[Effect of furosemide on the hemodynamics of the kidney medulla during salt depletion].

Unlabelled: In sodium depleted rats cortical and medullary blood flow was studied before and after 4-chloro-N-(2-furylmethyl)-5-sulfamoyl-anthranilic acid (furosemide). 86Rb was used as an indicator of renal hemodynamics. Its activity was assessed in systemic blood and in tissue slices of the kidney. At the beginning of the experiments the animals were loaded p.o. with 1.3 ml/100 g b.w. of isotonic saline. 3 h later a rapid i.v. injection of 50 muCi (=5.6 MBq) 86Rb was given to 12 control and 9 furosemide treated animals.

Results: After 0.7 mg/100 g b.w. of furosemide the sodium and water excretion rises to 820% and 860% resp. (p less than 0.0005). Systemic body hematocrit increases from 47 to 49%. The renal cortical blood flow is not influenced by furosemide. Compared with controls there is a decrease in blood flow through the outer medulla from 1.57 +/- 0.65 to 1.00 +/- 0.37 ml/g.min, through the inner medulla from 0.75 +/- 0.30 to 0.59 +/- 0.23 ml/g.min, and through the papillary tips from 0.85 +/- 0.40 to 0.46 +/- 0.18 ml/g.min. However, these hemodynamics changes are not significant. It is concluded that the decrease in renal medullary hemodynamics of furosemide-treated rats is due to a stimulation of the renin-angiotensin system.