Effects of a Nucleoside Transporter Inhibitor, Dilazep, on Renal Microcirculation in Rats.

Visualisation of the Effects of Dilazep on Rat Afferent and Efferent Arterioles In Vivo

“…The presence of A2 receptors on preglomerular microvessels is less clear (33). Kawabata et al have shown that dilazep dilated the efferent arterioles and attenuated tubuloglomerular feedback (TGF)-induced afferent arteriolar vasoconstriction in clearance and micropuncture experiments (6). It is unlikely that afferent arteriolar vasodilatation is flow-induced, since, in the present study, there was no difference in the course of vasodilatation between the afferent and efferent arterioles.…”

“…Yukimura et al examined dilazep-induced changes in renal flow in dogs and showed that the renal vascular effects of dilazep may be exerted by augmentation of endogenous adenosine and mediated through adenosine receptors (5). Kawabata et al have also reported in their clearance and micropuncture study that extracellular adenosine augmented by dilazep dilated both afferent and efferent arterioles, probably via A2 receptors (6). As the coronary vasodilator dilazep augments endogenous adenosine actions, it may aid in elucidating the physiological roles of adenosine in renal haemodynamics.…”

Effects of Uroguanylin, an Intestinal Natriuretic Peptide, on Tubuloglomerular Feedback

“…As previously shown by micropuncture experiments in our (15,16) and other laboratories (17), the perfusion of agents into the tubular lumen allows them to reach sites adjacent to the nephron, including the vascular component in the juxtaglomerular apparatus (JGA), i.e., the effector cells of TGF.…”

Adenosine and Kidney Function

“…In the latter condition, chronic dipyridamole treatment not only normalized maximum TGF responses but also prevented glomerular hyperfiltration and lowered proteinuria (347). However, inhibitors of nucleoside transporters could also inhibit TGF by increasing extracellular adenosine concentrations to levels that activate vasodilatory adenosine A 2 receptors in the afferent arteriole (156,327) and/or by possibly reducing the release of adenosine from macula densa cells (see below). Thus the effect of this kind of agent on TGF is not predictable.…”