Fig. 1

Effect of increased or decreased medullary solute concentration in rats. a Compared to the initial body weights and to controls, both water restricted and furosemide treated rats had significantly lower body weights at harvest. The urine volume dropped by 50% due to water restriction, but increased almost 2-fold in furosemide treated rats, accompanied by significantly decreased or increased excretion of solutes, respectively. b Water restriction increased mRNA expression of TGF-ß by 2-fold in the medulla, accompanied by marked TGF-ß immunostaining c, d, as compared to control and furosemide treated rats. d The cytoplasm of outer medullary tubular epithelial cells were negative in controls and only weakly stained in furosemide treated rats, but no interstitial staining was observed. However, water restriction increased the cytoplasmic TGF-ß staining intensity in several tubular cells in the inner stripe of the outer medulla (red cytoplasm, see arrows). In contrast, TGF-ß immunostaining showed mostly interstitial staining in the inner medulla of controls and furosemide treated rats, but also tubular cytoplasmic staining in water restricted rats (see insets, arrows pointing on positive cells). Primary antibody was omitted as negative control for immunostaining. Data are presented as mean ± SEM, n = 6/group. * p < 0.05, ** p < 0.01, *** p < 0.001 (one-way ANOVA with Tukey’s post-hoc test or Kruskal-Wallis test with Dunn’s post-hoc test)