In healthy women we have studied the effects of potassium depletions of different degrees on the generation of some bioregulators of hydro-saline balance. The study has been performed on 20 women in normal potassium balance (N group) and 20 women submitted to potassium depletive treatment by dietary and pharmacological means. On the basis of different patterns of treatment we have obtained three groups i.e. KD1 (n = 8), KD2 (n = 6) and KD3 (n = 6) with potassium cumulative deficit of 160 +/- 43, 198 +/- 22 and 214 +/- 54 mmol, respectively. The renal function was assessed by the clearance method during induced hypotonic polyuria and subsequent moderate antidiuresis induced by low dose infusion of lysine-8-vasopressin. The urinary PGE2, 6-keto-PGF1 (6KPGF) and TxB2 were determined by the RIA method. Moreover, the basal PRA and urinary aldosterone were determined before the renal functional exploration. The data obtained in both KD2 and KD3 groups where renal hypokalemic dysfunctions occurred--indicate that hypokalemia stimulated renin secretion and inhibited the reactivity of renal prostanoid production to the polyuric stimulus. However, in the KD3 group--where the circulating levels of renin, and probably of angiotensin II were the highest--the hypokalemic depression of the synthesis of 6KPGF and TxB2 precursors was attenuated while the synthesis of PGE2 was still inhibited.