Measurement of Krogh's diffusion constant of CO2 in respiring muscle at various CO2 levels: Evidence for facilitated diffusion

Publisher Website
Google Scholar
Abstract
Krogh's diffusion constant for CO2, KCO2, was determined in respiring muscle tissue at various levels of tissueP CO2, between 10 and 160 torr, using a technique described previously (Kawashiro et al., 1975). With increasing mean tissueP CO2, KCO2 declined towards an apparently asymptotic value. The relationship between KCO2 (10−9 mmol·cm−1·min−1·torr−1) andP CO2 (torr) at 37° C could be approximated by the equation KCO2=17.3 {1+1.72·exp(-0.027{P CO2)}AtP CO2=0 toor KCO2 exceeded the asymptotic value, which was virtually attained atP CO2=100 torr, by more than a factor of two. Thus CO2 diffusion in muscle appears to be facilitated in the lowP CO2 range. Specific CO2 production rate of tissue, which was determined simultaneously, did not vary with CO2 in theP CO2 range studied. Effects of facilitated CO2 transport on CO2 exchange in muscle are assessed using simple models. In the presence of CO2 facilitation muscleP CO2 is reduced, particularly during exercise.