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Impact of early mammalian development on the response of the O 2 transport system to muscle contraction
Author(s) -
Dodhy Sami C,
Pittman Roland
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.831.6
Subject(s) - skeletal muscle , microcirculation , contraction (grammar) , oxygen transport , chemistry , medicine , biophysics , anatomy , oxygen , biology , organic chemistry
A continuous supply of O 2 to the cells in the body is necessary to maintain normal physiological function and the microcirculation is especially important in this matter as it is the site of O 2 exchange. Under conditions of active/functional hyperemia following muscle contractions, the O 2 transport system in older subjects does not appear to respond as rapidly and to the same degree as in younger subjects. With aging, elements of the O 2 transport and regulatory systems are changed in such a way that matching O 2 supply to O 2 demand does not work as well in older as in younger subjects. An intravital microscopic approach is being used to show that developmental changes in the O 2 transport system begin earlier than previously thought. Significant and rapid changes in the microvascular network of skeletal muscle have been observed during the first few weeks of postnatal development. Four different developmental groups of male Sprague‐Dawley rats (8, 16, 24, and 52 weeks) are used to investigate changes in the O 2 demand component of the transport system by measuring oxygen consumption (VO 2 ) and the P ISF O 2 dependence of VO 2 under conditions of rest and contraction. VO 2 was measured with a quasi‐continuous, flash‐synchronized, rapidly pressurizing airbag system to briefly arrest flow and determine the rate of change in oxygen tension (dPO 2 /dt). Changes in the O 2 supply component are investigated by measuring capillary and interstitial fluid PO 2 (P cap O 2 and P ISF O 2 respectively, using phosphorescence quenching microscopy) and surface area available for O 2 exchange (i.e., capillary density). Preliminary experiments were carried out on six animals that ranged from 8 w to 20 w in age with an average weight of 331 ± 35 g. Average baseline VO 2 for the 8 w group was 307 ± 26 nL O 2 /cm 3 ·s (n = 6), average baseline VO 2 for the 16 w group was 287 ± 31 nL O 2 /cm 3 ·s (n = 6), and average baseline VO 2 for those in the 24 w group was 264 ± 12 nL O 2 /cm 3 ·s (n = 6). Average baseline P ISF O 2 for the 8 w group was 68 ± 3 mmHg (n = 6), average baseline P ISF O 2 for the 16 w group was 74 ± 4 mmHg (n = 6), and average baseline P ISF O 2 for the 24 w group was 68 ± 3 mmHg (n = 6). The observed decreases in tissue VO 2 are consistent with literature showing that whole body VO 2 decreases from 499, 396, to 345 nL O 2 /cm 3 ·s at 8 w, 16 w, and 24 w, respectively. However, it is still unclear how well matched O 2 supply and demand are. As O 2 demand increases by increasing muscle contraction, O 2 supply should also increase to match it and P ISF O 2 is at least one element that links the two components of the transport system which requires further investigation.