[Influence of baroreceptors on hypertension, pharmacotherapy with conversion enzyme inhibitors]

Baroreceptor reflex plays an important role in the pathophysiology of essential hypertension. Experiments in dogs could demonstrate that after complete denervation of sinoaortic and cardiopulmonar baroreceptors a long-lasting hypertension with labile blood pressure behavior occurred. The sympathetic tone was enhanced significantly when studied in denervated rats. In patients with essential hypertension no comparable conditions to the "neurogenic hypertension" of animals exist. Therefore, studies in patients after orthotopic heart transplantation are of interest because those patients develop severe hypertension even if cyclosporine is not administered. Preliminary results reported here support a participation of baroreceptors in hypertension of transplanted patients. A further reason of essential hypertension is found on baroreceptor resetting. Changed ion concentrations and/or wall thickness of the respective blood vessels could be the cause. The sympathetic system influences the renin-angiotensin-system and baroreflex activity by central and peripheral mechanisms. It, for example, attenuates Ang-II and the baroreflex via central actions. Converting-enzyme-inhibitors (CEI) act in part as peripheral vasodilators without affecting the heart rate significantly. This effect is possibly due to lacking Ang-II that is able to increase the sensitivity of baroreceptors. In the past it has been shown that the inhibition of tissue-converting enzyme is more responsible for the antihypertensive effects of CEI than that of plasma-converting enzyme. The cardioprotective effects of CEI are suggested to be an important advantage in the treatment of hypertension and heart failure. These cardioprotective actions are partly due to accumulated bradykinin, just as are the hypotensive effects of CEI. The interactions between CEI and the sympathetic system should be differentiated into pre- and postsynaptic actions.(ABSTRACT TRUNCATED AT 250 WORDS)