ANNALS O F CLINICAL A N D LABORATORY SC IE N C E, V ol. 10, N o . 3 C opyright (£) 1980, Institute for C linical Science, Inc.

Patho-Physiology of Kallikrein System

RO BERT W. COLM AN, M.D.

Thrombosis Center and Hematology ¡Oncology, Section o f the Department o f Medicine, Temple University School o f Medicine,

Philadelphia, PA 19140

ABSTRACT

T he properties o f the contact factors, factor XII, high m olecular w eight kininogen and prekallik rein are described as w ell as the abnorm alities in the hereditary deficiencies o f these proteins. The interactions o f each o f these proteins w ith the o ther as w ell as th e ir regulation by plasm a proteolytic in h ib ito rs such as Cl in h ib ito r a n d an tith ro m b in II I are d e lin ea te d . B iochem ical techn iques for m easuring this system are d iscussed. C ond i­tions associated w ith abnorm al synthesis o f these proteins are described . D iseases in w hich increased kinin formation has been docum ented as w ell as disorders w here there is strong ev idence for the activation of kallikrein are presen ted . F u rther know ledge o f this system should increase our u n d er­standing of its pathophysiological alterations.

In troduction

T he plasm a proteolytic enzym e system s of coagulation, fibrinolysis and kinin for­m ation have b een categorized as a “ tan­g led w eb.” T he th ree in terlocking n e t­works are linked together in two ways. F irst, the in itiating pathw ays are com m on and factor XII (Hagem an) factor is a p ro­te in intim ately involved in all. Second, at least four inhibitors w ith defined specific­ity each have the capacity to regulate m ore than one system. T he curren t understand ­ing o f the th ree interlocking netw orks that m ediate the vascular responses necessary for hem ostasis, fibrinolysis and vasodila­tion (kinin form ing system) are d isplayed in figure 1. The working of these enzym es

illustrates the various control m echanism possible in proteolysis, including activa­tion of inactive precursors, positive feed­back, stochiom etric inh ibition , m ultistep am plification and enzym atic degradation o f active products.

Factor XII (a b e ta globulin), m olecular w eight 90,000, is first converted to an ac­tive derivative of the sam e size, factor X lla , u p o n e x p o su re to n e g a tiv e ly charged foreign surfaces w hich in vivo is the subendo thelial basem en t m em brane. T he im portance of factor XII for in itiation o f the various plasm a proteolytic system s is em phasized by the fact that H agem an factor defic ien t plasm a not only has a very p ro lo n g ed partia l th ro m b o p las tin tim e (PTT), w hich m easures the steps to the

2200091-7370/80/0500-0220 $01.20 © Institute for Clinical Science, Inc.

PATHO-PHYSIOLOGY OF KALLIKREIN SYSTEM 2 2 1

form ation o f throm bin, b u t it also fails to support surface in itia ted fibrinolysis as w e ll as th e g en e ra tio n o f b rad y k in in . T hese pathw ays have b een show n to be m ediated by the various H agem an factor substrates.

Activation of P roteins

Activation o f o ther pro teins is req u ired for the coagulation pathw ay to proceed. H agem an factor ac tiva tion o f p rekalli- k re in g en era tes th e enzym e kallik re in w hich digests kininogen to libera te the vasoactive pep tide bradykinin. H ow ever, factor X lla , though a po ten t coagulant, has re la tively less activity in in itiating kalli­kre in or p lasm in formation. To perform these latter functions effectively, factor X lla m ust be p ro teo lysed to H agem an fac­to r fragm ents (XII/). T h e form ation of these activators are a site for control since the even tua l products o f the reaction exert a p o s it iv e fe e d b a c k in th e i r ow n form ation.

Kallikrein can in the fluid phase cleave factor XII to H agem an factor fragm ents (m o lecu la r w e ig h t 30,000) w h ich are m uch more p o ten t in prekallik rein activa­tio n th an th e in ta c t m o le c u le .1 H ig h m olecular w eight (HMW) k in inogen has a central place in th e schem e. It is the p re ­ferred substrate from w hich kallikrein re­leases bradykinin . I t also po ten tiates the conversion of H agem an factor to activated H ag em an factor on a su rfa ce22 an d to H agem an factor fragm ents in th e flu id p h ase .10 In addition, it po ten tiates the ac­tion o f activated H agem an factor on clo t­ting factor XI and H agem an factor frag­m ents on the reciprocal activation of kal­lik re in .14 K allikrein also d irectly activates plasm inbgen to plasm in, the enzym e re ­sponsible for fib rinolysis .4 R ecently, it has b een dem onstrated by us that H agem an factor fragm ents can activate factor V II .21 Thus, a link is created b e tw een the in tr in ­sic and extrinsic pathways. In the d issec­tion of the system , patien ts w ith congeni-

Bradykinn

Plasmin

I Plasminogli

I Prothrombinl— ........s-1------ ^ iSlPL.Ca

FIG U R E 1. Participation of components of the kallikrein-kinin system in coagulation and fibrinoly­sis. Boxed com ponen ts re p re se n t p recu rso rs . Dashed arrows represent transformation of precur­sor to product. Solid arrows are actions of a proteoly­tic enzyme. Dotted arrows are nonproteolytic activa­tion. Kgn = kininogen.

tal ab n o rm a litie s hav e d isc lo se d n ew functions for old proteins.

Throm boplastin Factor

In 1965, F le tch er trait defic iency11 was described as an autosom al recessive d is­order characterized by a d im in ished rate o f surface m ed ia ted coagu lation . T his plasm a possessed an unusual abnorm ality in that the partial th rom boplastin tim e, a m easure of overall intrinsic coagulation, re tu rn ed to norm al as the tim e o f incuba­tion w ith surface (kaolin) was increased. T he factor in norm al plasm a w hich cor­rected the deficiency was partially p u ri­fied. In 1972, the corrective p ro tein was iden tified as p rekallik re in .24 T he F le tch er tra it plasm a also possessed an abnorm ality in the rate o f surface m ediated firinolysis and generated no bradykinin upon incu­bation w ith kaolin. This last abnorm ality is expected if the p lasm a contained no p rekallik re in , b u t one w ould not have re a d ily p re d ic te d an e ffec t u p o n th e coagulation and fibrinolytic pathways.

T he presence of both o f these abnor­m alities suggested an effect upon Hage-

222 COLMAN

man factor, one protein common to each pathway. Correction of both the coagula­tion and fibrinolytic defects of F le tcher trait plasma by activated Hagem an factor in the absence of a surface dem onstrated that the abnormality was a d im in ished rate of formation of activated Hagem an factor. This positive feedback of kallikrein may account for the decrease of surface initiated fibrinolysis and coagulation in F le tcher factor trait.

An additional protein was found to be requ ired for surface activation of H age­man factor as a result o f investigation of three patients in different laboratories. In 1974, a 64-year-old woman Mrs. Williams, was referred, owing to an abnormal intrin­sic coagulation system in which all known factors were normal. The results of further investigation of h er coagulation defect re ­vealed that the abnormal partial th rom ­boplastin time test was corrected by one- q u a r te r v o lu m e o f H a g e m a n t r a i t or F le tcher trait plasma, indicating that these p lasm as c o n ta in e d a d e q u a te c o n c e n ­trations of the missing factor in William’s trait plasma. Unlike F le tcher trait plasma, prolonged incubation with kaolin failed to correct the coagulation abnorm ality of William’s trait.3

A profound defect was also found in the fibrinolytic system of William’s plasma. T h e a d d i t io n o f k ao l in m a rk e d ly in ­creased the fibrinolytic potential o f nor­mal plasma shown as an increase of the reciprocal of the eug lobu lin lysis time ( f igu re 2). As p r e v io u s ly r e p o r te d , F le tcher plasma showed a decreased rate of activation by kaolin. In contrast, Wil­l iam ’s p lasm a show ed virtually no in ­crease of fibrinolytic activity after expo­sure to kaolin. A mixture o f equal volumes of W illiam’s and F le tcher plasma com­plete ly corrected the defect. Similar d e ­fects were found in the conversion of pre- kallikrein to kallikrein.

When kaolin was added to W illiam’s plasma, no bradykinin was detec ted by bioassay. Although this might have been due to the failure of prekallikrein activa-

F ig u r e 2. Comparison of the kaolin-activated euglobulin lysis time of Williams trait plasma, nor­mal plasma, and F letcher trait plasma. Precisely 0.5 ml of each plasma or an equal mixture of Williams and Fletcher trait plasmas were added to 4.25 ml of sodium acetate buffer, pH 4.8. Exactly 0.25 ml of kaolin (8 mg per m l) was then added, the mixture was incubated at 37° C, and aliquots of 0.2 ml w ere re­moved at intervals. The plasmin generated was de­term ined as the euglobulin lysis time.

tion, the addition of H agem an factor frag­ments or even purified plasm a kallikrein did not initiate kinin formation indicating com plete lack of kininogen. This result was confirmed by demonstrating that Wil­liam’s plasma did not react with an an­tiserum against kininogen. However, low molecular w eight kininogen did not cor-

Slice No.

F ig u r e 3. Alkaline disc gel electrophoresis at pH 9.3 of 30 ixg of high molecular w eight kininogen (B4-) obtained from Bio-Gel 0.5 m. A replicate disc gel was sliced and eluted; this eluate was assayed for k in in o g en an tig en by co u n te r im m u n o e lec tro - phoresis and for its ability to correct the coagulation defect of Williams trait plasma.

PATHO-PHYSIOLOGY OF KALLIKREIN SYSTEM 2 2 3

rect the fibrinolytic , coagulation and pre- kallikrein activation defects in W illiam ’s plasm a. A bout 15 p ercen t o f k in inogen is in a h igh m olecular w eight form.

To determ ine w h e th er or not the HMW kininogen is identical to W illiam ’s factor, HM W kininogen was purified w ith th e use o f an im m unoabsorben t colum n of m o n o sp e c if ic k in in o g e n a n tis e ru m . HM W kin inogen ran as a single peak on disc e lec trophoresis. E lu tion of an u n ­sta ined gel show ed th a t the k in inogen an tigen and W illiam ’s factor, as m easured by a coagu lan t assay, w ere in the same p o s it io n (f ig u re 3). T h u s , th e m ajor co ag u lan t facto r m issin g in W illiam ’s p lasm a appears to b e sim ilar or identical to HM W kininogen w hich by itse lf cor­rects all the defects.

Evaluation of A bnorm alities

In evaluating the abnorm alities in defi­c ien t plasm a, it becam e clear th a t prekal- lik rein and HM W kininogen are coagula­tion factors, bo th of w hich are req u ired for H agem an factor activation and function. HM W kininogen has no know n enzym atic activity, b u t it facilitates the generation of a p ro te o ly tic s ite u p o n su rface b o n d H agem an factor. T he H agem an factor ac­tiv ity g en e ra ted is p roportional to th e HM W kininogen input. U pon the surface, HM W kin inogen enhances the function of H agem an factor upon its su b stra tes17— prekallik rein to form kallikrein (brady- k inin re lease) and factor XI to accelerate the PTT. T he effect of kallikrein upon H agem an factor is p resum ed to be a d irect one how ever since HM W kininogen aug­m ents this interaction.

In this system HM W kininogen could accelerate the form ation of activated fac­tor XI and /o r enhance its activity on p re­kallikrein. O ne way to separate these two effects is to use H agem an factor fragm ents already active in the fluid phase. F igure 4 shows the depen d en ce of the initial rate p re k a llik re in ac tiv a tio n on k in in o g en concentration . The potentiation o f Hage-

(units/ml)

FIGURE 4. P re k a ll ik re in (1.0 k a ll ik re in e s te ra s e u n it) w as in c u b a te d w ith H F / (0.6 ¡x g p e r m l) fo r 3 m in a t 3 7 °C in th e p re s e n c e o f v a r io u s c o n c e n ­tra tio n s o f h ig h m o le c u la r w e ig h t k in in o g e n . T h e re su lts a re a m e a n o f tr ip lic a te e x p e r im e n ts .

m an factor fragm ents to convert p rekallik ­re in to kallik rein is a function of the con­ce n tra tio n o f H M W k in in o g e n .14 T h e maxim um effect is seen at abou t 6 p ercen t of the high m olecular w eight k in inogen in norm al p lasm a as determ ined by a clotting assay using W illiam ’s plasm a as a sub­strate. At this concentration m ore than a th ree fold augm entation o f the initial rate is observed.

T he characteristics of a group o f pro­teins w hich are m ainly serine proteases and th e ir cofactors have been d iscussed. It should be no surprise that the m ost effec­tive inh ib ito rs of th ese pathw ays are p ro ­tease inhibitors. Seven naturally occur­ring plasm a inhibitors of proteolytic en ­zym es have b een described. Tw o of these proteins, a 2 m acroglobulin and «! anti­trypsin, make up about 10 percent of totai plasm a proteins by w eight. All o f these proteins are globulins o f w idely varying m olecular w eight. In considering the role

2 2 4 COLMAN

TIM E (min)

F ig u r e 5. Inhibition of kallikrein’s esterolytic activity by antithrombin-heparin cofactor. Kallikrein and antithrombin-heparin cofactor were incubated at 25°C in the presence (A) and absence (0) of hepa­rin. The buffer used for these experiments was 0.15 M sodium chloride in 0.01 M sodium phosphate (pH 7.6). All reactants were extensively diluted in or dialyzed against this buffer. The final concentrations o f enzyme, inhibitor and acidic mucopolysaccharide (if employed) were 250 f i g per ml (2.5 /limol of TAME hydrolyzed m in '1 ml *), 75 fj. g per ml (75 units per ml) and 1 unit per ml, respectively. At appropri­ate times, aliquots were withdrawn and residual kal­likrein activity was determ ined by esterolytic assay as m entioned in Evaluation section. D uring the time course of these experiments, the esterolytic activity of kallikrein rem ained stable when incubated at 25°C w ith buffer. The results presented are repre­sentative of five separate experiments and are ex­pressed as percentages of zero time activity prior to the incubation o f kallikrein w ith antithrom bin- heparin cofactor.

of these inhibitors in the factor XII in ­itia ted pathways, it becom es clear that al­th o u g h th e in h ib ito rs h av e m u ltip le specificities, they have p referen tia l ef­fects. This can be illustra ted by p re sen t­ing the effect of the two major p lasm a in ­hibitors of kallikrein , C l inh ib ito r and anti-throm bin III.

O ne way to approach this problem is to com pare the effect of plasm a congenitally defic ien t in a single inh ib itor w ith the in­hibitory capacity of norm al plasma. A sec­

ond is to study the in teraction o f purified inhibitors w ith the enzym e in question. To dem onstrate the stoichiom etry of the reaction o f kallikrein w ith C l inhibitor, 1600 un its of purified hum an inh ib ito r w ere incubated w ith increasing concen­trations o f kallikrein for 30 m inutes. T he residual kallik rein and C l inh ib ito r w ere th en m easu red .9 T he exact parallelism dem onstrates sto ichiom etric in teraction b e tw een kallikrein and C 1 inhibitor.

U pon in cu b a tio n w ith p lasm a k a lli­k re in , the C l in h ib ito r is d ep le ted (as m easured in a hem olytic assay) and the esterolytic activity o f kallik rein is sup­pressed. S im ilar results w ere shown for kallikrein re lease o f b radyk in in .9 Studies o f the inh ib ition o f purified kallikrein by plasm a from norm al patients and patients w ith h e re d ita ry an g io n e u ro tic ed em a show ed that the ability of plasm a to in ­h ib it kallikrein paralle led the C l inh ib itor co n cen tra tio n s an d was m ark ed ly d e ­creased in hereditary angioedem a.

T he effect of another m ajor inhibitor anti-throm bin II I w ith kallikrein has been exam ined by u s .12 It is dem onstrated in figure 5 tha t purified anti-throm bin III in- a c tiv a te s th e e s te ro ly t ic a c tiv ity o f purified kallikrein. T he process w ith in­h ib ito r in excess obeys pseudo first order kinetics. H eparin (low er curve) appears to accelerate the rate of inactivation. Sim ilar results are ob ta ined w h en the ability of kallikrein to re lease bradykinin m easured in a radioim m unoassay is m easured ind i­cating that the anti-throm bin III affects th e p ro teo ly tic activity o f kallik re in as w ell as its esterolytic activity.

Once again, the accelerating effect of heparin was seen. In norm al plasm a, an ti­throm bin III apparently plays little role in inh ib iting kallikrein. Thus, the degree of inh ib itio n by norm al plasm a is not altered by addition o f as m uch as 50 units p er ml heparin. In contrast, p lasm a from patients w ith hereditary angioedem a had little in­hibitory capacity m easured by esterase or b radykinin release. T his inhibitory capac­ity is m a rk e d ly in c re a s e d by ad d in g

PATHO-PHYSIOLOGY OF KALLIKREIN SYSTEM 2 2 5

Deficiency of Proteins Necessary for Kinin Formation

I. HereditaryA. Factor XII deficiency (Hageman trait)B. Prekallikrein deficiency (Fletcher trait)C. High molecular weight kininogen deficiency

(Williams, Fitzgerald and Flaujeac traits)

II. AcquiredA. Dengue hemorrhagic feverB. Cirrhosis of the liver

TABLE I

th e ra p e u tic co n cen tra tio n s o f h ep a rin . T hese observations suggest a poten tial role for hep arin in trea ting the acute m ani­festations o f the disease.

W ith this background, the role of the k a llik re in system can b e su rv ey ed in hum an disease. In tab le I are sum m arized conditions w hich are associated w ith ab­norm al synthesis o f one or more of the p ro te in s in v o lv ed in th is system . T he th ree h ered ita ry syndrom es have b een p reviously discussed. In dengue hem or­rhagic fever, a se lec tiv e d efic ien cy o f p la sm a p re k a ll ik re in occu rs p ro b ab ly ow ing to th e ab n o rm al liv e r fu n c tio n s tu d ies .8 In cirrhosis o f the liver, the m ean p re k a ll ik re in lev e ls are d e p re s s e d to about 25 p ercen t o f norm al and in the sev­eral cases, concentrations ofOto 10 percen t are usual.2,23 In contrast, factor XII is d e­creased to abou t 40 percen t of norm al, and HM W kin inogen is reported reduced to a sim ilar level.

O f greater in te re st are the conditions in w hich increased k inin formation has b een docum ented (table II). In carcinoid syn­d ro m e6,7 and postgastrectom y dum ping syndrom e ,18 the vasom otor sym ptom s are

TABLE II

Disorders Leading to Increased Kinin Formation

I. HereditaryA. Hereditary angioedema

II. Acquired (documented)A. Carcinoid syndromeB. Postgastrectomy dumping syndromeC. Septic stockD. Hemorrhagic pancreatitis

TABLE III

Disorders Leading to Kallikrein Activation

I. Acquired (suspected)A. Coronary artery diseaseB. Intravascular coagulationC. HyperlipoproteinemiaD. Transfusion reactionsE. Typhoid feverF. Nephrotic syndrome

Kinin formation not documented.

re la ted to bradykinin release by e ith e r tis ­sue or plasm a kallikrein. Septic shock is accom panied in m an by decreased prekal­lik rein and kallikrein inh ib itory acitivty, form ation of active kallik re in16 and e le ­vated k in in leve ls .19 The latter m ay con­tribu te to the early phases o f reversib le hypotension. E leva ted bradyk in in levels in pancreatitis are probably due to re lease o f trypsin and pancreatic kallikrein.

In tab le II I are listed disorders in w hich there is a strong ev idence for activation of kallikrein, including decreased factor XII and p rekallik rein d im in ished kallikrein inhibitory activity and form ation o f kalli- k re in -C l inh ib ito r com plexes. In coronary artery d isease ,20 m yocardial iscehm ia is accom panied by these changes in over h a lf the cases. D issem ination intravascu- lar coagulation (DIC) is accom panied by ev idence for kallikrein activation w hen endo thelia l injury is involved, such as in s e p s is , b u t n o t in D IC o w in g to n eo p lasin .15 At the tim e w hen positive b lood cultures and pyrexia are found in typhoid fever, the kallikrein system is ac­tivated w ith the changes d isap p ea rin g during convalescence .5 In the nephro tic syndrom e, activation of H agem an factor

TABLE IV

Disorders in Which Kallikrein-Kallikrein Abnormalities Have Been Suggested

I . AcquiredA. Thermal injuryB. ArthritisC. Allergic disordersD. Cystic fibrosisE. Migraine syndrome

226 COLMAN

levels lead to k a llik re in factor XI and plasm inogen activation .13

Finally, kallikrein activation has b een suggested to occur in various conditions b u t none o f these have b een show n defi­n itely (table IV). F u rth e r investigation is im portant to appreciate the role o f this d e fe n s iv e sy s tem in in flam m ato ry disorders.

References1. Ba g d a s a r ia n , A ., La h ir i , B., a n d C o l m a n , B.

W .: O rig in o f h ig h m o le c u la r w e ig h t a c tiv a to r o f p re k a ll ik re in . J. B iol. C h e m . 248:7 7 4 2 -7 7 4 7 , 1973.

2. Ba g d a s a r ia n , A ., L a h ir i , B., T a l a m o , B. C ., W o n g , P., and C o l m a n , B. W .: Immunochem i­cal studies of plasma kallikrein. J. Clin. Invest. 54:1 4 4 4 -1 4 5 4 , 1974.

3. C o l m a n , R. W., Ba g d a s a r ia n , A., T a l a m o , R.C., Sc o t t , C. F„ Se a v e y , M„ Gu im a r a e s , J. A., Pie r c e , J. V., and Ka p l a n , A. P.: Williams trait: Human kininogen deficiency w ith dim inished levels of plasminogen proactivator and prekal­likrein associated w ith abnorm alities o f the Hageman factor dependent pathways. J. Clin. Invest. 5 6 :1 6 5 0 -1 6 6 2 , 1975.

4. C o l m a n , R. W., Br a u n , W. E., B u s c h , G. J., D a m m in , D ., and M e r r il , J. P.: Coagulation studies in the hyperacute and other forms of renal allograft rejection. New Engl. J. Med 281 :6 8 5 -6 9 1 , 1969.

5. C o l m a n , R. W ., E d e l m a n , R., Sc o t t , C . F ., a n d GlLMAN, R. H.: P la sm a k a llik re in ac tiv a tio n a n d in h ib it io n d u r in g ty p h o id fev er. J. C lin . In v e s t. 61:2 8 7 -2 9 6 , 1978.

6. C o l m a n , R. W., Ma s o n , J. W., and Sh e r r y , S.: Studies on the kallikreinogen kallikrein en­zyme system of human plasma. Assays of com­ponents and prelim inary observations in dis­ease states. Ann. Int. Med. 71 :7 6 3 -7 7 3 , 1969.

7. C o l m a n , R. W., W o n g , P. Y., and Ta l a m o , R.C . K allikrein-kinin system in carcinoid and postgastrectomy dumping syndromes. Proceed­ings of the Conference on the Chemistry and Biology o f th e K allikrein-K m in System in H ealth and Disease. Pisano, J. J. and Austen, K.F., eds. Washington, U.S. Government Print­ing, 1977, pp. 4 8 7 -4 9 4 .

8. E d e l m a n , R ., N im m a n n it y a , S., C o l m a n , R. W ., T a l a m o , a n d T o p , F . H .: E v a lu a tio n o f th e p la sm a k in in sy s tem in d e n g u e h e m o rrh a g ic fever. J. L ab . C lin . M e d . 8 6 :4 1 0 -4 2 1 , 1975.

9. G ig l i, I., M a s o n , J. W., C o l m a n , R. W., and A u s t e n , K. F.: Interaction of plasma kallikrein with the C l inhibitor. J. Immunol. 104:5 7 4 - 581, 1970.

10. G r if f in , J . M . a n d C o c h r a n e , C . G .: M e c h a ­n ism s for in v o lv e m e n t o f h ig h m o le c u la r w e ig h t k in in o g e n in su rface d e p e n d e n t re a c tio n s o f

Hageman factor. Proc. Nat. Acad. Sei 73:2554- 2558, 1970.

11. H a t h a w a y , W . E., B e l h a n s o n , L . P., and H a t h a w a y , M. S.: Evidence for a new throm­b o p las tin factor; C ase report, coagula tion studies, and physiochem ical studies. Blood 26:521-532, 1965.

12. L a h ir i , B ., Ba g d a s a r ia n , A., M it c h e l l , B., T a l a m o , R. C ., C o l m a n , R. W ., and R o s e n ­b e r g , R. D.: Antithrombin-heparin cofactor: An inhibitor of plasma kallikrein. Arch. Biochem. Biophys. 175:737-747, 1976.

13. L a n g e , L . G ., C a r v a l h o , A. C ., Ba g d a s a r ia n A., L a h ir i , B., and C o l m a n , R. W .: Activation of Hageman factor in the nephrotic syndrome. Amer. J. Med. 56:565-569, 1974.

14. L iu , C . Y., Sc o t t , C. F., Ba g d a s a r ia n , A., P i e r c e , J. V., Ka p l a n , A. P ., a n d C o l m a n , R. W .: P o te n tia t io n o f fu n c tio n o f H a g e m a n fac to r f ra g m e n ts b y h ig h m o le c u la r w e ig h t k in in o g e n . J. C lin . In v e s t. 60:7-17, 1977.

15. M a s o n , J. W. and C o l m a n , R. W.: The role of Hageman factor in dissemination intravascular coagulation induced by septicemia, neoplasia or liver disease. Thromb. Diath. Haemorrh. 26:325-331, 1971.

16. M a s o n , J . W ., Kl e e b e r g , U. R., D o l a n , P., and C o l m a n , R. W .: Plasma kallikrein and Hage­man factor in gram negative bacteremia. Ann. Int. Med. 73:545-551, 1970.

17. M e i e r , H. L ., S c o t t , C . F., M a n d l e , R., J r ., W e b s t e r , M ., P ie r c e , J . V., C o l m a n , R. W ., and Ka p l a n , A. P.: R equirem ents for the con­tact activation of human Hageman factor. Ann. N. Y. Acad. Sei. 283:93-103, 1977.

18. M in n a , J. D., R o b b o y , S. J ., and C o l m a n , R. W .: D issem inated Intravascular Coagulation in Man. Springfield, C. C Thomas, 1974.

19. O ’D o n n e l l , T . F., J r ., C l o w e s , G . H . A., J r ., Ka p l a n , A. P ., a n d C o l m a n , R. W .: K in in a c ti­v a tio n in th e b lo o d o f p a tie n ts w ith se p tic m an . Surg. G y n . O b s t. 143:539-544, 1976.

20. P i t t , B., M a s o n , J ., C o n t i , C . R., and C o l m a n , R. W .: Observations on the plasma kallikrein system during m yocardial ischem ia. Trans. Amer. Assoc. Physicians 82:98-108, 1969.

21. Ra d c l i f f e , R., B a g d a sa r ia n , A., C o l m a n , R. W., and NEMEBSON, Y.: Activation of factor VII by Hageman factor fragments. Blood 50:611- 618, 1977.

22. W e b s t e r , M . E., G u im a r a e s , J . A., Ka p l a n , A. P ., C o l m a n , R. W ., a n d P ie r c e , J. V.: A ctiv a tio n o f su rfa c e -b o n d H a g e m a n facto r: P re e m in e n t ro le o f h ig h m o le c u la r w e ig h t k in in o g e n a n d e v i d e n c e fo r a n e w f a c to r . K in in s : P h a r ­m a c o d y n a m ic s a n d B io lo g ica l R o les . S ic u te r i,F., B ack, N ., a n d H a b e r la n d , G . L ., ed s . N ew York, P le n u m P re ss , 1976, p p . 285-299.

23. W o n g , P . Y., C o l m a n , R. W ., T a l a m o , R. C., and Ba b io r , B. M.: The kallikrein bradykinin system in chronic alcoholic liver disease. Ann. Int. Med. 77:205-209, 1972.

24. W u e p p e r , R. D.: Prekallikrein deficiency in man. J. Exp. Med. 138:1345-1355, 1973.