[The effect of furosemide and hypertonic mannitol on the corticomedullary albumin gradient of the rat kidney (author's transl)]

[Comparison of the effects of gastroenteric and parenteral saline loading on kidney function after inhibition of prostaglandin synthesis (author's transl)]

We inhibited the prostaglandin synthesis with indomethacin in rats during a 7-h (periods: 1--4h; 4--5.5h; 5.5--7h) gastroenteric and parenteral infusion of isotonic saline. Indomethacin was given in a dosis of 10 mg/kg of b. wt. by stomach tube after 5.5-h infusion of saline. We studied how far prostaglandins are involved in the different function of the kidney by measuring the water and sodium excretion and the cortico-medullary osmotic and albumin concentrations of the kidney.

RESULTS

1. a) Studies Without Indomethacin. As compared to infusion of isotonic saline into the stomach water excretion is decreased by 30% (P less than 0.02) and 35% (P = n.s.) in the second and third 90 min period during parenteral infusion of saline. As compared to gastroenteric infusion we found an increase of the total osmolarity by 13% (P less than 0.02) in the cortex of the kidney. b) Studies with Indomethacin. As compared to saline infusion into the stomach indomethacin-treated rats decrease their urinary flow rates in 90 min by 26% (P = n.s.) in the presence of equivalent saline infusion into the aorta. Total osmolarity of the parenteral loaded rats increases by 17% (P less than 0.01) in the cortex of the kidney. 2. Indomethacin leads to an increased concentrating ability of the kidney in both gastroenteric and parenteral loaded rats. 3. In the presence of indomethacin plasma albumin of the kidney increases in the cortex and in the outer medulla of the kidney. In the inner medulla, and in the papillary tip, however, albumin concentration decreases significantly. As compared to gastroenteric saline infusion, the osmolarity of the kidney tissue increases and the urinary flow rate decreases during equivalent parenteral infusion of isotonic saline. The prostaglandins are not responsible for the pronounced diuresis during infusions of isotonic saline into the stomach.

The extravascular pool of albumin in the non-diuretic rat kidney estimated by means of radioactive tracers and quantitative immunochemistry

The extravascular pool of albumin in the non-diuretic rat kidney was determined as the difference between total and intravascular albumin pools. The total pool of albumin was determined in two ways in the same kideny: 1. as the distribution volume of rat endogenous albumin measured immunochemically and 2. as the distribution volume of 125I-labelled rat albumin equilibrated for 4 days. The distribution volume of 131I human albumin after 1 min equilibration was taken as a measure of the intravascular pool. Total albumin pool estimated as rat endogenous albumin volume of distribution averaged 13.4, 25.1, and 43.0 mul per 100 mg tissue in cortex, outer and inner medulla, respectively. Similar figures were obtained using 125I-labelled rat albumin. Intravascular pool of albumin in the 3 zones averaged 7.2, 19.7, and 26.8 mul per 100 mg tissue. The calculated extravascular fraction of albumin averaged 0.44, 0.21, and 0.35 for cortex, outer and inner medulla, respectively.