Alteration in the labelling of renal ribosomal protein by aldosterone

Abstract

The present study is an investigation of the effect of aldosterone on the relative extents of labelling of the renal cortical ribosomal proteins from adrenalectomized rats. It was noted that between 30 and 90 min of incubation of the renal cortical slices at 37°C with radioactive leucine (between 2.5 and 3.5 h following aldosterone administration to the adrenalectomized animals) the hormone did not alter the extent of labelling of the total ribosomal protein population. On the basis of double-isotope labelling it was found that 3.5 h following aldosterone administration there was a relative decrease in the extent of labelling of a renal cortical ribosomal protein(s) whose molecular weight was between 57,000 and 62,000. This decrease in labelling could be due to either a decreased synthesis or a decreased exchange of the ribosomal protein(s). When the rats were first pretreated with actinomycin d the effect of aldosterone on the ribosomal protein(s) was lost. Also, the administration of dexamethasone alone to the adrenalectomized animals did not alter the [ 3H/ 14C] ratios of the ribosomal protein(s). This molecular alteration may be physiologically significant since we had found earlier that the functional capacities of these same ribosomes were increased 3.5 h after aldosterone treatment, and since pretreatment of adrenalectomized animals with actinomycin d is known to abolish the antinatriuretic effect of aldosterone while dexamethasone has no sodium retention activity at all on adrenalectomized animals.