Action of Aldosterone on Cultured Renal Collecting Duct Cells during the Latent Period

Abstract

The effects of aldosterone on protein synthesis in the latent period were investigated on cultured renal collecting duct cells from neonatal rabbit kidneys. Tissue was incubated with radioactively labelled uridine and amino acids and then precipitated with trichloroacetic acid in order to determine the intracellular precursor pool and identify new synthesis of RNA and protein. During the latent period, aldosterone increased the intracellular radioactive uridine pool and total radioactive RNA content already 20 and 60 min after its application; conversely 40 min after aldosterone introduction, no stimulation was found. Further experiments revealed that the intracellular radioactive amino acid pool was generally increased by aldosterone after 20, 40 and 60 min, while a distinct increased radioactive protein content was found to be induced by aldosterone only after 40 min. This indicates that aldosterone increases the uptake of RNA and protein precursors and the new synthesis of RNA and proteins. These events seem to to be regulated not continously but intermittently. The induced proteins possibly take part in the mediation of the early hormone response. Experiments with the aldosterone antagonist, spironolactone, provide evidence for the specificity of the described hormone effects. The results after application of the Na⁺ channel blocker, amiloride, and the Na⁺/K⁺-ATPase inhibitor, G-strophanthin, indicate that the aldosterone effects are controlled by Na⁺ channels and Na⁺ pumps and therefore by the intracellular Na⁺ content. The inhibitory effect of cycloheximide on the aldosterone-induced protein synthesis indicates the role of these proteins on the hormone-stimulated Na⁺ transport.

Evidence for a gastrointestinal–renal kaliuretic signaling axis in humans

“…Furthermore, we observed the kaliuresis within the first hour following Meal+KCl and there is generally considered to be a latent period of 1-2 h between aldosterone stimulation of mineralocorticoid receptors and consequent effects on tubular transport. [30][31][32] Most important, we replicated the Meal+KCl experiment following aldosterone blockade with 400 mg of eplerenone. We again observed a substantial kaliuresis and cumulative potassium excretion, indicating that this result is independent of both serum potassium concentration and aldosterone.…”

Rapid activation of KATP channels by aldosterone in principal cells of frog skin.

“…The short-term hormonal effect on single K+ channels, which must be non-genomic, was also observed on the macroscopic scale as an increase in total basolateral membrane K+ conductance in a nystatinperforated epithelium. Recent studies in kidney have described acute effects of aldosterone (with a latency of <30 min) on intracellular pH Cooper & Hunter, 1994), Na+-K+-ATPase activity (El Mernissi & Doucet, 1983), RNA synthesis (Zwanzig, Minuth & Gross, 1990) and transepithelial potential difference (Gross & Kokko, 1977). A much more rapid activation (<10 min) of Na+-H+ exchange has also been shown to underlie aldosterone-induced cell swelling in lymphocytes (Wehling et al 1991 (Maguire, O'Sullivan & Harvey, 1994).…”

Potassium Transport in the Cortical Collecting Duct

“…Very similar to the activation o f N a+ reabsorption in the CCD by aldosterone [26,40], the secretion o f K + is also stimulated by this hormone [21,22,40], The effect of aldoste rone includes in an early phase (within I h) an activation of existing ion channels and the N a+-K +-ATPase [41][42][43][44] and in the later phase (after several hours to days) a synthesis of new channels, pump molecules and mitochondrial enzymes [41,[43][44][45]. Another hormone, adiuretin (ADH.…”