Micropuncture study of renal transtubular concentration gradients of sodium and potassium in adrenalectomized rats

✍ Scribed by K. Hierholzer; M. Wiederholt; H. Holzgreve; G. Giebisch; R. M. Klose; E. E. Windhager

• Publisher: Springer
• Year: 1965
• Tongue: English
• Weight: 1005 KB
• Volume: 285
• Category: Article
• ISSN: 0031-6768
• DOI: 10.1007/bf00362623

✦ Synopsis

Samples of proximal and distal tubular fuid were collected from control rats and from adrenalectomized animals maintained on 0.90/0 NaC1 solution. Plasma and tubular fluid were analyzed for Na 22 afber adequate isotope equilibration and for Na and K by microflamephotometry. Similar analyses were performed in stationary microperfusion experiments in which the magnitude of the limiting concentration gradients for Na and K was estimated. Transtubular electrical potential differences were measured by means of glass-microclcctrodes. A comparison of proximal tubular concentration gradients showed no significant differences between the control and the adrenalectomized rats for either Na or K. In contrast, the ability of the distal tubular epithelium to develop concentration gradients for Na and K was significantly reduced by adrenalectomy. This functional impairment could be reversed by the administration of d-aldosterone. No changes in proximal and distal transtubular electrical potential differences were observed in the various experimental conditions.

On the basis of indirect evidence the site of the action of steroids with mineralocorticoid activity has been placed at various tubular levels. A proximal site has been postulated by NIc~oLsox et al. s°. These investigators found aldosterone to be ineffective in reducing renal sodium excretion after selective lesions in proximal convoluted tubules. On the other hand, data obtained in stop-flow experiments point to a predominant action on more distal parts of the nephron~S,41, 4~. Furthermore,