The response of the juxtaglomerular apparatus to stimuli effecting renin or erythropoietin release in canine renal allografts.

The functioning canine renal allograft produces plasma renin activity (PRA) and erythropoietin (ESF) activity and can maintain normal blood pressure and normal erythropoiesis. Moreover, in response to various provocative stimuli it can: (i) increase plasma renin activity in response to low sodium intake; (ii) suppress PRA in response to high sodium intake; (iii) produce increased serum erythropoietin in response to hypoxia. The granulation activity of the juxtaglomerular apparatus correlates best with the degree of graft rejection and with the PRA in groups manipulated by changing sodium balance. This is not the case with hypoxia. Thus, the juxtaglomerular apparatus, even in the presence of vascular changes seen with the severe degree of rejection in renal allografts, can respond to stimuli that can regulate renin release. Renin production by the transplanted kidney can be dissociated from ESF secretion. Blood pressure changes in the present model were not directly associated with increased PRA or juxtaglomerular apparatus activity. In such conditions hypertension can exist in the presence of suppressed PRA and without hypergranulation of the apparatus. The majority of correlations of this study thus establish a close association of the degree of juxtaglomerular index activity with PRA levels, rather than ESF.