Afferent arteriolar diameter in DOCA-hypertensive and post-DOCA hypertensive rats estimated by means of microspheres

Intrarenal pressure and sodium excretion in hypertension of chronic glomerulonephritis in humans

The relationship between the fractional excretion of filtered sodium (FENa) and the peritubular capillary physical factors (PCPF) in the hypertension (HT) of chronic glomerulonephritis (GN) was examined in hydropenia (C) and during sustained isotonic saline volume expansion (E; 3% net increase of body weight) in 32 GN patients (16 with HT), and compared with our previous findings in 20 normal individuals (NORM) and 19 patients with essential hypertension (EH). Fourteen GN patients (seven with HT) had a 75% reduction of glomerular filtration rate (GFR), the others (nine with HT) had normal or near normal GFR. The PCPF were estimated from the intrarenal venous (wedged) pressure (IRVP) and the calculated efferent arteriolar protein concentration (EAPC). In C, IRVP correlated to GFR (r = 0.682, p less than 0.001) and (FENa) (r = -0.357, p less than 0.05), but IRVP and EAPC were similar in HT and normotension at comparable levels of GFR. The increase of FENa during E (delta FENa) was exaggerated in all HT groups even at reduced levels of GRF, and could not be related to changes in renal hemodynamics or PCPF. delta FENa correlated with mean arterial pressure in C both in GN (r1 = 0.702, p less than 0.01) and in the combined NORM/EH group (r2 = 0.478, p less than 0.01), with r1 greater than r2 (p less than 0.005). The findings indicate that the pathogenesis of hypertension of chronic glomerulonephritis is independent of changes in the PCPF, and are compatible with the idea that humoral factors are the main mediators of the altered sodium excretion during saline volume expansion in the HT of both chronic GN and EH.

Renal afferent arteriole in the spontaneously hypertensive rat

We conducted morphometric studies on the afferent arteriole of spontaneous hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats to gain a better understanding of its changes with the development of hypertension. Differences may be related to the SHRs' increased renal vascular resistance. Methacrylate vascular casts were made of the renal vasculature after perfusion fixation with glutaraldehyde. These vascular casts were then examined and measurements made with the scanning electron microscope. Results from this examination of the scanning electron microscope demonstrated a smaller afferent arteriolar diameter in the SHR, compared to the WKY, for both the inner and outer cortical glomeruli. This difference was seen in the 6-week-old SHR, prior to a statistically different blood pressure from the WKY controls, as well as in the 12-week-old hypertensive SHR. However, this afferent diameter difference between rat strains was more pronounced in rats at 12 weeks of age. The tapering of the afferent arteriole (difference between proximal and distal afferent diameters) was greater in the 12-week-old SHR than in the age-matched WKY or 6-week-old SHR. We conclude that the smaller caliber afferent arterioles of the SHR may predispose and play a role in the pathogenesis of the subsequent hypertension. The increased afferent arteriolar tapering seen in the hypertensive SHR relates to the already present increased blood pressure. Wall thickness/radius ratios are not different between rat strains (SHR and WKY) at either 6 or 12 weeks of age. These results suggest increased vascular constriction or hypoplastic vessels as the cause of the smaller caliber vessels in the SHR rather than increased wall thickness.