Mechanisms of hormonal modulation of ion transport in the toad's urinary bladder. Subcellular localization of aldosterone-induced proteins.

A dual-label isotope technique was used to study the effects of aldosterone upon the incorporation of amino acids into proteins of the in vitro toad urinary bladder. Following labeling, the mucosal cells were disaggregated and the mitochondria-rich and granular cells were separated. Proteins with an elevated isotope ratio were found in a plasma membrane fraction (170 000, 110 000 and 85 000 daltons) and in the cytosol (36 000 and 6 000 daltons) of the preparations enriched in mitochondria-rich cells. These effects of aldosterone were blocked by cycloheximide. There was no evidence that aldosterone had induced the incorporation of labeled amino acids into carbonic anhydrase isolated from the soluble fraction by affinity chromatography. The results suggest that the physiologic response of the toad bladder to aldosterone is related to the synthesis of both soluble and plasma membrane proteins.