3 Glomerular permeability is not affected by heparan sulfate glycosaminoglycan deficiency in zebrafish embryos 55 n = 14; p=0.75 versus WT and p=0.39 versus homozygous dak/ext2). As small particles can pass readily through the GFB, the similar number of 3-kDa dextran droplets indicates fully functional tubular reabsorption in all groups. We also found no significant difference between homozygous dak/ext2 mutants and WT embryos with respect to 70-kDa dextran particles (the mean number of droplets was 8.56, SD 5.33, n = 32 and 9.27, SD 3.72, n = 21 respectively; p=0.59) However, WT PAN-injected embryos had significantly more 70-kDa droplets (16.93, SD 5.41, n = 14) compared to both WT embryos (p<0.0001) and dak/ext2 mutants (p<0.0001). Taken together, these data indicate that 70-kDa particles pass the GFB in similar quantities under physiological conditions and in an HS-GAG-free environment. Figure 3. Homozygous dak/ext2 mutant zebrafish have normal glomerular permeability and tubular reabsorption capacity Panels A and B show transverse sections through the proximal tubular epithelium of homozygous dak/ext2 mutant embryos injected with red fluorescent 3-kDa dextran (A) and green fluorescent 70-kDa dextran (B). The white ellipse highlights the proximal tubule epithelial cells. The bright area between the circle reflects background fluorescence, partly due to auto-fluorescence. (C and D) Summary of the number of 3-kDa (C) and 70-kDa (D) dextran droplets in wild-type, homozygous dak/ext2 mutant, and PAN-injected wild-type embryos. ns, p>0.05 versus wild-type; ****p<0.0001 versus wild-type. A digital high-pass filter has been placed over panels A and B to enhance the contrast between reabsorption droplets and the surrounding tissue. Scale bar = 5 µm.
RkJQdWJsaXNoZXIy MTk4NDMw