IMPORTANCE OF VENULAR FLOW IN CONTROL OF ARTERIOLAR DIAMETER IN HAMSTER CREMASTER MUSCLE

These experiments tested the hypothesis that an intact venular flow is important for the control of upstream arteriolar diameter during an i ncrease in metabolism. A silicone stopcock grease dam was placed acros s the distal portion of the cremaster muscle to localize treatment of the metabolic stimulator 2,4-dinitrophenol (DNP). Thus only the distal area would have an increased metabolic rate, with the proximal area o f the cremaster having a normal metabolic rate. During DNP treatment, the first-order venule, approximately 5 mm proximal to the Silastic da m, was occluded to prevent the transport of metabolites. DNP treatment (10 mM) resulted in a significant increase in the arteriolar diameter from 75 +/- 3 to 90 +/- 4 mum (n = 7, P < 0.05), 12.1 +/- 0.3 mm upst ream from the distal region. After venular occlusion, arteriolar diame ter decreased to 78 +/- 3 mum (P < 0.05). As an additional test of our hypothesis we altered the experimental sequence. DNP treatment during venular occlusion did not affect arteriolar diameter, but after relea se of the occlusion there was a significant increase in arteriolar dia meter from 78 +/- 3 to 91 +/- 4 mum (P < 0.05). These results suggest that an intact venular flow is necessary for control of arteriolar dia meter during an increased metabolic rate caused by DNP treatment, prov iding evidence for the significance of the venular-arteriolar diffusio n of vaso-active metabolites.