Renal afferent and efferent arterioles of the rabbit.

The present study employed our microdissection-digestion technique to determine the three dimensional organization of the walls of the afferent and efferent arterioles of the adult rabbit kidney. Each smooth muscle cell of an afferent arteriole is characterized by a somal enlargement and two lateral processes. The cells of the distal segment of the afferent arterioles are modified into myoepithelioid cells, which are closely apposed to one another. The cells of the proximal efferent arteriole are irregularly shaped and regions of adjacent cells may be separated from one another so that gaps exist and areas of the underlying endothelium are not covered by smooth muscle cells. The cells of the distal segments of efferent arterioles are multipolar pericytes, of which the processes branch. Thus the afferent arteriole possesses a complete muscular wall while only the proximal efferent possesses smooth muscle cells with a sphincteric orientation. The distal efferent arteriole possesses pericytes that appear to have a limited capability to modulate renal hemodynamics.