Branching patterns and autoregulatory responses of juxtamedullary afferent arterioles.

The spatial organization of autoregulatory responses (AR) was assessed in couples of afferent arterioles (AA), either grouped as anatomic pairs or branched sequentially along the same arcuate arterial branch (ArcB). With blood-perfused juxtamedullary nephron (JMN) preparations, AR were elicited by raising blood perfusion pressure from 60 to 120 mmHg and quantified by videomicroscopy as pressure-induced constrictions. Paired AA had unequal lengths (long-to-short ratio, 1.9 +/- 0.1; n = 36); however, no statistical difference in AR was found between long and short AA at juxtaglomerular or early AA (EAA) sites. Sequentially branched AA had the same length heterogeneity as paired AA (proximal-to-distal AA length ratio, 2.0 +/- 0.2; n = 30). However, AR exhibited a significant axial gradient, being higher in distal than in proximal AA or ArcB sites. In both AA branching patterns, EAA and nearby sites of the feed arteries had similar AR. Hence, our results are consistent with hemodynamic coupling in paired JMN. Around branching sites, AR are spatially organized in a way consistent with electrotonic vascular coupling.