Changes in active and inactive renin with haemodialysis

Active (A) and inactive (I) plasma renin concentrations (PRC) were examined during haemodialysis in relation to blood pressure and body weight changes. Patients had either one (n = 15) or two (n = 51) remnant kidneys in situ, or were anephric (n = 4). 6 of the two remnant kidney patients had non-functioning renal allografts. Inactive renin was activated by acidification. Renin assay was by enzyme kinetic technique using sheep substrate and angiotensin I radioimmunoassay. Cryoactivation during handling was excluded. For the whole patient group the proportion of IPRC was inversely related to APRC in pre-dialysis plasma (p less than 0.001). APRC and IPRC did not change with heparinisation nor did activation of renin occur across the dialyser. Dialysis with up to 3 kg reduction in body weight did not consistently raise APRC or IPRC. Blood pressure was not significantly correlated with IPRC or APRC during dialysis. In all situations a high APRC was associated with a low IPRC:APRC ratio consistent with preferential secretion of the active form and/or consumption of the inactive renin zymogen.