AJP - Heart and Circulatory Physiology, Vol 249, Issue 4 792-H798, Copyright © 1985 by American Physiological Society
Effect of temperature on transcapillary water movement in isolated cat hindlimb
M. B. Wolf and P. D. Watson
Capillary filtration coefficient (CFC) was measured in the isolated cat
hindlimb preparation, perfused at 20 ml X min-1 X 100 g muscle-1 with a
perfusate containing 6 g/dl albumin and normal electrolyte concentrations,
to which were added 50 ml of the cat's blood and 6 micrograms of the
vasodilator isoproterenol. CFC was determined three to six times in an
initial control period during which the tissue temperature (measured by a
5-mm disk thermistor implanted in a thigh muscle) was controlled near 37
degrees C. Tissue temperature was decreased to 5-10 degrees C by lowering
perfusate and ambient air temperatures. About 50 min were required for
tissue temperature equilibration. CFC was measured at low temperature and
then again at 37 degrees C. For nine experiments, the ratio of CFC at low
temperature to that in the 37 degrees C control periods averaged 87% of the
ratio of water viscosity at 37 degrees C to that at low temperature. The
activation energy for water calculated from these data was 5.0 kcal/mol.
These results may be explained by all transcapillary water flow moving by
diffusion through narrow pores or by about 90% moving by convection, with
the remainder going through a lipid pathway. However, the results may be
entirely due to a direct effect of temperature on the geometry of the
transcapillary pathway for water movement.
