The Endogenous Respiratory Quotient of Bovine Dental Pulp

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Abstract
Pulps from bovine molars that were dentinogenically very active ("embryonic"), moderately active ("young"), and relatively quiescent ("mature") provided the tissue slices that were observed by the Warburg method. The method was simplified by the use of Stanley-Tracewell reaction vessels and pardee''s "CO2 buffer". Oxygen consumption and carbon dioxide production were measured alternately on the same samples for 30 minute periods through 9 complete cycles. For the 1st 3 hours the R.Q. of "mature" pulp remained at 1.0 or higher but then gradually declined to the level of about 0.7 by the end of 5 hours. The R.Q. of "young" pulp was 1st observed to be 0.94 but dropped to around 0.7 by the end of 4 hours. "Embryonic" pulp had an R.Q. of 0.86 at the end of the 1st hour that dropped to 0.74 by the end of about 3 hours. The pulp has only a small tissue supply of available glucose which is used at a rate commensurate with that of the level of metabolic activity of the tissue. When this is exhausted, further respiratory activity is probably sustained by protein and lipid constituents of the tissue. A supplementary study designed to measure only respiratory carbon dioxide showed that when glucose was the substrate, the R.Q. was 0.93. This suggested that the previously observed R.Q. values higher than 1.0 were probably the result of a previously unreported significant glycolytic capacity of the pulp.