AJP - Gastrointestinal and Liver Physiology, Vol 247, Issue 3 279-G283, Copyright © 1984 by American Physiological Society
Sympathetic stimulation and intestinal capillary fluid exchange
D. N. Granger, J. A. Barrowman, S. L. Harper, P. R. Kvietys and R. J. Korthuis
Sympathetic nerve stimulation is generally considered not to alter
intestinal capillary pressure or filtration rate because of appropriate
adjustments in the pre-to-postcapillary resistance ratio. To directly
assess this possibility, we measured lymph flow, capillary pressure,
capillary filtration coefficient, and the transcapillary oncotic pressure
gradient in the cat small intestine. Measurements were taken under control
conditions and during the steady-state phase of periarterial nerve
stimulation, i.e., following completion of the escape phase. Venous outflow
pressure was held constant (0 mmHg) during the entire experiment. Nerve
stimulation resulted in a significant reduction of lymph flow (by 65%),
capillary filtration coefficient (by 75%), and capillary pressure (by 15%).
Interstitial fluid pressure, calculated from the measured parameters in the
Starling equation, was also reduced (from -0.74 to -2.53 mmHg) by nerve
stimulation. The results of this study indicate that intestinal capillary
pressure and capillary filtration rate are not "autoregulated" during
sympathetic nerve stimulation. Capillary derecruitment appears to be
largely responsible for the dramatic reduction in filtration rate
associated with adrenergic stimulation.
