Diameter of the Afferent Arteriole in the Dog Kidney Estimated by the Microsphere Method

Abstract

Microspheres with diameters of from 10 to 30 mum were injected into the renal arteries of three anesthetized dogs. The six kidneys were studied by light microscopy. The diameters of the spheres trapped in the afferent arterioles and of all spheres recovered in the kidneys were recorded. On the basis of the distribution of diameters in these two populations of spheres, the average diameter of the afferent arteriole and the distribution of the afferent arteriolar diameters were estimated. The average diameter of the afferent arterioles was 16.3 mum (S.D. 2.2 mum), without any difference between three cortical layers of equal thickness. The mean diameter of spheres trapped in the interlobular arteries was 25.7 mum (S.D. 2.6). It is suggested that the pressure drop along some interlobular arteries may be of physiological importance, affecting the autoregulation of blood flow in the renal cortex.

Diameter of afferent arterioles during autoregulation estimated from microsphere data in the dog kidney.

“…The discrepancy between the estimated mean diameter values for the afferent arteriole presented here and that derived from the diameter of the microsphere trapped in the afferent arterioles 4 may be explained by the presence of some small nonoccluding microspheres trapped behind larger ones. The present regression model is not as sensitive to this special effect as the method published earlier which gave slightly lower diameter values.…”

“…To account for possible axial streaming effects in addition to pure geometrical exclusion, f(p,r) may be chosen somewhere between the geometrical exclusion factor and Ferry's correction factor, 5 ' 7 tentatively f(p,r) = 1 -p/r) y ; 0 < p < r ); otherwise (4) where y has to be determined; y = 0 corresponds to the case with pure geometrical exclusion.…”

“…The error ei in the model The advantage of the formula in Equation A.3.6 instead of the commonly used (£7f) 4 becomes clear when noting that small errors in the estimation of f' and f may give rise to great errors in the conductance ratio. In the regression analysis, however, these errors will be counterbalanced by corresponding shifts in the k', k values.…”

“…For this purpose we used an original version of the microsphere method, the principle of which is to record the diameter population of the spheres which become trapped in (or pass through) the afferent arterioles and the population of sphere diameters presented to these vessels. 4 ' 5 Methods Mongrel dogs of either sex (body weight, 17-25 kg) were anesthetized with sodium pentobarbital (25 mg/kg given intravenously as an initial dose), and N 2 O was supplied by conventional anesthetic apparatus connected to an endotracheal tube. The arterial oxygen saturation, pH, and Pco 2 were within normal limits during the experFrom Medical Department A, University School of Medicine, Bergen, Norway.…”

Intrarenal vascular resistance in glycerol-induced acute renal failure in the rat.

“…Thus, preglomerular vasoconstriction is still a viable hemodynamic explanation for the decreased GFR of acute renal failure. To test this hypothesis, we measured afferent arteriolar diameter in glycerol-induced acute renal failure, using a recently developed microsphere method (Chenitz et al, 1976;Ishikawa and Hollenberg, 1977;Ofstad et al, 1975). …”