The structural organization of the kidney of the desert rodent Psammomys obesus

Abstract

The architecture of the desert rodent Psammomys obesus has been studied by means of standard histologic procedures and by single nephron injections. As other rodent kidneys (rat, mouse), the Psammomys kidney consists of two types of nephrons, 66% short looped and 34% long looped nephrons. The cortex is composed of 4 to 5 layers of glomeruli, which lie closely put together, the glomeruli often touch each other. The superficial and the midcortical glomeruli give rise to short looped neophrons, the juxtamedullary to long looped nephrons. In the strongly developed medulla the inner stripe shows the most striking pattern. It consists of two distinct compartments, that of the giant vascular bundles and that of the interbundle regions. The giant vascular bundles consist of about 8 to 14% arterial vasa recta and 39 to 47% venous vasa recta; furthermore they include the thin descending limbs of the short loops of Henle which amount to 44 to 51% of the bundle structures. The tubules of the interbundle regions surround the bundles in a regular pattern. The inner zone is almost completely surrounded by the renal pelvis; the long broad papilla protrudes into the ureter. The thin descending limbs of short looped nephrons traverse the inner stripe inside the giant vascular bundles. Leaving the bundles they turn back within the inner stripe; their ascending limbs lie in the interbundle region. Both limbs of the long loops of Henle run in the interbundle region, together with the ascending limbs of the short loops and the collecting ducts. The long loops penetrate deeply the inner zone. Many bends are found near the tip of the papilla. The renal pelvis has a very specialized form. It penetrates the inner stripe with many complexely shaped extensions, which surround the giant vascular bundles. Large parts of the bundles with their thin walled structures are thus separated from the pelvic urine only by a single layer of cuboidal epithelium. The possible functional importance of the described specializations of the Psammomys kidney (giant vascular bundles, large inner zone, special shape of the renal pelvis) for the urine concentrating and urea recyclng mechanisms is discussed.

Countercurrent exchange in the renal medulla

“…AVR formed within the outer medulla from the capillary plexus of the interbundle region ascend directly to the cortex without rejoining a vascular bundle. The capillary plexus of the interbundle region arises from DVR that peel off from the periphery of the vascular bundles as they pass through the inner stripe (42,43,59,73,91). From this arrangement we infer that countercurrent exchange in the outer medulla occurs between AVR draining the inner medulla and DVR supplying both outer and inner medulla.…”

“…The latter is most prominent in Psammomys and is to be contrasted with the vascular bundle architecture in the outer medulla of other mammalian species (Fig. 2, B-D) (42). Thus vascular bundles that characterize the inner stripe provide for countercurrent exchange between DVR and AVR returning from the inner medulla, and to a variable degree that is species dependent between vasa recta and thin descending limbs of short looped nephrons.…”

“…The "complex" vascular bundle (rat, mouse, Meriones, Psammomys) differs from simple bundles due to the variable incorporation of thin descending limbs of short looped nephrons (6,7,52,59,91). In the rat, the thin descend-ing limb is situated on the periphery of the bundles, whereas in the mouse and Psammomys, short looped thin descending limbs are distributed throughout the vascular bundle (7,42,51,53). In some species, complex vascular bundles coalesce in the outer stripe to form "giant" bundles that traverse the inner stripe ( Fig.…”

Role of renal NO production in the regulation of medullary blood flow

“…The focus of these studies has been on the larger diameter vasa recta vessels of the outer medulla for reasons related to the unique structure and function of the medullary vasa recta circulation. Before the results of these studies are reviewed, it is important to first appreciate the microvascular anatomy of the renal medulla, as described in detail by others (3,4,40,44,64,(81)(82)(83)127). In brief, it is recognized that blood flow to the medulla of mammalian kidneys is supplied by postglomerular microvessels derived from juxtamedullary glomeruli, the deep glomeruli of the inner cortex that receive their blood supply from the interlobular branches of the arcuate arteries, as described by Kaissling and Kriz (39).…”

From tubular sublimate nephropathy via urinary concentrating mechanism to glomerular disease—Wilhelm Kriz’s contribution to modern nephrology

“…[26,28,36,54]. Crucially, important work on the general structure of the mammalian kidney was done together with Hermann Koepsell, who later became chair of the department of anatomy in Würzburg, and long-standing collaborator and congenial morphologist Brigitte Kaissling, who left Heidelberg in 1982 for stays in Yale, Basel, and her final destination of Zurich.…”