Changes of sodium and urea concentrations in the renal papillary interstitial fluid on dehydration of rats

Abstract

1. The isolated renal papillae of a rat were centrifuged in a two tube assembly which allowed fluid from the tissue to separate into the lower tube.2. The papillae were centrifuged for 15 min at 300 g and 1500 g consecutively.3. After intraperitoneal injection of Na 131I‐diatrizoate, the activities of urine, and fluid samples obtained from the papilla, were compared. It was found at 1500 g that the median value for papillary fluid activity was 1·52% of the activity of urine. This is evidence that the papillary fluid was virtually free from any contamination from the terminal collecting ducts.4. It is considered that the fluid sample obtained from the papillae by centrifugation at 1500 g is a representative and reproducible sample of interstitial fluid.5. The method was used to demonstrate changes in solute concentrations in the renal papillary fluid, following dehydration of rats.

Osmolality of Renal Cortical Tissue Fluid in Hydropaenic and Diuretic Rats

“…Both renal pedicles were clamped, the kidneys removed and placed on a glass plate; a blood sample was obtained by cardiac puncture and urine was withdrawn from the bladder. Pieces of renal cortex (20-50 mg) were excised and placed under liquid paraffin BP in the upper of two auto analyser pots (Technicon Ltd.), which had small holes (0.5 mm diameter) in its base to permit sep aration of fluid from the tissue [9]. In most cases, sufficient cortical tissue was obtained from each kidney to prepare six such samples, from each of which 20-30 nl of fluid was obtained for separate analysis.…”

“…A relatively new technique, involving cen trifugation of cortical, medullary and papil lary tissue sections, was reported by two groups of investigators to produce fluid which is thought to be mainly derived from interstitial fluid and whose osmolality can be determined cryoscopically [8,9]. Kettyle et al [8] obtained tissue fluid from the cor tex and medulla of rats and dogs using single spin ultracentrifugation of tissue at 30,000 rpm for 30 min at -1 °C.…”

“…Lee and Williams [9] ob tained renal papillary interstitial fluid using centrifugation first at 300 g for 15 min and then at 1,500 g for a further 15 min (both at 1 °C) with separate collection of the two lots of fluid. In the present study, fluid was removed from the tissue by centrifugation using a modification of the method of Lee and Williams [9] and the fluid re-centri fuged (see 'Methods'). Differences in osmolal ity between tissue fluid obtained from hydropaenic rats and from rats in which diuresis had been induced by saline or mannitol were then determined.…”

Compositional Changes of the Corticopapillary Osmotic Gradient during Dehydration in the Absence of Vasopressin

“…Furthermore, the technique of tissue homogenization, as used by Vallin [16], is likely to result in reduced tissue sodium concentrations because of contamination by intracellular(low sodium) fluid; on the other hand, the centrifugation method [7] used by us is believed to recover fluid largely (although not completely) from extracellular sources and, therefore, is more closely representative of interstitial fluid [3,7,10].…”

“…bisected eccentrically, and a column of tissue removed and divided as shown in fig ure 1. The tissue samples from the same zone in the two kidneys were combined and transferred to individual microcuvettes [7] underwater-equilibrated paraffin oil; these cuvettes, which were modified in a manner similar to that described by Lee and Williams [10] to permit better separation of fluid and tissue, were subsequently treated according to the method of Keltyle ct al. [7], After centrifugation for 30 min at 15,000 s and-1 'C, the fluid that had exuded from the tissue was recovered using oil-filled micropipettes and transferred to the bot tom of an oil-filled watch glass.…”