Effect of tetradecapeptide renin substrate on blood pressure, plasma renin activity, and vasopressin and adrenocorticotropin concentrations.

The effects of third ventricular injection of tetradecapeptide renin substrate (TDP) and natural renin substrate prepared from dog cerebrospinal fluid were compared in anesthetized dogs. Central injection of 350 pmol TDP caused a long lasting increase in arterial blood pressure, a reduction in PRA, and increases in plasma levels of vasopressin, and ACTH. In marked contrast, central administration of equimolar doses of natural renin substrate had no effect on these variables. Intracranial administration of the converting enzyme inhibitor SQ 20881 prevented the effects of central injection of TDP. Thus, TDP exerts its effects via conversion to angiotensin II and does not necessitate the postulation of the action of an enzyme with renin-like activity in the brain.