Oxygen diffusion coefficient in isolated chicken red and white skeletal muscle fibers in ontogenesis

Oxygen diffusion from medium to cultured isolated muscle fibers from red ga strocnemius muscle (deep part) (RGM) and white pectoralis muscle (WPM) of e mbryonic and postnatal chickens (about 6 months) was explored. The intracel lular effective O-2 diffusion coefficient (D-i) in muscle fiber was calcula ted from a model of a cylindrical fiber with a uniform distribution of an o xygen sink based on these experimentally measured parameters: critical tens ion of O-2 (PO2) on the surface of a fiber, specific rate of O-2 consumptio n by a weight unit of muscle fibers ((V) over dot O-2), and average diamete r of muscle fibers. The results document the rapid hypertrophic growth of R GM fibers when compared to WPM fibers in the second half of the embryonic p eriod and the higher values of (V) over dot O-2 and critical PO2 during the ontogenetic period under study. The oxygen D-i in RGM fibers of embryos an d 1-day chickens was two to three times higher than observed for WPM fibers . For senior chickens, the oxygen D-i value in RGM and WPM fibers does not differ. The D-i of O-2 in both RGM and WPM fibers increased from 1.4-2.7 x 10(-8) to 90-95 x 10(-8) cm(2)/s with an ontogenetic increase in fiber diam eter from 7.5 to 67.0 mu m. At all stages the oxygen D-i values in RGM and WPM fibers are significantly lower than the O-2 diffusion coefficient in wa ter: for 11-day embryos they are 889 and 1714 times lower and for adult ind ividuals 25 and 27 times lower, respectively. Why oxygen D-i values in RGM and WPM fibers are so low and why they are gradually increasing during the course of hypertrophic ontogenetic growth are still unclear. (C) 2000 Acade mic Press.