The biochemistry of aggression-provoked renin

The biochemistry of the renin-angiotensin system in aggressive mice may question a simple role of the system in blood pressure regulation. When male mice are fighting, their plasma concentration of active renin may rise several hundred fold without affecting blood pressure. The source of this renin is secretion to the blood from the submaxillary gland and the kidneys, but also small salivary glands may contribute. A further source may be salivary renin transferred by bites from one animal to another, as indicated by recent experiments. The renin concentration in saliva of an aggressor during a fight reaches values of 6000 GU/ml (15 mg/ml). The huge increase in plasma renin is caused by fully enzymatic active 40 000 Mw renin. Preliminary data, collected in order to study whether this renin is active also in vivo, show the following: Inactive renin is present in a small invariable concentration. The renin substrate is consumed in vivo and the measured generation rate of angiotensin is that expected from the renin and substrate concentration. The data seem to indicate that the high concentration of aggression-provoked renin is active in vivo. It is unknown how the mouse protects its blood pressure against this hyperactive pressor system.