Effects of glucocorticoid administration on urinary albumin excretion by the normal kidney

In an effort to elucidate mechanisms by which glucocorticoids enhance urinary protein excretion, albumin and lysozyme excretion patterns were studied in normal rats which had been subjected to a variety of experimental protocols. On the basis of these studies the following conclusions were reached: (1) The acute administration of glucocorticoids produces an immediate increase of both glomerular filtration rate (GFR) and of urinary albumin and lysozyme excretion rates. (2) A delayed albuminuric response to glucocorticoids occurs 14-32 h after drug administration. This second period of albuminuria is quantitatively far more significant than the acute albuminuric response and it occurs at a time when GFR is not statistically different from control experimental animals. (3) Lysozyme excretion 14-32 h following glucocorticoid administration is normal, suggesting an intact tubular protein reabsorption mechanism at the time of maximal albuminuria. (4) The delayed albuminuric period cannot be acutely reproduced by infusion of 5 ml of serum harvested from dexamethasone pretreated albuminuric rats. (5) Dietary Na intake (and presumed activity of the renin/angiotensin axis) does not appear to influence the magnitude of the glucocorticoid-induced albuminuric reaction. Further work is needed to more fully delineate the pharmacologic pathway by which glucocorticoids affect urinary protein excretion and to ascertain whether this response differs between the normal and pathologic kidney.