Bowman’s space consists of three interconnected urinary spaces forming drainage pathways for ultrafiltrate (Neal CR et al. 2005, 2007). Glomerular filtrate may enter restrictive urinary spaces under the podocyte cell body (subpodocyte space, SPS) before passing to other urinary spaces. We have measured SPS in 12 week old (early) spontaneously hypertensive rats (SHR) or Wistar Kyoto rats (WKY) controls after fixation at physiological oncotic and hydrostatic pressures. SHR (mean arterial pressure (MAP) 140mmHg) or WKY (MAP 96mmHg) kidneys from pentobarbital (i.p.) euthanased rats were perfusion fixed at matched MAP with isoncotic glutaraldehyde solutions. Serial ultrathin sections of kidney were used to reconstruct regions of glomeruli. From these filtration slit density of the glomerular capillary wall, SPS coverage of the capillaries, and the available area for filtration into the SPS was measured and compared (mean±SEM, unpaired t-test). The filtration slit density along the glomerular filtration barrier in non-SPS regions of the SHR and WKY was the same (2.3±0.2 per µm, n=14, 2.3±0.1 per µm, n=15). However, filtration slit density decreased in the covered SPS regions of SHR glomerular capillaries (1.8±0.1per µm, n=14, P<0.05) compared with WKY controls (2.1±0.1per µm, n=15). The SPS covered area of the glomerular filtration barrier was similar in both (62±14% to 72±9%). Mild hypertension in 12 week old SHR produces a decrease in the number of filtration slits of the filtration barrier covered by SPS. This reduction in filtration pores suggests a lower permeability in these SPS covered regions compared to uncovered regions (non-SPS).