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1 upportng nformton for Towrds more useful n vtro toxcty dt wth mesured concentrtons by M.B. Herng R.H.M.M. chreurs F. Busser.T. vn der g B. vn der Burg nd J..M. Hermens Contnng 0 pges 2 tbles nd 2 fgures.

2 upplementry nformton on the dscusson of the reltve potences. Tble 3 n the mnuscrpt shows tht the rp nomnl of octylphenol slghtly decreses wth ncresng serum percentge (down to fctor 2 lower). We doubted whether ths ws rel trend or ust concdentl mesurement vrblty. Therefore we modelled the dependency of the nomnl reltve potency on serum content wth respect to bndng to lbumn nd HBG. The relton between rp nomnl nd rp of octylphenol cn be descrbed s n equton : rp ff rpnomn l () ffo In ths equton the frctons re those t the C 50nomnl of the compound n queston nd the nd O n the subscrpts denote estrdol nd octylphenol respectvely. The frcton of lgnd (ff ) cn be derved from equton 2 (see lso ppendx I). ff totl ff totl ff (2) In ths equton ff nd ff re the unoccuped ( ) frcton of lbumn nd HBG. Combnton of equtons nd 2 yelds equton 3. rp no mn l rp O totl totl ff ff O O totl totl ff ff O (3) In ths equton ff nd ff re the unoccuped frctons of lbumn nd HBG respectvely when there s only estrdol present nd ff O nd ff O re those when there s only octylphenol present. Bsed on equton 3 model ws wrtten nd run wth Berkeley Mdonn of whch the scrpt cn be found n ppendx III. rmeter vlues from tble n the rtcle were used s well s vlues for some ddtonl prmeters lsted n tble. Fgure shows how the nomnl reltve potency of octylphenol decreses wth ncresng serum content wth only mnor decrese n the rnge of 5-50% serum s ws used n our experments. To verfy f other compounds wth usully lower ffnty for lbumn mght show more pronounced effect of serum the ffnty constnt of octylphenol ws replced by those of dethylstlbestrol (D) nd pp -DDT (see tble ). Note tht for these two compounds the ntrnsc estrogenc potency of octylphenol ws tken; therefore the bsolute vlue of the nomnl reltve potences clculted for these compounds s unrelble. The trend n nomnl reltve potency however s relstc becuse tht s determned by the compound-specfc proten bndng.

3 Nomnl reltve potency % 0.00% 0.00% 0.0%.0% 0% 00% erum % Fgure. Modelled effect of serum % on nomnl reltve estrogenc potency of octylphenol (thnnest lne) D (mddle lne) nd pp -DDT (thckest lne) bsed on n ntrnsc reltve potency of 0-3 (note tht ths s not the rel reltve potency of D nd pp -DDT). Tble. xtr prmeter vlues for nomnl reltve potency model (equton 3). rmeter Vlue ource rp ff ff ff O tble 3 rtcle clculted * clculted * clculted * ff O 0.98 clculted * (D) M - 2 (pp -DDT) M - 3 * these vlues were clculted wth the bndng model from equton 2 n the rtcle Tble 2 gves the outcome of the model for the nomnl reltve potences t the three serum percentges tested for the three compounds modelled. The clculted vlues for octylphenol correspond well wth the mesured ones (Tble 3 n rtcle) consderng the clculton model s smplfcton wth severl ssumptons. The trend of decresng rp nomnl wth ncresng serum percentge n prtculr s very smlr. Ths shows tht the mesured decrese n rp nomnl ws not concdentl mesurement vrblty but rel trend. 2

4 Tble 2. Clculted nomnl reltve estrogenc potences (rp) of octylphenol D nd pp -DDT t dfferent serum contents. rp nomnl octylphenol rp nomnl D rp nomnl pp -DDT 5% serum 20% serum 50% serum D ctully shows smller decrese n rp nomnl (0%) thn octylphenol (23%) whle pp -DDT does not show ny decrese wth ncresng serum content. pprently compounds wth lower ffnty for lbumn show lower effect of serum. Ths s n contrst to the expectton tht the lter strt of the decrese curve of these compounds would show hgher effect of serum n the rnge of -50% serum f the curve would run prllel to tht of octylphenol. Clerly however the curves of D nd pp -DDT do not run prllel to the curve of octylphenol: they re quenched. s the ffnty of octylphenol for lbumn s hgh for such n unspecfc bndng proten most other compounds wll hve lower ffnty. Therefore we do not expect lrge effects of serum content on nomnl reltve potences of the morty of compounds. Only when there s no serum present t ll n the ssy lke n the yest estrogen screen (Y) 4 very dfferent rp nomnl cn be found for compounds wth hgh lbumn ffnty (fgure : rp nomnl s for octylphenol t 0% serum). Gülden nd co-workers 5 found much lrger effects of vlblty on the nomnl reltve potences (decrese down to 6% nd ncrese up to 3%) but ths ws n effect due to lrger cell number n the suspenson not serum content. Hydrophobcty nd cell membrne content cn therefore probbly ply lrger role n the system-dependency of the rp nomnl thn lbumn ffnty nd serum content do. However ths effect wll not come to expresson n ll n vtro ssys s for exmple n the reporter gene ssy used here the cell content wll not only determne the mount of vlblty loss but sometmes lso the heght of the response. These two effects cn nullfy ech other. The reltve potences n Tble 3 n the rtcle re more or less constnt (no trend) whch s s expected but re tmes hgher thn the nomnl reltve potences. The generl nfluence of the lbumn bndng ffnty of test compound on the dfference between rp nomnl nd rp ws studed n more detl usng smple exposure model. Ths model ws bsed on equtons nd 2 nd the exct scrpt cn be found n ppendx IV. Model clcultons were performed for the condtons of our ssy wth 5% serum nd estrdol s the reference compound. The result of ths smulton s shown n fgure 2. If reltve potences would be the sme s the nomnl reltve potences ll brs of the sme seres would hve the sme heght nd ll lnes would be completely horzontl. Ths s clerly not the cse for compounds wth bndng ffnty hgher thn 0 5 M 3

5 nd nomnl reltve potency hgher thn 0-6 : for these theoretcl compounds the reltve potency ncreses consderbly becomng more thn 0-fold hgher thn the nomnl reltve potences. Compounds wth low nomnl reltve potences do not show ny effect of -vlue here becuse these compounds hve such hgh C 50 -vlue tht the lbumn must be sturted wth lgnd t ths concentrton regrdless of the ffnty of the lgnd for lbumn. Compounds wth low -vlues do not show n effect of bndng on the dfference between nd nomnl reltve potences becuse they do not bnd to sgnfcnt extent. For prortston purposes chemcls re usully rnked bsed on ther nomnl reltve potency. Fgure 2 shows tht the rnkng cn chnge f concentrtons re used to estmte reltve potences. Ths concluson s only bsed on the effect of bndng to lbumn whle bndng to other protens (e.g. HBG) nd other processes my lso led to chnge n rnkng when bsed on reltve potences Free reltve potency log Fgure 2. ffect of the ffnty constnt ( ) of compound for lbumn on the dfference between the nomnl reltve potency nd the reltve potency n n ssy wth 5% serum present n the culture medum. nes connect brs of the sme nomnl reltve potency: 0-6 (blck) 0-4 (drk grey) 0-2 (strped) nd (lght grey). References () Rowlnd M.; Tozer T. N. Clncl phrmcoknetcs; 3 ed.; Wllms & Wlkns: Med hldelph 995. (2) heehn D. M.; Young M. ndocrnology (3) tyl..; Nth. Indn J. xp. Bol (4) rnold. F.; Robnson M..; Notdes. C.; Gullette. J. Jr.; Mcchln J.. nvron. Helth erspect (5) Gülden M.; Mörchel.; ebert H. Toxcol. In Vtro

6 ppendx I. Model dervtons ssumng sngle bndng ste per proten the bndng recton of lgnd () to proten () cn be formulted s (I.) where s the concentrton of lgnd s the concentrton of unoccuped proten nd s the concentrton of lgnd-proten complexes. The w of Mss cton sttes tht t bndng equlbrum the ffnty constnt ( ) cn be expressed s n equton I.2 2. (I.2) The mss blnces of system contnng one proten nd one lgnd re totl totl (I.3) n whch totl nd totl re the totl concentrtons of proten nd lgnd respectvely. The nd bound concentrtons n equton I.2 cn be substtuted wth the followng defntons: ff ff totl ( ff ) (I.4) totl totl n whch ff nd ff re the frctons of lgnd nd proten respectvely. Rerrngement of the resultng equton leds to equton I.5 2 : ff ff totl (I.5) lterntvely f the proten mss blnce s used to substtute n equton I.2 nd the resultng equton s rerrnged equton I.6 cn be obtned whch corresponds wth the ngmur equton: totl (I.6) Ths equton cn be used to substtute n the mss blnce equtons to obtn equton I.7: 5

7 6 totl totl totl totl (I.7) s clculted frst by the modellng softwre usng the lower formul of equton I.7 (for exmple by the GU ROOT functon n Berkeley Mdonn). Wth the obtned the upper formul of equton I.7 cn be used to clculte or ny other desred prmeter. In generl f there re n dfferent lgnds n whch bnd wth bndng ssocton constnt to m dfferent protens m the mss blnces become: totl totl totl totl (I.8) For exmple wth one lgnd nd two protens (lbumn) nd (HBG) the mss blnces re: totl totl totl totl totl totl totl (I.9) nd for two lgnds (estrdol) nd (xeno-estrogen) nd two protens nd they become:

8 7 totl totl totl totl totl totl totl totl totl totl (I.0) References () Rng H..; Rtter J.M.; Dle M.M. hrmcology; Churchll vngstone: New York 998. (2) Rowlnd M.; Tozer T.N. Clncl hrmcoknetcs; Wllms & Wlkns: Med (hldelph) 995.

9 ppendx II. Bndng model scrpt ;Model for bndng of one compound to two serum protens (lbumn nd HBG) MTHOD R4 RNM TIMlogtot RNM TRTTIMlogtot0 RNM TOTIMlogtotf RNM DTMINdmn RNM DTMdmx RNM DTOUTdout ; s log totl concentrton of lgnd logtot0-0.0 logtotf0.0 dmn.e-6 dmx. dout e4 3.7e8 t.3e-4 t0.5e-7 ; s ffnty constnt of lgnd for lbumn defult s for estrdol ; s ffnty constnt of lgnd for HBG defult s for estrdol ; s totl lbumn concentrton defult s for 00% FC ; s totl HBG concentrton defult s for 00% FC fff/tot fff/t ffsf/t fb(tot-f)/tot ; s frcton of lgnd ; s unoccuped frcton of lbumn ; s unoccuped frcton of HBG ; s bound frcton of lgnd tot0.00**logtot f(.0-(*f)/(.0*f))*t f(.0-(*f)/(.0*f))*t ; s conc. of unoccuped lbumn ; s conc. of unoccuped HBG GU ftot/2. ROOT f(.0*t/(.0*f)*t/(.0*f))*f-tot ;s conc. of lgnd IMIT f > 0. IMIT f < tot 8

10 ppendx III. Nomnl reltve potency model scrpt ;Model to study the course of the nomnl reltve potency s functon of proten content nd ;proten sturton MTHOD R4 RNM TIMlogfserum ; s log of frcton of serum present n medum RNM TRTTIMlogfserum0 RNM TOTIMlogfserumf RNM DTMINdmn RNM DTMdmx RNM DTOUTdout RNM DTd logfserum0-6 logfserumf 0 dmn.e-6 dmx dout.e-2 dt e4 3.7e8 O.0e7 O 4.7e5 Rf e-3 ff ff ffo 0.87 ffo 0.98 fserum0**logfserum t 3.7e-4*fserum t 5e-8*fserum ; s ffnty constnt of estrdol for lbumn ; s ffnty constnt of estrdol for HBG ; s ffnty constnt of octylphenol for lbumn ; s ffnty constnt of octylphenol for HBG ; s reltve potency of octylphenol ; s unoccuped frcton of lbumn t nomnl C50 of estrdol ; s unoccuped frcton of HBG t nomnl C50 of estrdol ; s unocc. frcton of lbumn t nomnl C50 of octylphenol ; unoccuped frcton of HBG t nomnl C50 of octylphenol ; s totl conc. of lbumn ; s totl conc. of HBG ffo /( O*t*ffO O*t*ffO) ; s frcton octylphenol ff /( *t*ffo O*t*ffO) ; s frcton estrdol Rt Rf*(ffO/ff) ; s nomnl (totl) reltve potency IMIT Rt < Rf 9

11 ppendx IV. Free reltve potency model scrpt ; Model for effect of on reltve potences ; ths model s mde to clculte "" reltve potences from "totl" (or "nomnl") reltve ;potences for dfferent -vlues of the test lgnd whle the reference compound (estrdol) ;stys constnt. In other words: the effect of the bndng ffnty of screened compound for one ;proten on the dfference between nd totl reltve potency. RNM TIMlog RNM TRTTIMlog0 RNM TOTIMlogf RNM DTMINdmn RNM DTMdmx RNM DTOUTdout RNM DTd ; s log of bndng ffnty log00 logf9 dmn.e-6 dmx. dout d0. t6.5e-6 ; s totl proten concentrton defult t 5% FC Rt.e-6 ; s nomnl (totl) reltve potency s nom.c50 (estrdol)/nom.c50 (test lgnd) ff0.323 ; s frcton of reference (estrdol) t sme proten conc. s test lgnd defult ; s mesured vlue round nomnl C50 t 5% FC t7.76e- ; s nomnl C50 vlue of reference (estrdol) t gven proten ;concentrton fff/tot ; s frcton of test lgnd tott/rt ; s nomnl C 50 of test lgnd fff/t ; s unoccuped frcton of proten 0.00**log f(.0-(*f)/(.0*f))*t RfRt*(ff/ff) ; s conc. of unoccuped proten ; s reltve potency GU ftot/2. ROOT f(.0*t/(.0*f))*f-tot IMIT f > 0. IMIT f < tot ; s conc. of test lgnd 0