1313
against a role of prostaglandins in the pathogenesis of Shy-Drager syndrome. also argues
Hypertension-Endocrine Branch, National Heart, Lung, and Blood Institute, National Institute of Health, Bethesda, Maryland 20014, U.S.A.
REQUIREMENT
OF FACTOR XII FOR CRYOACTIVATION OF INACTIVE RENIN IN HUMAN PLASMA
HANS-GEORG GULLNER
FACTOR XII IN ENDOGENOUS ACTIVATION OF INACTIVE RENIN
SIR,-We are pleased that Dr Atlas and colleagues (March 11, p. 555) concur with our evidence (Jan. 14, p. 102) that
cryoactivation of inactive plasma renin is inhibited by the protease inhibitor diisopropylfluorophosphonate (D.F.P.), which suggests that the process is protease dependent. How closely we agree is difficult to determine from their brief abstract,’ published after we wrote you. With such apparent concurrence on the data, there need be few disagreements about the conclusions. Each of the three main methods used for activating inactive renin tends to rule out a distinctive feature of the other two as an essential ingredient for activation. Thus, trypsin-induced activation proves that neither cold temperature nor low pH are essential. Cold temperature (with unlowered pH) proves that neither exogenous protease nor low pH are necessary. Finally, low pH proves that neither cold temperature nor exogenous protease are required. This process of elimination suggests that an activating mechanism common, or incidental, to all three procedures may be involved. We are therefore not surprised that Atlas et al. find evidence that an acid-protease mediates acid-activation of inactive renin in plasma. Indeed Morris and Lumbers2 proposed such enzymic mediation, probably by pepsin (derived from acid-activated pepsinogen), in their studies of inactive renin in amniotic fluid. Our contribution was to demonstrate an endogenous plasma protease operative at normal, even slightly alkaline, pH, which almost certainly excludes the action of pepsin. It was not unreasonable to suggest that our data brought us closer to the in-vivo activator of inactive renin. We reject the argument that physiological significance of such a protease must be excluded simply because plasma is rich in protease inhibitors. Such reasoning would, among other’things, preclude operation of the blood coagulation system in the body. Which brings us to another observation about cryoactivation, apparently connecting the renin and blood coagulation systems for the first time. The techniques we used for cryoactivation and determination of angiotensin were the same as before, except that sodium citrate was the anticoagulant. The human plasmas were normal controls (Col 1-60 from Dade, Miami, Florida, and 4B196 from General Diagnostics [Warner-Lambert] Morris Plains, New Jersey). Factor-xn-dencient plasmas were from Dade (CF 12-18) and General Diagnostics (OA270, 389G370), each more than 99% deficient. After reconstitution, these normal and deficient plasmas were either kept frozen at -20°C or held at -4°C for 3 days, then plasmarenin-activity (P.R.A. at 370C determined by radioimmunoassay. The data from six determinations of the Dade plasmas, and four determinations of the General Diagnostics plasmas were aver-
aged (see table). The basal, frozen control P.R.A. values were very similar in normal and factor-xn-deficient plasmas. Factor-xn deficiency did not lower the basic angiotensin-generation rate in plasma. In contrast, it lowered the level of attainable activation by approximately 50% in the deficient plasmas from both sources (P
against a role of prostaglandins in the pathogenesis of Shy-Drager syndrome. also argues
Hypertension-Endocrine Branch, National Heart, Lung, and Blood Institute, National Institute of Health, Bethesda, Maryland 20014, U.S.A.
REQUIREMENT
OF FACTOR XII FOR CRYOACTIVATION OF INACTIVE RENIN IN HUMAN PLASMA
HANS-GEORG GULLNER
FACTOR XII IN ENDOGENOUS ACTIVATION OF INACTIVE RENIN
SIR,-We are pleased that Dr Atlas and colleagues (March 11, p. 555) concur with our evidence (Jan. 14, p. 102) that
cryoactivation of inactive plasma renin is inhibited by the protease inhibitor diisopropylfluorophosphonate (D.F.P.), which suggests that the process is protease dependent. How closely we agree is difficult to determine from their brief abstract,’ published after we wrote you. With such apparent concurrence on the data, there need be few disagreements about the conclusions. Each of the three main methods used for activating inactive renin tends to rule out a distinctive feature of the other two as an essential ingredient for activation. Thus, trypsin-induced activation proves that neither cold temperature nor low pH are essential. Cold temperature (with unlowered pH) proves that neither exogenous protease nor low pH are necessary. Finally, low pH proves that neither cold temperature nor exogenous protease are required. This process of elimination suggests that an activating mechanism common, or incidental, to all three procedures may be involved. We are therefore not surprised that Atlas et al. find evidence that an acid-protease mediates acid-activation of inactive renin in plasma. Indeed Morris and Lumbers2 proposed such enzymic mediation, probably by pepsin (derived from acid-activated pepsinogen), in their studies of inactive renin in amniotic fluid. Our contribution was to demonstrate an endogenous plasma protease operative at normal, even slightly alkaline, pH, which almost certainly excludes the action of pepsin. It was not unreasonable to suggest that our data brought us closer to the in-vivo activator of inactive renin. We reject the argument that physiological significance of such a protease must be excluded simply because plasma is rich in protease inhibitors. Such reasoning would, among other’things, preclude operation of the blood coagulation system in the body. Which brings us to another observation about cryoactivation, apparently connecting the renin and blood coagulation systems for the first time. The techniques we used for cryoactivation and determination of angiotensin were the same as before, except that sodium citrate was the anticoagulant. The human plasmas were normal controls (Col 1-60 from Dade, Miami, Florida, and 4B196 from General Diagnostics [Warner-Lambert] Morris Plains, New Jersey). Factor-xn-dencient plasmas were from Dade (CF 12-18) and General Diagnostics (OA270, 389G370), each more than 99% deficient. After reconstitution, these normal and deficient plasmas were either kept frozen at -20°C or held at -4°C for 3 days, then plasmarenin-activity (P.R.A. at 370C determined by radioimmunoassay. The data from six determinations of the Dade plasmas, and four determinations of the General Diagnostics plasmas were aver-
aged (see table). The basal, frozen control P.R.A. values were very similar in normal and factor-xn-deficient plasmas. Factor-xn deficiency did not lower the basic angiotensin-generation rate in plasma. In contrast, it lowered the level of attainable activation by approximately 50% in the deficient plasmas from both sources (P
