Heterogeneity of the afferent arteriole—correlations between morphology and function

Abstract

The afferent arteriole (AA) is an important structural and regulatory site of blood pressure maintenance and renal salt and water conservation. The AA is considered a typical resistance vessel with ring-like smooth muscle cells in its wall, covered by a homogenous endothelial layer. It also contains renin granular cells mainly at its distal, juxtaglomerular end [1]. These cells become myosin-negative, round-shaped cells producing a large number of renin granules in their cytoplasm [2]. The AA is part of a functional syncytium at the vascular pole of renal corpuscle, called the juxtaglomerular apparatus (JGA), which consists of the afferent and efferent arterioles, the macula densa (MD) cells of the thick ascending limb and the extraglomerular mesangium [1]. Two major regulatory processes have been traditionally attributed to the AA-JGA: the control of vascular resistance and renin release. Both direct mechanisms (myogenic, neurohumoral) and indirect mechanisms (tubuloglomerular and AA short-loop feedback) are involved in the regulation of AA vascular resistance [3]. Also, it is accepted that the major portion of plasma renin originates from the renin granular cells of the JGA [4]. The AA has been widely and extensively studied and several comprehensive reviews are available [5–8]. The present short review focuses on some selected morphological and functional features of the distal portion of AA. Historical background