Aggression-provoked huge release of submaxillary mouse renin to saliva

In a normal male mouse, which had been kept isolated for some time, confrontation with another male mouse, resulted in aggressive behaviour, including fighting. The aggressive behaviour resulted in secretion of a few microlitre of saliva with vast renin concentration. The renin concentration in saliva reached values of 6000 Goldblatt units X ml-1, corresponding to 15 mg/ml of renin. This concentration is 6 orders of magnitude higher than normal plasma renin concentrations. The secretory pattern could be mimicked by ip injection of pharmacological doses (2-18 mg/kg) of the alpha-adrenergic agonist phenylephrine. This is probably the first demonstration of a physiological secretion of renin to saliva which may be of importance since renin most likely is injected into the opponent or prey through bites.