Proximal luminal volume and fluid reabsorption in the rat kidney

Odd E. Hanssen and the Hanssen method for measurement of single-nephron glomerular filtration rate

In the middle of the twentieth century, the suspicion that deep and superficial nephrons might serve different functions created a demand for measurement of single-nephron glomerular filtration rate (SNGFR). Rather unexpectedly, the answer came from Odd E. Hanssen (1917-1964), a Norwegian physician working on his own in the Department of Pathological Anatomy, University of Oslo, with minimal support and no interaction with renal physiologists. In 1963, after nearly 10 years of work, he presented the ferrocyanide method, allowing simultaneous estimates of SNGFR in a large number of nephrons in all layers of the kidney. This review first describes his early visions of the method and the elaborate and extremely time-consuming studies in mice to verify the technique. As a byproduct came valuable information on the relationship between nephron size and SNGFR, glomerular intermittency, and the emptying of the tubules on filtration stop. Hanssen died from a cerebral hemorrhage in 1964, and for several years the method seemed entirely forgotten. Fortunately, Andrew Baines took up the use of ferrocyanide in 1963-1964 while working on his thesis in Toronto, but his first publication came in 1969 from Saclay, France, in collaboration with Christian de Rouffignac. Modifications allowing determination of absolute SNGFR were worked out by de Rouffignac and by Jaime Coehlo in New York. Thereafter, the "Hanssen method" spread rapidly, and in the early 1980s about 50 reports had been published from 17 laboratories in 9 countries. The distribution of SNGFR in mammals, birds, and fish was described, as well as the response to water and salt loads, vasoactive substances, hormones, varying perfusion pressure, blood loss, etc. Finally, after mentioning two recent methods inspired by the Hanssen technique but using other filtration markers, the review concludes that most of our present knowledge on SNGFR distribution and regulation has been obtained by the method developed by Hanssen 40 years ago.

A study of proximal tubular compliances in normotensive and spontaneously hypertensive rats, and the effect of anaesthesia on the compliance

Proximal tubular compliance (C) was measured in free flow microperfusion experiments from the initial slope of the increase in proximal luminal pressure divided by the step input of volume flow delivered from a microperfusion pipette inserted in a downstream proximal convolution. Five groups of rats were studied: Munich Wistar (WU, n = 11) and Sprague-Dawley rats (SPRD, n = 6) anaesthetized with inactin; and SPRD (n = 11), Wistar Kyoto (WKY, n = 9), and spontaneously hypertensive rats (SHR, n = 11) anaesthetized with halothane. In the inactin groups, C was: 0.309 +/- 0.161 and 0.266 +/- 0.136 nl mm Hg-1, respectively. In the halothane groups, C was: 0.125 +/- 0.023, 0.125 +/- 0.029, and 0.119 +/- 0.0127 nl mm Hg-1, respectively. The means in the inactin groups were significantly higher than those from the halothane groups (P less than 0.001). It is concluded that the choice of anaesthetics has a profound influence on the proximal tubular compliance in the rat, and that the compliance of SHR is equal to that of normotensive rats.

Effects of halothane-nitrous oxide inhalation anesthesia and Inactin on overall renal and tubular function in Sprague-Dawley and Wistar rats

Real function, plasma renin concentration (PRC) and prostaglandin (PG) excretion rate was studied in groups of Sprague-Dawley (SPRD) and Wistar (WIST) rats anesthetized with either Halothane-N2O or Inactin. Conscious rats were used as controls. A. In Halothane-N2O anesthesia inulin clearance (CIN) and absolute proximal reabsorption rate (APR) was moderately decreased (by about 20%), while renal plasma flow (RPF), urine flow and solute excretion remained unchanged as compared to conscious rats. There was a linear relationship between the reciprocal of the proximal occlusion time (OT) and CIN in Halothane anesthesia indicating that the proximal luminal diameter was constant and independent of CIN. B. Inactin anesthesia CIN was similarly reduced but APR was more depressed (by about 35%). RPF and solute excretion rate decreased only in SPRD rats, while urine flow was significantly reduced in both strains. 1/OT was invariant to changes in CIN indicating luminal diameter variations in proportion to CIN. Urinary PGE2-and PGF2 alpha excretion rates and PRC were moderately elevated in operated animals of both strains regardless of the anesthetics used. It is concluded that renal functional parameters in surgically prepared rats are more severely depressed by Inactin than by Halothane-N2O anesthesia. The gas anesthesia is equally well tolerated by both strains of rats.

The effect of carbonic anhydrase inhibition on bicarbonate reabsorption

Renal reabsorption of bicarbonate was studied in Merino ewes during carbonic anhydrase inhibition. Bicarbonate reabsorption was directly proportional to plasma bicarbonate concentration. No tubular maximum for bicarbonate was demonstrated. Elevation of arterial PCO2 or depression of arterial pH caused slight increases in bicarbonate reabsorption. The data suggest that bicarbonate is reabsorbed by 2 distinct processes. The quantitatively more significant process may involve ionic reabsorption of bicarbonate secondary to Na+ reabsorption and a relatively minor part of bicarbonate reabsorption may be secondary to H+ secretion.

The intrarenal distribution of tritiated para-aminohippuric acid determined by a modified technique of section freeze-dry radioautography

Section freeze-dry radioautography has been used to examine the intrarenal distribution of a water-soluble organic acid (para-aminohippuric acid (PAH-3H)) under constant-infusion, steady-state conditions in mouse and rat kidney in vivo. The technique described here has the following advantages: (a) Sectioning and freeze-drying are accomplished in a closed cryostat at temperatures below -40 degrees C; (b) Handling of the section is facilitated by mounting of the section-to-be on adhesive-coated Saran Wrap prior to cutting; (c) Unembedded freeze-dried sections are attached to photographic film at ambient temperature in the dark room; (d) Fixation follows completion of radioautographic exposure and precedes photographic development; (e) Permanent close contact is maintained between tissue and film. Morphologic preservation compared favorably with that obtained by optimal fixation techniques, which, however, permit diffusion. Cellular accumulation of PAH-3H during secretion was demonstrated in the proximal tubule under steady-state conditions in vivo. The cellular concentration of PAH-3H was uniform throughout the length of the proximal tubule in mouse and rat kidney.

Renal tubular flow dynamics during angiotensin diuresis in the rat

1. Tubular size and lissamine green transit times were measured in rat kidneys undergoing a diuretic response to angiotensin II (0.5 mug/kg per min), and compared with the changes observed during diuresis induced by osmotic diuretics, noradrenaline and chlorothiazide.2. Angiotensin always caused a marked prolongation in proximal and distal tubular transit times; individual distal convolutions were coloured for prolonged periods, and lissamine green appeared in high concentration in distal tubules.3. Marked changes were observed in superficial tubular calibre during a stable diuretic response to angiotensin. Where distal tubular diameter was normal for the rate of urine flow, proximal tubular volume was generally reduced. In a number of experiments, however, distal tubules were markedly dilated, and in these cases proximal tubular volume was also often increased. Angiotensin may therefore be capable of causing a degree of internal hydronephrosis in the rat kidney.4. Prolongation of dye transit times, and the appearance of a concentrated lissamine green bolus in distal tubules, was suggestive of a decreased superficial nephron flow rate, indicating that the diuretic effect of angiotensin may take place only through deeper nephrons.