate as well as the incorporation of these acids into bone mineral. Bones from extract-treated animals also exhibited a significant decrease in the total accumulation of radioactive fumarate, succinate, and pyruvate. Lactate was the major end product of glucose metabolism, but its accumulation was only slightly influenced by parathyroid extract.

Key Words: citrate in bone • lactate production by bone • matrix of bone • mineral fraction of bone • pentose cycle in bone • Krebs cycle in bone

Submitted on May 22, 1964