BARORECEPTOR REGULATION OF VASOPRESSIN AND RENIN SECRETION - LOW-PRESSURE VERSUS HIGH-PRESSURE RECEPTORS

The high-pressure or arterial baroreceptors and low-pressure or atrial receptors are believed to participate in the reflex control of argini ne vasopressin (AVP) and renin secretion. The current concept of the c ontrol system is that at normal blood volume and pressure, afferent im pulses from the receptors tonically inhibit central mechanisms control ling secretion of AVP and renin. Thus, a reduction in blood volume or pressure causes a decrease in receptor activity and a reflex increase in hormone secretion; conversely an increase in blood volume causes th e opposite sequence of events. Furthermore, it is widely believed that cardiac atrial receptors are more important than arterial barorecepto rs in the reflex control of AVP and renin secretion. Evidence presente d in this review challenges the traditional view that cardiac receptor s are importantly involved in the reflex control of AVP secretion. Rec ent evidence indicates that plasma AVP does not increase during progre ssive hypovolemia until volume loss causes a frank fall in arterial pr essure. Furthermore, the evidence suggests that it is the sudden unloa ding of arterial baroreceptors that triggers the surge in AVP secretio n and not signals from cardiac receptors. There is also very little ev idence that increasing the load on cardiac receptors inhibits AVP secr etion. In contrast, there is considerable evidence that renal sympathe tic nerve activity, and hence reflex control of renin secretion, is ti ghtly and inversely coupled to changes in blood volume. Furthermore, t he evidence supports the concept that atrial receptors are the mediato rs of the fine reflex control of renin secretion in response to change s in blood volume. (C) 1994 Academic Press, Inc.