Capillary permeability and sympathetic activity in canine subcutaneous adipose tissue

Abstract

PREVIOUS studies on the exchange properties of the microvasculature of canine subcutaneous adipose tissue have shown that electrical stimulation of the sympathetic nerves with frequencies within the physiological range, induced vasoconstriction accompanied by an increase in the transcapillary hydrodynamic conductivity expressed by the capillary filtration coefficient (CFC) (ref. 1). Given that CFC is a function of the product of the surface area available for exchange and the permeability of the capillary wall^2,3 these two factors must be separated to establish the functional properties of this vascular reaction. In attempting to do this, the clearance of locally injected Na¹²⁵I was measured at constant flow perfusion, and was found to be significantly reduced during sympathetic stimulation. Similarly the permeability-surface area product (PS) of the vascular bed measured by the extraction of ⁸⁶Rb in subcutaneous adipose tissue decreased as a function of sympathetic stimulation (ref. 4 and J. Gainer, B. Linde, and S.R., unpublished).