Tone, autoregulatory properties, and wall thickness-to-radius ratio in skeletal muscle arterioles.

Internal diameter, wall thickness, wall thickness-to-radius ratio (W/r), and blood flow velocity in arterioles of different branching orders were measured in the rat cremaster muscle. The heterogeneity of W/r increased in more distal orders. During papaverine treatment, there was a direct correlation between vasodilation and W/r. When pressure was decreased by 20%, 42% of arterioles showed autoregulation; the remaining arterioles constricted in proportion to initial W/r. Similarly, the dilatation of arterioles with autoregulatory properties increased with initial W/r. It is concluded that W/r is an important parameter quantitatively related to tone, mechanical characteristics, and autoregulatory properties of arterioles.