title: Conditions for dipyridamole potentiation of skeletal muscle active hyperemia.
abstract: The effects of dipyridamole on active hyperemia were evaluated in dog gracilis muscles undergoing sustained isometric contractions. Muscles were stimulated to contract for 5, 15, 25, and 50 s at 20% maximal tension (20% Tmax) or for 10 s at 100% Tmax during intra-arterial infusion of either saline or dipyridamole (1 microM). In two separate groups of dogs, muscles were stimulated to contract under free-flow or restricted-flow (ischemic) conditions. In the later group, blood flow was reduced to 50% of precontraction level during the period of contraction. Dipyridamole increased resting vascular conductance by about 45%; however, it did not affect the change in vascular conductance resulting from muscle contraction. The recovery time for active hyperemia following free-flow contractions at 20% Tmax was not altered by dipyridamole. However, dipyridamole increased the recovery time following 50 s of restricted-flow contraction (20% Tmax) and 10 s of 100% Tmax contractions by 46 and 169%, respectively. These results suggest that adenosine contributes to active hyperemia following sustained ischemic contractions at 20% Tmax and contractions at 100% Tmax but not from contractions at 20% Tmax where blood flow is allowed to increase freely.
mesh_terms: D000818:Animals; D001808:Blood Vessels / Q000503:physiopathology; D004176:Dipyridamole / Q000494:pharmacology*; D004285:Dogs; D005260:Female; D006940:Hyperemia / Q000503:physiopathology*; D007537:Isometric Contraction; D008297:Male; D009132:Muscles / Q000098:blood supply*; D012039:Regional Blood Flow / Q000187:drug effects
chemical_list: D004176:Dipyridamole