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Microvascular adaptations during maturation of striated muscle
Insights
Muscle microcirculation changes significantly with age. Juvenile hamsters have higher capillary density, but adult muscles show greater functional reserve for oxygen supply.
Area of Science:
- Physiology
- Microcirculation Research
- Developmental Biology
Background:
- Capillary density is crucial for tissue oxygen supply, alongside erythrocyte flow and hematocrit.
- Striated muscle microcirculation undergoes significant changes during maturation.
Purpose of the Study:
- To investigate microcirculatory changes in hamster cremaster muscle during development.
- To quantify alterations in capillary density, erythrocyte flow, and hematocrit with age.
Main Methods:
- Studied microcirculation in hamster cremaster muscle at various developmental stages.
- Measured capillary density, intercapillary distance, capillary length, and vessel tortuosity.
- Quantified erythrocyte flow per capillary and capillary hematocrit.
Main Results:
- Juvenile microcirculation featured high capillary density, short, tortuous vessels.
- Maturation led to elongated capillaries, decreased capillary density (1626 to 696 capillaries/mm³), reduced erythrocyte flow, and lower hematocrit.
- Adult muscles demonstrated significantly higher functional reserve capacity for all measured parameters compared to juveniles.
Conclusions:
- Age profoundly impacts microvascular parameters essential for tissue oxygenation.
- Developmental changes in microcirculation explain previously conflicting research findings.
Abstract:
It is well known that capillary density in striated muscle changes during maturation. Capillary density is an important determinant of tissue oxygen supply, the other principal determinants being capillary erythrocyte flow and capillary hematocrit. The microcirculation of the hamster cremaster muscle was studied at different stages of development. We found that the microcirculation of juvenile animals was characterized by small intercapillary distances, short capillary lengths, and tortuous vessels. During maturation, the capillaries elongated and developed the more "typical" parallel pattern. Capillary density decreased from 1,626 +/- 60 capillaries . mm-3 at 35 days of age to 696 +/- 65 capillaries . mm-3 at 132 days; erythrocyte flow per capillary decreased from 1,441 +/- 135 to 583 +/- 47 micrometers 3 . s-1; and capillary hematocrit decreased from 21.5 +/- 0.7 to 14.6 +/- 0.6%. Concomitant with these decreases, the functional reserve increased; in adult muscles, capillary density could increase by 42%, erythrocyte flow per capillary by 457.2%, and capillary hematocrit by 112.4%, compared with 7.7, 20.3, and 24.1%, respectively, in immature animals. These observations show that age significantly modifies microvascular parameters related to tissue oxygen supply and provides an explanation for some conflicting observations in the literature.