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Blood and isoproterenol reduce capillary permeability in cat hindlimb
Insights
In cat hindlimbs, blood reduced capillary filtration coefficient (CFC) without papaverine, primarily due to its cell fraction. Isoproterenol showed a minor CFC-reducing effect in blood-free conditions.
Area of Science:
- Physiology
- Cardiovascular Research
- Microcirculation
Background:
- Previous studies indicated plasma counteracts permeability increases caused by blood-free perfusion with papaverine.
- The role of plasma in modulating capillary permeability without papaverine remained unclear.
- Understanding factors affecting capillary filtration coefficient (CFC) is crucial for cardiovascular health.
Purpose of the Study:
- To investigate the effect of plasma on capillary filtration coefficient (CFC) in cat hindlimbs in the absence of papaverine.
- To compare the CFC-reducing effects of blood, plasma, and isoproterenol in a blood-free albumin perfusate.
- To elucidate the components of blood responsible for modulating capillary permeability.
Main Methods:
- Cat hindlimbs were perfused with blood-free albumin-electrolyte solution.
- Capillary filtration coefficient (CFC) was measured under various perfusate conditions: blood-free albumin, albumin with blood, albumin with isoproterenol, and albumin with both blood and isoproterenol.
- Comparative analysis of CFC values across different experimental groups.
Main Results:
- Blood-free albumin perfusion resulted in a CFC of 0.017 +/- 0.006 ml x min-1 x mmHg-1 x 100 g muscle-1.
- Presence of blood reduced CFC to 0.012 +/- 0.002, while isoproterenol showed a smaller reduction (0.014 +/- 0.003).
- Blood significantly reduced CFC (P < 0.005) when added to a blood-free albumin perfusate containing isoproterenol, suggesting the cell fraction is key.
Conclusions:
- In the absence of papaverine, the primary CFC-reducing effect of blood is attributed to its cellular components.
- Isoproterenol exhibits a minor CFC-reducing effect under blood-free conditions.
- The observed plasma effect differs from earlier findings when papaverine was present.
Abstract:
In an earlier study, plasma was observed to counteract the permeability-increasing effects of blood-free perfusion when papaverine was present in the perfusate. To determine if this plasma effect was still present in the absence of papaverine, cat hindlimbs were perfused with a blood-free albumin-electrolyte solution, and capillary filtration coefficient (CFC) was measured. These data were compared with CFC values obtained when blood, plasma, or isoproterenol were present in the albumin perfusate. In separate groups of animals, CFC was observed to be 0.017 +/- 0.006 (SD, n = 26) ml X min-1 X mmHg-1 X 100 g muscle-1 during blood-free albumin perfusion, 0.012 +/- 0.002 (n = 24) when blood was present, 0.014 +/- 0.003 when isoproterenol was present, and 0.010 +/- 0.002 (n = 33) when both blood and isoproterenol were present. In a separate study, it was observed that 1) isoproterenol could reduce CFC by 11% when added to blood-free perfusate, 2) plasma had a similar but smaller and more variable effect than isoproterenol, 3) plasma had no consistent effect on CFC when added to a blood-free albumin perfusate containing isoproterenol, and 4) blood could reduce CFC significantly (P less than 0.005), from 0.014 +/- 0.003 to 0.0094 +/- 0.002 (n = 7), when added to a blood-free albumin perfusate containing isoproterenol. It was concluded that, in the absence of papaverine, the principal CFC-reducing effect of blood lay in the cell fraction and that isoproterenol had a small CFC-reducing effect under blood-free conditions. This result contrasts with the plasma effect reported earlier.