عنوان

Oxygen delivery by capillary networks in striated muscle

TLpq304218998

انگلیسی

Oxygen delivery by capillary networks in striated muscle

[Thesis]

B. R. Berg

I. H. Sarelius

University of Rochester

1995

518

Ph.D.

University of Rochester

1995

Architecture and flow variables affecting oxygen delivery were measured in cremaster muscle capillary networks of anesthetized (pentobarbital sodium, 70 mg/kg, i.p.) Syrian hamsters (HSD:SYR). Networks consist of capillary sub-groups, modules. In juvenile (51 days) and adult (79 days) animals, modules exhibited a preferred size (usd\rm 14.5\pm1.1(S.E.)\ versus\ 12.6\pm1.6\ segments,\ 1.87\pm0.16\times10\sp5\ versus\ 1.81\pm0.3\times10\sp5\ m\sp2usd perfused tissue area, and usd\rm 3.07\pm0.23\times10\sp3\ versus\ 3.02\pm0.45\times10\sp3\ \muusdm total segment length in juveniles versus adults). Module blood flow was proportional to expected metabolism and the number of modules directly determined network size and cell inflow. Local stimulation of muscle fibers associated with individual modules increased capillary erythrocyte flux and content in proportion to the contraction frequency; the relative increase over rest was usd\rm 248.8\pm21.5\%,\ 310.5\pm25.9\%,\ 318.6\pm24.1\%\ for\ flux\ and\ 145.8\pm15.7\%,\ 170.1\pm12.3\%,\ 221.5\pm35.1\%usd for content at 2, 4, and 8 Hz. The module inflow arteriole dilated with contraction of muscle fibers which were >500 mum from the inflow vessel and associated only with the module capillaries; the relative increase over rest was usd\rm 114.7\pm5.5\%,\ 140.6\pm14.6\%,\ 159.8\pm15.5\%usd at 2, 4, and 8 Hz. Mean capillary wall PO2 (usd\rm\overline{PO}\sb{2\sb{cw}}usd) was modelled using in vivo data. Resting network usd\rm\overline{PO}\sb{2\sb{cw}}usd remained uniform during maturation (25.2 0.4 versus 22.9 0.8 mmHg at 51 and 79 days) implying that network usd\rm\overline{PO}\sb{2\sb{cw}}usd is actively regulated. In functional hyperemia, recruited networks had higher usd\rm\overline{PO}\sb{2\sb{cw}}usd than continuously perfused networks in adult animals (18.8 1.4 versus 12.2 0.7 mmHg). At normal hematocrit, the cell flux into, but, importantly, not flow distribution within, the module determined usd\rm\overline{PO}\sb{2\sb{cw}}usd. At hematocrit <25% normal, erythrocyte concentration significantly influenced usd\rm\overline{PO}\sb{2\sb{cw}}usd. In summary, networks are comprised of modules. Module architecture maintains a preferred size, while module blood flow is proportional to metabolism. In functional hyperemia, signals arising at the capillary level control module inflow proportionately to metabolism. However, the flow distribution within a module does not affect usd\rm\overline{PO}\sb{2\sb{cw}}usd. Overall, these data show that coupling of oxygen delivery and oxidative metabolism occurs at the level of individual capillary modules, which implies that modules are the smallest regulated unit of oxygen delivery in striated muscle.

Anatomy & physiology

Animals

Animals

Biological sciences

Biophysics

Biophysics

B. R. Berg

I. H. Sarelius

p

[Thesis]

276903

a

Y