The effect of hypoperfusion on the capillary distribution of leukocytes in cross-striated muscle

In order to analyse whether microvascular redistribution of the leukocytes has any influence on the development of leukocyte capillary plugging at low flow states, the arteriole to capillary distribution of leukocytes was studied with vital microscopy in the rat cremaster muscle at normal perfusion pressure and after blood pressure reduction by 50% through aortic clamping. The reduction of the blood pressure led to a redistribution of the leukocytes, characterized by a shift of the leukocyte flux from capillaries at the downstream end of the arterioles towards more proximal branches in 8 of 19 networks studied, but flow cessation due to permanent leukocyte plugging was observed in only 2 of 94 capillaries observed. The arterioles of the 8 networks showing redistribution of the leukocytes had a significantly larger diameter than the rest of the arterioles. A possible explanation to the redistribution of leukocytes in 8 of the networks might be that their wider arterioles allowed a peripheral displacement and a skimming off of the leukocytes upon pressure reduction. The results from this investigation do not indicate that redistribution of leukocytes in the capillary networks of muscle should be significantly involved in the development of permanent leukocyte capillary plugging at low flow states.