Hormonal control of renal potassium excretion

Hormonal regulation of potassium excretion by the kidney is generally thought of principally as a function of aldosterone. However, recent studies not only redefine the role of aldosterone in this regard but suggest that other hormones may also contribute toward maintenance of potassium homeostasis by the kidney under a variety of physiological conditions. This review will survey what is known of these humoral influences, emphasizing both the specific effect of each agent on renal tubular potassium transport, as well as the possible homeostatic role played by each in maintaining potassium balance under physiological conditions. The limits of the present article are that only hormones extrinsic to the kidney will be considered, leaving aside the possible effects of intrinsic renal hormones, about which less specific information is available.The hormonal actions to be discussed will be considered within the framework of our current conceptions of renal potassium handling [1, 2]. It is thought that potassium is filtered freely and undergoes extensive proximal reabsorption, resulting in the presentation of a remarkably constant fraction of the filtered potassium load to the earliest convolutions of the distal tubule. The late portions of this nephron segment in the rat resemble the cortical collecting tubule, both structurally and functionally [3,4]. It is in these tubular divisions that potassium secretion occurs, and the regulation of this process by a variety of luminal and circulatory factors, including hormones, largely determines the final level of urinary excretion of potassium [1, 2, 5]. A variable degree of potassium reabsorption generally occurs along the length of the medullary collecting ducts; this process is not known to be under direct hormonal control