Role of bradykinin type 2 receptors in human sweat secretion: translational evidence does not support a functional relationship

Abstract

Bradykinin increases skin blood flow via a cGMP mechanism but its role in sweating in vivo is unclear. There is a current need to translate cell culture and non-human paw pad studies into in vivo human preparations to test for therapeutic viability for disorders affecting sweat glands. Protocol 1: physiological sweating was induced in 10 healthy subjects via perfusing warm (46-48°C) water through a tube-lined suit while bradykinin type 2 receptor (B2R) antagonist (HOE-140; 40 μM) and only the vehicle (lactated Ringers) were perfused intradermally via microdialysis. Heat stress increased sweat rate (HOE-140 = +0.79±0.12 and vehicle = +0.64±0.10 mg/cm2/min), but no differences were noted with B2R antagonism. Protocol 2: pharmacological sweating was induced in 6 healthy subjects via intradermally perfusing pilocarpine (1.67 mg/ml) followed by the same B2R antagonist approach. Pilocarpine increased sweating (HOE-140 = +0.38±0.16 and vehicle = +0.32±0.12 mg/cm2/min); again no differences were observed with B2R antagonism. Lastly, 5 additional subjects were recruited for various control experiments which identified that a functional dose of HOE-140 was utilized and it was not sudorific during normothermic conditions. These data indicate B2R antagonists do not modulate physiologically- or pharmacologically-induced eccrine secretion volumes. Thus, B2R agonist/antagonist development as a potential therapeutic target for hypo- and hyperhidrosis appears unwarranted.