Open AccessRegulation of capillary hemodynamics by K ATP channels in resting skeletal muscle
Author(s) -
Hirai Daniel M.,
Tabuchi Ayaka,
Craig Jesse C.,
Colburn Trenton D.,
Musch Timothy I.,
Poole David C.
Publication year - 2021
Publication title -
physiological reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 39
ISSN - 2051-817X
DOI - 10.14814/phy2.14803
Subject(s) - skeletal muscle , medicine , hemodynamics , microcirculation , hematocrit , endocrinology , chemistry , red blood cell , intravital microscopy , blood flow , myocyte , anatomy , biology
ATP‐sensitive K + channels (K ATP ) have been implicated in the regulation of resting vascular smooth muscle membrane potential and tone. However, whether K ATP channels modulate skeletal muscle microvascular hemodynamics at the capillary level (the primary site for blood‐myocyte O 2 exchange) remains unknown. We tested the hypothesis that K ATP channel inhibition would reduce the proportion of capillaries supporting continuous red blood cell (RBC) flow and impair RBC hemodynamics and distribution in perfused capillaries within resting skeletal muscle. RBC flux ( f RBC ), velocity ( V RBC ), and capillary tube hematocrit (Hct cap ) were assessed via intravital microscopy of the rat spinotrapezius muscle ( n = 6) under control (CON) and glibenclamide (GLI; K ATP channel antagonist; 10 µM) superfusion conditions. There were no differences in mean arterial pressure (CON:120 ± 5, GLI:124 ± 5 mmHg; p > 0.05) or heart rate (CON:322 ± 32, GLI:337 ± 33 beats/min; p > 0.05) between conditions. The %RBC‐flowing capillaries were not altered between conditions (CON:87 ± 2, GLI:85 ± 1%; p > 0.05). In RBC‐perfused capillaries, GLI reduced f RBC (CON:20.1 ± 1.8, GLI:14.6 ± 1.3 cells/s; p < 0.05) and V RBC (CON:240 ± 17, GLI:182 ± 17 µm/s; p < 0.05) but not Hct cap (CON:0.26 ± 0.01, GLI:0.26 ± 0.01; p > 0.05). The absence of GLI effects on the %RBC‐flowing capillaries and Hct cap indicates preserved muscle O 2 diffusing capacity (DO 2 m). In contrast, GLI lowered both f RBC and V RBC thus impairing perfusive microvascular O 2 transport (Q̇m) and lengthening RBC capillary transit times, respectively. Given the interdependence between diffusive and perfusive O 2 conductances (i.e., %O 2 extraction∝DO 2 m/Q̇m), such GLI alterations are expected to elevate muscle %O 2 extraction to sustain a given metabolic rate. These results support that K ATP channels regulate capillary hemodynamics and, therefore, microvascular gas exchange in resting skeletal muscle.