Impact of Increased Intramuscular Perfusion Heterogeneity on Skeletal Muscle Microvascular Hematocrit in the Metabolic Syndrome

ObjectiveTo determine H-MV and PS in skeletal muscle of OZR and evaluate the impact of increased microvascular perfusion heterogeneity on mass transport/exchange. MethodsThe in situ gastrocnemius muscle from OZR and LZR was examined under control conditions and following pretreatment with TEMPOL (antioxidant)/SQ-29548 (PGH(2)/TxA(2) receptor antagonist), phentolamine (adrenergic antagonist), or all agents combined. A spike input of a labeled blood tracer cocktail was injected into the perfusing artery. Tracer washout was analyzed using models for H-MV and PS. H-T was determined in in situ cremaster muscle of OZR and LZR using videomicroscopy. ResultsH(MV) was decreased in OZR versus LZR. While TEMPOL/SQ-29548 or phentolamine had minor effects, treatment with all three agents improved H-MV in OZR. H-T was not different between strains, although variability was increased in OZR, and normalized following treatment with all three agents. PS was reduced in OZR and was not impacted by intervention. ConclusionsIncreased microvascular perfusion heterogeneity in OZR reduces H-MV in muscle vascular networks and increases its variability, potentially contributing to premature muscle fatigue. While targeted interventions can ameliorate this, the reduced microvascular surface area is not acutely reversible.