Exaggerated Pressor Response to Intermittent Contraction in Type 1 Diabetic Rats

Abstract

Type 1 diabetes mellitus (T1DM) is associated with an impaired regulation of autonomic and cardiovascular responses during exercise, an effect attributable, in part, to the exercise pressor reflex. Previously, we have found that the pressor responses to both static muscle contraction and to tendon stretch are exaggerated in the early stage of T1DM. However, it is not known whether a similar response is present during dynamic exercise. Moreover, other studies have suggested that endothelial dysfunction manifests early in T1DM, which may impair muscle perfusion during exercise leading to an increased stimulation of the exercise pressor reflex. Therefore, the purpose of this study was to test whether T1DM rats have an exaggerated pressor and an attenuated blood flow response to intermittent contraction. To do this, we measured the exercise pressor reflex in unanesthetized, decerebrated T1DM (Streptozotocin 50mg/kg i.p; STZ: body weight: 328 ± 39g) and healthy (CTL: body weight: 264 ± 17g, n=5) Sprague Dawley rats by intermittently contracting the hindlimb for 30 s while continuously measuring mean arterial pressure (MAP), heart rate (HR) and popliteal arterial blood flow (BF). Popliteal vascular conductance was estimated by dividing popliteal BF by MAP. BF and VC are reported as mean change from baseline.Muscle contraction significantly increased peak MAP (STZ: 32 ± 4 mmHg, n=3; CTL: 17 ± 4 mmHg, n=5, p<0.05) but not HR (STZ: 20 ± 4 mmHg, n=3; CTL: 14 ± 6 mmHg, n=5, p>0.05) to similar developed tensions (p>0.05) in T1DM rats compared to CTL rats. Muscle contraction increased hindlimb BF (STZ: 858 ± 379 μl/min, n=3; CTL: 220 ± 40 μl/min, n=2) and hindlimb vascular conductance (STZ: 7.4 ± 4.1 μl/min/mmHg, n=3; CTL: 2.2 ± 0.3 μl/min/mmHg, n=2) from baseline in STZ and CTL rats, however, this was not significantly different between groups (p>0.05). These findings are consistent with our previous studies that found that early stage T1DM rats had an exaggerated pressor response to static muscle contraction. Furthermore, the finding that blood flow delivery was not impaired in the T1DM rats may suggest that a mismatch between metabolic demand and oxygen delivery is not contributing to the exaggerated response.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.