Kallikrein-kinin system and adenosine metabolism system of blood and heart and their changes at hypothalamic-hypophyseal stimulation in rabbits of different age.

It was shown that kallikreinogen content was decreased in blood of old rabbits, kallikrein activity was somewhat increased, kininase activity was significantly decreased. In old animals, adenosine metabolism was activated, this being evident from the rise of 5'-nucleotidase and adenosine deaminase activity in blood and myocardium. Hypothalamic stimulation resulted in significant activation of the kallikrein-kinin system and sharp increase of kallikrein activity, the shifts being less marked in old animals than in adults. In adult animals, vasopressin administration elicited more marked activation of the kallikrein-kinin and adenosine metabolism systems.