“…Catecholamines, whjch can stimulate renin secretion (Gordon et al, 1967;Tanigawa, Allison & Assaykeen, 1972;Vandongen, Peart & Boyd, 1973), may be increased in the urine and plasma during orthostasis (Gordon et al, 1967;Esler & Nestel, 1973;Molzahn, Dissmann, Halim, Lohmann & Oelkers, 1972), and neural regeneration has been reported to occur as early as the twentyeighth day in human renal transplants (Gazdar & Dammin, 1970). Because the stimulating effect of the sympathetic nervous system and of catecholamines on renin secretion is counteracted by the administration of a beta-receptor blocking agent (Salvetti et al, 1971 ;Tanigawa et al, 1971 ;Meurer, 1971 ;Michelakis & McAllister, 1972;Vandongen et al, 1973;Salvetti et al, 1973;Tobert, Slater, Fogelman, Lightman, Kurtz CSC Payne, 1973), the response of PRA to a beta-receptor blocking agent may be an indirect way of assessing their role in regulating renin secretion.…”