ANATOMIC PAIRING OF AFFERENT ARTERIOLES AND RENIN CELL DISTRIBUTION IN RAT KIDNEYS

Close afferent arteriolar (AA) connectivity is a prerequisite for hemo dynamic interaction between superficial rat nephrons. Studies were con ducted in rat, mouse, rabbit, and human renal vasculatures obtained by an HCl maceration-microdissection technique to document the extent of AA connectivity. In rat kidneys, we assessed the possibility for a sl ow component of internephron coupling, as reflected by arteriolar reni n cell distribution after specific immunostaining for renin. In the fo ur species examined, 51% (human) to 60% (mouse) of total AA population s were organized as vascular units consisting of mostly two AA sharing a common origin and a connecting arterial segment. In rat AA pairs, b ranch lengths were significantly correlated, suggesting coordinated ar teriolar growth. The sum of AA branch lengths averaged 278 +/- 6 mu m. Rat arteriolar renin status, ranging from no renin cells to renin-rec ruited midafferent arterioles, distributed in a significantly nonrando m fashion within AA pairs, and 52% of the pairs had equal renin status . Hence, AA pairing is a consistent anatomic characteristic of mammali an kidneys and may constitute an optimal vascular design for hemodynam ic as well as endocrine interactions.