Role of cardiopulmonary mechanoreceptors in the postural regulation of renin.

To change the stretch on cardiopulmonary mechanoreceptors, large shifts of blood in the capacity space were elicited by tilting and by exerting positive lower body pressure in the tilted position. Twelve volunteers underwent invasive hemodynamic studies and in 10 other subjects cardiac size was determined by radionuclide cardiography. In all 22 subjects tilting caused the expected increase of renin, which was abolished by lower body compression. Decompression caused renin to increase again. Right atrial pressure in invasive studies and end-systolic and end-diastolic counts in noninvasive studies showed a significant and strong negative correlation with renin and norepinephrine levels. Thus, the degree of stretch of the cardiopulmonary mechanoreceptors is a major determinant of reflex regulation of renin release in humans.