Fig. 3.

Effects of 3-OHB on isolated coronary resistance arteries. The vasorelaxant responses in panel A through G are shown relative to a stable U46619-induced pre-contraction. A, 3-OHB-induced changes in coronary artery tone (n = 6). B, concentration-dependent vasorelaxant responses of coronary arteries to 3-OHB (n = 8). Na-3-OHB was substituted for NaCl and tested by successive full exchanges of the bath solution. The relaxant response was calculated relative to time control experiments where arteries were repeatedly washed to PSS without 3-OHB. In both cases, the concentration of U46619 was kept constant at the pre-contraction level. C+D, effects of D-3-OHB (C, n = 5–8) and L-3-OHB (D, n = 4–7) on coronary artery tone. In both cases, Na-3-OHB was compared to equimolar extra NaCl. E, assessment of vasorelaxation induced by 5 µM acetylcholine under control conditions (n = 8) and following endothelial denudation of coronary septal arteries (n = 6). F+G, 3-OHB-induced vasorelaxation in coronary arteries without functional endothelium (F, n = 6) and in intact arteries treated with 3 µM of the non-selective cyclooxygenase inhibitor indomethacin (G, n = 5). Na-3-OHB was compared to equimolar extra NaCl. H. U46619-induced contractions of coronary arteries in presence of Na-3-OHB or equimolar extra NaCl. Vessels were exposed to cumulative stepwise increases in U46619 concentration, and contractions—relative to the initial maximal contraction to 120 mM extracellular K⁺ and 0.1 μM U46619—were fitted to sigmoidal functions (n = 6). Bars and symbols represent mean±SEM. Data in panels A, C, D, F, and G were compared by repeated-measures two-way ANOVA (interaction) or, in case of missing values, by mixed-effects analysis. In panel B and H, data were fitted to sigmoidal functions. In panel E, data were compared by unpaired two-tailed Student’s t-test; in panel H, by extra sum-of-squares F-test