The Quantitative Estimation of Perfusible Glomeruli and the Collagen and Non-Collagen Nitrogen of the Normal Kidney

Abstract

A technique has been developed for the quantitative estimation of perfusible glomeruli in the normal and diseased kidney. This technique is a modification of that originally described by Cook and Pickering (5). It entails the perfusion of the intact or excised kidney under standardized conditions with magnetic oxide of iron, which specifically localizes in the glomerular capillaries. The kidney is then emulsified and ground through a 100-mesh copper wire sieve and passed through an electromagnetic field. The magnetized glomeruli adhere to the glass under the influence of the magnetic field, the rest of the suspension passing through. The suspension is run through the electromagnetic field four or five times with the recovery of at least 90% of the glomeruli. The glomeruli are suspended in 30% aqueous solution of PVP and counted under microscopic vision on a scored glass microscope slide. The perfusible glomeruli and creatinine clearance of rats, ages 1 to 18 months and rabbits, ages 1 week to six months, have been determined and indicate that in the rat there is no increase in glomerular counts with maturation (mean 3.78 × 10⁴); GFR per glomerulus reaches the adult level by four weeks. In the rabbit the number of perfusible glomeruli increased from 5.5 × 10⁴ at one week to the adult level of 19.3 × 10⁴ at 1 month. There is a progressive increase in GFR per glomerulus from one week through six months, thus indicating the pattern of structural and functional maturation of the glomerulus in rat and rabbit. The collagen and non-collagen nitrogen in these animals was also studied. The techniques appear applicable to the study of the diseased kidney.

Platelets mediate neutrophil-dependent immune complex nephritis in the rat.

“…Counts per minute of 251-anti-Con A were converted to gg total antiCon A antibody per 38,000 glomeruli (the average number of glomeruli present in a rat kidney [27]) based on the specific activity of 1251I anti-Con A preparations.…”

Control of fluid absorption in the renal proximal tubule

“…In view of the importance of the kidneys in controlling body water and salt content, the nature of Received for publication 29 January 1968 and in revised form 5 April 1968. the renal regulatory mechanisms involved is of considerable interest. From the results of numerous investigations of this subject it is apparent that a multiplicity of factors are involved which may not be readily separable.…”

Experimental Membranous Glomerulonephritis in Rats

“…The reason for this discrepancy between TKAb and GAb is unclear. Our calculations of GAb assume 38,000 glomeruli per rat kidney (24,25). Calculations based on a larger number of glomeruli per rat kidney (24,25) could slightly reduce this discrepancy between TKAb and GAb, but there remains a significant amount of antibody apparently bound to extraglomerular renal structures or trapped in the interstitial space that is not readily appreciated by IF (40).…”

“…The GAb of each rat was calculated from the equation: GAb (micrograms per two kidneys) = counts per minute in glomeruli x 76,000/number of glomeruli x specific activity, where 76,000 = number of glomeruli in two rat kidneys (24,25). When glomeruli were isolated from the perfused kidneys of rats given normal sheep IgG, nonspecific contamination of glomeruli with sheep IgG was found to be <1 g.g/2 kidneys at all time intervals and has therefore been disregarded in the determination of GAb.…”