Mechanism of effect of nicotine on renal water excretion.

CADNAPAPHORNCHAT, PRAVIT, JOHN L. BOYKIN, TOMAS BERL, KEITH M. MCDONALD, AND ROBERT W. SCHRIER. Mechanism of effect of nicotine on renal water excretion. Am. J. Physiol. 227(5) : 1216-1220. 1974.-The mechanism whereby nicotine alters renal water excretion was investigated. In intact anesthetized dogs undergoing a water diuresis, intravenous injection of nicotine increased urinary osmolality (U,,,,) from 104 =t 5 to 345 =t 45 mosmol/kg (P < 0.001) as free water clearance (Cn,o) decreased from 1.5 zt .l to 0.2 & .2 ml/min (P < 0.001). This antidiuresis was reversible and was not associated with reversible alterations in renal hemodynamics or electrolyte excretion. In acutely hypophysectomized, steroid-replaced animals, intravenous nicotine was not associated with an antidiuresis (U,,,, 94 s+ 3 to 96 & 3 mosmol/kg; Cnso , 1.7 & .l to 1.7 =t .l ml/min). The direct intracarotid injection of nicotine also failed to alter renal water excretion (U,,,, 83 rt 5 to 83 + 5 mosmol/kg; &o, 2.0 & .2 to 2.0 & .2 ml/min). In dogs with interrupted cervical parasympathetic pathways, intravenous nicotine produced the same pressor effect as in the intact animals but neither U,,,,, (151 =t 15 to 154 + 16 mosmol/kg) nor CH20 (1.4 + 4 to 1.3 =t 3 ml/min) were altered. In contrast to previous suggestions, these results indicate that the antidiuretic effect of nicotine is not related to a direct intracerebral effect on vasopressin release. Rather, nicotine appears to increase vasopressin release by altering cervical parasympathetic tone.