The relationship between contraction-induced arteriolar vasodilation, estimated blood flow (BF), and tissue oxygen tension (PtO<inf>2</inf>) in skeletal muscle of young rats was investigated. Arteriolar diameters, BF, and PtO<inf>2</inf> were measured during cremaster muscle stimulation at 2, 4, and 8 Hz. At a suffusate PO<inf>2</inf> (PsO<inf>2</inf>) of 5–10 mm Hg, the caliber of second-order arterioles (2A, > 30 µm diameter) did not significantly increase after 8 Hz stimulation. In contrast, with the same PsO<inf>2</inf>, third-order arterioles (3A, < 30 µm diameter) significantly dilated to 127 ± 9 (SE), 135 ± 12, and 160 ± 13% of control, respectively at 2, 4, and 8 Hz stimulation. Third-order arteriolar BFs at the end of the stimulation periods were: 119 ± 18, 176 ± 14, and 258 ± 43% of control, respectively. PtO<inf>2</inf> remained essentially constant during and following 4 and 8 Hz stimulation if the systemic arterial blood pressure exceeded 80 mm Hg. When PsO<inf>2</inf> was increased to 65–70 mm Hg, neither 3A diameters nor PtO<inf>2</inf> during 8 Hz stimulation differed from paired comparisons of the response at low PsO<inf>2</inf>. These data indicate that dilation of small arterioles during increased muscle metabolic activity can occur without a mandatory change in PtO<inf>2</inf>. This circumstance is unaffected by a substantially increased supply of oxygen to the tissue.
- Cremaster muscle
- Functional hyperemia
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine