The microvasculature in skeletal muscle. II. Arteriolar network anatomy in normotensive and spontaneously hypertensive rats.

A quantitative comparison of the anatomical arrangement of arterioles in the skeletal muscle of mature (16 to 20-week-old) Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) is provided. In both species several feeding arterioles supply blood to a network of arterioles covering the entire muscle, designated as arcade arterioles. The connections from the arcade arterioles to the capillary network are provided by the transverse arterioles. Comparison of the spinotrapezius muscle of the WKY and the SHR shows several types of rearrangement of the network. In both species there is a wide distribution of vessel size in the arcade and transverse arterioles. The length of the arcade arterioles per unit muscle volume is higher in the SHR, forming a denser network. There are almost twice as many transverse arteriolar trees per unit tissue volume in hypertensive animals although on the average each transverse tree has shorter branches. No evidence for significant anatomical rarefaction was found among arcade and transverse arterioles. Arcade arterioles following maximal dilation were found to be 25% narrower in the SHR, whereas for transverse arterioles no differences in diameter could be detected under these vasodilated conditions.