Increased plasma prorenin but not renin after bilateral ureteral ligation in dogs

Plasma prorenin is normally higher than renin and usually changes in response to the same stimuli. In dogs, plasma prorenin and renin disappear after bilateral nephrectomy, indicating that both are of renal origin. It has been proposed that prorenin may mediate tissue renin systems via its reversible intrinsic renin-like activity. The renin-angiotensin system has been implicated in the changes in renal function that occur with bilateral ureteral obstruction, but plasma prorenin has not been investigated. We therefore studied the effect of 48-hour bilateral obstruction on plasma prorenin in two groups of dogs: one was volume expanded (N = 5), while the other group (N = 6) was euvolemic. Plasma prorenin concentration increased fourfold in both groups, angiotensinogen increased twofold, while plasma renin activity was unchanged. Following release of obstruction, plasma renin fell slightly while prorenin and angiotensinogen remained elevated. There was a positive relationship between plasma prorenin and renin before (r = 0.63, P less than 0.05) and after (r = 0.76, P less than 0.01) obstruction. Post-obstruction, ERPF and GFR were subnormal but filtration fraction was maintained; the higher the ERPF and GFR the higher the plasma prorenin post-obstruction (r = 0.83, P less than 0.01 and r = 0.77, P less respectively; N = 11). These results show that impairment of renal function during bilateral obstruction is associated with an increase in plasma prorenin but not renin. Nonetheless, there is a positive relationship between plasma prorenin and renin both pre- and post-obstruction. Thus, preferential impairment of clearance of prorenin relative to renin may occur during bilateral obstruction.(ABSTRACT TRUNCATED AT 250 WORDS)