Abstract

The venous compartment plays a critical role in circulatory control. The present series of experiments was conducted to assess simultaneously effects of vasoactive drugs on arterial resistance and venous capacitance vessels of the rat hindquarters perfused with physiological salt solutions (SS). Retrograde infusion of SS into rat hindquarters via the vena cava resulted in an increase in hindquarters venous pressure (Pv). The range of mean volumes required to increase Pv to 20 and 30 mm Hg was 1.7 +/- 0.1 to 2.9 +/- 0.4 and 3.8 +/- 0.3 to 6.9 +/- 0.3 ml, respectively, in various groups of rats during a control period. Perfusion of the hindquarters with an SS containing 80 mM K+ reduced the volume required to increase Pv to 20 and 30 mm Hg to 47 +/- 2 and 42 +/- 2% of control, respectively, indicating venoconstriction. K+ (80 mM) SS also increased aterial perfusion pressure (Pa; measured from a sidearm off of the inflow catheter) to 141 +/- 9 mm Hg, indicating arterial vasoconstriction. Arterial and venous responses to 80 mM K+ were attenuated markedly by perfusion with SS containing zero Ca and 2 mM ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid, indicating dependence on extracellular Ca. Phentolamine (10(-5) M) attenuated the arterial and venous response to 80 mM K+, indicating an alpha adrenergic contribution. Arterial responses to 80 mM K+ were attenuated markedly by the Ca entry blockers nifedipine (10(-6) and 10(-5) M) and verapamil (10(-6) and 10(-5) M). In contrast, venous responses were not affected by nifedipine and were reduced slightly only at the high concentration of verapamil.(ABSTRACT TRUNCATED AT 250 WORDS)