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 pa irs or branched sequentially along the same arcuate arterial branch (A rcB). With blood-perfused juxtamedullary nephron (JMN) preparations, A R were elicited by raising blood perfusion pressure from 60 to 120 mmH g 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 a nd short AA at juxtaglomerular or early AA (EAA) sites. Sequentially b ranched 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 A A or ArcB sites. In both AA branching patterns, EAA and nearby sites o f the feed arteries had similar AR. Hence, our results are consistent with hemodynamic coupling in paired JMN. Around branching sites, AR ar e spatially organized in a way consistent with electrotonic vascular c oupling.