Mechanisms mediating canine renal vasoconstriction induced by nicotine infusion

We investigated the respective contributions of the renin-angiotensin and alpha-adrenergic systems to nicotine-induced, canine, renal vasoconstriction by using saralasin (4 micrograms/kg/min) and phentolamine (25 micrograms/kg/min) blockade respectively. Nicotine infusion (0.024 mg/kg/min) increased mean arterial blood pressure (MABP) (114 +/- 3.0 to 219 +/- 8.0 mmHg) and decreased total renal blood flow (TRBF) (3.12 +/- 0.34 to 1.60 +/- 0.37 ml/min/g). Nicotine infusion produced a significantly lesser blood flow in outer cortex (OC), inner cortex (IC), and outer medulla (OM) compared to control dogs. The intrarenal-artery infusion of saralasin or phentolamine had no effect on the nicotine-induced MABP changes. Phentolamine infusion prior to nicotine resulted in a significantly greater TRBF (P less than 0.01), OC (p less than 0.001), IC (p less than 0.001) and OM (p less than 0.01) flow than in the group that received nicotine only. Saralasin pretreatment prior to nicotine resulted only in a significantly (p less than 0.01) greater OC flow than nicotine only. Our data suggest that while angiotensin II mediates a portion of the action of nicotine on the OC renal vasculature, the alpha adrenergic system predominates as the mediator of nicotine-induced renal vasoconstriction in the first 7 minutes of nicotine infusion.