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Abstract:
Glomeruli from adult normal male Wistar rats were obtained by teasing a cortex slice with stainless steel needles. The enzyme content and the morphologic aspect of these glomeruli were assessed as a preliminary step to further metabolic studies. Robinson's medium appeared to be the most suitable medium. There was no loss of glutamic dehydrogenase, glucose-6-phosphate dehydrogenase or acid phosphatase. Lactate dehydrogenase was lost to about 50%. Electron microscopy showed morphologic signs of damage in the podocytes. The glomerular oxygen uptake was measured with the help of the Cartesian diver technique, using approximately 20 glomeruli per assay. The endogenous respiratory rate was linear for at least three hours. The endogenous respiratory rate was linear for at least three hours. The mean dry wt of lyophilized glomeruli was determined for 13 rats for which the glomerular oxygen uptake had been measured, and these data showed a glomerular Q-02 of 4 mul/hr/mg of dry wt. The following substances were tested for their influence on the oxygen uptake: acetate, alpha-oxoglutarate, citrate, oxalacetate, glutamate, alanine, all 10 mM; succinate, 2.5, 5 and 10 mM; glucose, 5, 10 and 20 mM; fructose 10 and 20 mM; and palmitate. Citrate increases the O-2 uptake/hr/glomerulus by 30%; glucose, 20 mM, by 30%; and succinate, 2.5 mM by 50% and 10 mM by 190%. In a Robinson's medium containing 35 mg of albumin/ml, the endogenous respiration is not different from that obtained in the inorganic medium but the oxygen uptake is increased 26% by glucose, 10 mM. From these data, it can be concluded that the oxygen uptake of the glomerulus is small. This fact explains its resistance to anoxia. The systematic investigation of possible substrates indicate that glucose, citrate and succinate may play a role in supporting this small oxidative metabolism.