Intra- and extrarenal arteries exhibit different profiles of contractile responses in high glucose conditions

Abstract

Background and purpose: The renal artery (RA) has been extensively investigated for the assessment of renal vascular function/dysfunction; however, few studies have focused on the intrarenal vasculature.

Experimental approach: We devised a microvascular force measurement system, which allowed us to measure contractions of interlobar arteries (ILA), isolated from within the mouse kidney and prepared without endothelium.

Key results: KCl (50 mM) induced similar force development in the aorta and RA but responses in the ILA were about 50% lower. Treatment of RA with 10 microM phenylephrine (PE), 10 nM U46619 (thromboxane A(2) analogue) or 10 microM prostaglandin F(2 alpha) elicited a response greater than 150% of that induced by KCl. In ILA, 10 nM U46619 elicited a response that was 130% of the KCl-induced response; however, other agonists induced levels similar to that induced by KCl. High glucose conditions (22.2 mM glucose) significantly enhanced responses in RA and ILA to PE or U46619 stimulation. This enhancement was suppressed by rottlerin, a calcium-independent PKC inhibitor, indicating that glucose-dependent, enhanced small vessel contractility in the kidney was linked to the activation of calcium-independent PKC.

Conclusion and implications: Extra- and intrarenal arteries exhibit different profiles of agonist-induced contractions. In ILA, only U46619 enhanced small vessel contractility in the kidney, which might lead to renal dysfunction and nephropathy through reduced intrarenal blood flow rate. A model has been established, which will allow the assessment of contractile responses of intrarenal arteries from murine models of renal disease, including type 2 diabetes.

Figure 1

Agonist-induced contractile responses in endothelial-denuded renal (RA) and interlobar (ILA) arterial rings. Isometric force development in RA (a) and ILA (b) was measured under resting tension of 400 μN. Upon detection of a maximal response to 50 mM KCl, each contractile agonist, 10 μM phenylephrine (PE); 100 nM U46619 (U46619); 10 μM PGF_2α (PG); or 1 μM angiotensin II (Ang) was applied at 37 °C for 5 min and representative recordings shown. In (c), data are summarized, relative to responses to 50 mM KCl (% 50 mM KCl). Each value represents the mean±s.e.m. of five independent determinations. ^*P<0.01 from KCl-induced response; ^#P<0.01 from response in RA.

Figure 2

Phenylephrine (PE)-induced force development in endothelial-denuded renal (RA) and interlobar (ILA) arterial rings under normal and high glucose conditions. Representative recordings of force development in RA (a) and ILA (b) are presented. Concentration–response relationships for PE-induced isometric force responses in RA and ILA were calculated as % of the maximal response in normal physiological salt solution (PSS) (c). Vascular tissues were pre-incubated under normal and high glucose conditions at 37 °C for 30 min. Each value represents the mean±s.e.m. of five independent determinations. ^*P<0.01 vs responses in normal PSS.

Figure 3

U46619-induced force development in endothelial-denuded renal (RA) and interlobar (ILA) arterial rings under normal and high glucose conditions. Representative recordings of force development in RA (a) and ILA (b) are presented. Concentration–response relationships for U46619-induced isometric force responses in RA and ILA were indicated as % of the maximal response in normal physiological salt solution (PSS) (c). Vascular tissues were pre-incubated under normal and high glucose conditions at 37 °C for 30 min. Each value represents the mean±s.e.mean of five independent determinations. ^*P<0.01 vs responses in normal PSS.

Figure 4

Effect of rottlerin (1 μM), a calcium-independent PKC inhibitor, on the increase in agonist-induced force development stimulated by high glucose conditions in endothelium-denuded renal (RA) (a) and interlobar (ILA) (b) arterial rings. Isolated vascular tissues were pre-incubated under normal and high glucose conditions and stimulated with either 3 μM phenylephrine (PE) or 10 nM U46619. Rottlerin (1 μM) was added 10 min before agonist stimulation. ^*P<0.01 vs unstimulated resting level; ^#P<0.01 vs responses in normal physiological salt solution (PSS).

Figure 5

Schematic diagrams illustrating responses of intra- and extrarenal vessels under normal and high glucose conditions. (a, b) Phenylephrine (PE)- and (c, d) U46619-induced contractile responses in RA and ILA under normal (a, c) and high glucose (HG) (b, d) conditions are illustrated.