Hené R J, Koomans H A, Rabelink A J, Boer P, Dorhout Mees E J
Department of Nephrology and Hypertension, University Hospital Utrecht, The Netherlands.
Kidney Int. 1988 Nov;34(5):697-703. doi: 10.1038/ki.1988.235.
In six healthy males on a fixed sodium/potassium (Na/K) intake, we studied the relation between plasma K and urine K and Na excretion after an oral K load. Studies were repeated during fludrocortisone (0.5 mg bid) or spironolactone (50 mg qid), that is, after escape from the Na-retaining and Na-excreting effects of these drugs. A steep positive relation between plasma K (ordinate) and urine K or Na (abscissa) was found, compatible with a strong influence of changes in plasma K on K and Na excretion. Fludrocortisone reset the relation to a lower level of plasma K. Spironolactone, on the other hand, had little effect on these relations, although a tendency towards a higher plasma K could be recognized. Paradoxically, the K load was excreted less efficiently during fludrocortisone, probably due to enhanced cellular K deposition. Prolonged kaliuresis relative to the transient rise in plasma K and natriuresis was found only without medication. Only in this situation aldosterone rose and fell parallel to plasma K. We conclude that: 1) chronic mineralocorticoid increase shifts the set point of both K and Na excretion following a K load to a lower plasma K, compatible with resetting of the positive influence of plasma K on distal solute delivery towards a lower plasma K; 2) total kaliuresis is paradoxically low due to enhanced cellular K uptake; 3) blockade of endogenous aldosterone action has relatively little influence on these relations between plasma K and urine K or Na; 4) the contribution of acute aldosterone stimulation to the excretion of a single oral K load can be recognized as a delayed kaliuresis extending beyond the peak in plasma K.
在六名摄入固定钠/钾（Na/K）量的健康男性中，我们研究了口服钾负荷后血浆钾与尿钾及钠排泄之间的关系。在服用氟氢可的松（0.5毫克，每日两次）或螺内酯（50毫克，每日四次）期间重复进行了研究，即，在摆脱这些药物的保钠和排钠作用后。发现血浆钾（纵坐标）与尿钾或钠（横坐标）之间存在陡峭的正相关关系，这与血浆钾变化对钾和钠排泄有强烈影响相一致。氟氢可的松将这种关系重置到较低的血浆钾水平。另一方面，螺内酯对这些关系影响很小，尽管可以识别出血浆钾有升高的趋势。矛盾的是，在服用氟氢可的松期间，钾负荷的排泄效率较低，可能是由于细胞内钾沉积增加。仅在未用药的情况下发现相对于血浆钾和钠排泄的短暂升高有延长的尿钾排泄。只有在这种情况下，醛固酮才与血浆钾平行升高和降低。我们得出以下结论：1）慢性盐皮质激素增加会将钾负荷后钾和钠排泄的设定点转移到较低的血浆钾水平，这与血浆钾对远端溶质输送的正向影响重置为较低的血浆钾水平相一致；2）由于细胞对钾的摄取增加，总的尿钾排泄量反常地低；3）内源性醛固酮作用的阻断对血浆钾与尿钾或钠之间的这些关系影响相对较小；4）急性醛固酮刺激对单次口服钾负荷排泄的贡献可表现为超出血浆钾峰值的延迟性尿钾排泄。
