Ageing impairs endothelium-dependent vasodilatation and alters redox signalling in diaphragm arterioles from male and female Fischer-344 rats.

Abstract

Diaphragm hyperaemia and regional blood flow distribution are impaired with ageing, potentially consequent to altered vascular structure and/or diminished vasomotor function. Evidence from locomotory skeletal muscle suggests that age-related diaphragm vasomotor dysfunction may be related to a blunted endothelium-mediated vasodilatation, decreased nitric oxide (NO) bioavailability and/or augmented reactive oxygen species (ROS) generation. We hypothesized that, in the medial costal diaphragm with old age, there would be fewer feed arteries (FAs) and impaired vasomotor function, via endothelium-specific mechanisms, in first-order (1A) arterioles. In young (Y) and old (O) Fischer-344 rats, the number of medial costal diaphragm FAs was quantified. 1A arterioles (117-220 µm) were isolated, cannulated and pressurized via hydrostatic reservoirs. Thereafter endothelium-dependent (via ACh) vasodilatory responses were assessed. In a separate set of arterioles, ACh-mediated dilatation was assessed before and after treatment with the superoxide dismutase mimetic Tempol (100 µm) and Tempol plus the hydrogen peroxide (H