Učinak terapije kelirajućim spojevima na toksikokinetiku anorganske žive u štakora različite dobi : doktorska disertacija - Prester, Ljerka; Blanuša, Maja; Plavšić, Franjo; Jalšenjak, Ivan (Zagreb : Lj. Prester, 1995)
Sažetak: Cilj ovog rada bio je ispitati kinetiku anorganske žive (203Hg(NO3)2) u razdoblju gestacije i laktacije, te primjenu terapije kelirajućim spojevima: monoizoamilnim esterom dimerkaptojantarne kiseline (Mi-ADMS) i dimerkaptojantarnom kiselinom (DMSA) u štakorica. U razdoblju gestacije-ispitana je raspodjela žive u posteljicu i fetus u ranom i srednjem razdoblju graviditeta (između 8. - 13. dana gestacije), te djelovanje Mi-ADMS i DMSA na sniženje retencije 203Hg. U razdoblju laktacije-ispitan je prolaz anorganske žive kroz mliječnu žlijezdu u mlijeko mjerenjem retencije 203Hg u cijelom tijelu sisančadi tijekom 7 dana, te djelovanje Mi-ADMS i DMSA na sniženje retencije 203Hg u laktirajućih ženki i njihove sisančadi.Radioaktivni izotop žive 203Hg primjenjen je gravidnim ženkama i.v., a ženkama u laktaciji i.p.
Učinkovitost terapije s novim kelirajućim spojem Mi-ADMS na sniženje retencije 203Hg uspoređena je s djelovanjem DMSA koja se već primjenjuje u humanoj praksi. Terapija s kelirajućim spojevima primjenjena ja kao rani tretman: gravidnim ženkama (3 puta) u ukupnoj dozi od 1,5 mmol/kg tjel. težine (p.o.), a ženkama u laktaciji 2 puta u ukupnoj dozi od 1,0 mmol/kg tjel. težine (i.p.). Radioaktivnost 203Hg mjerena je u cijelom tijelu, organima i ekskretima (stolica i mokraća). Rezultati su izraženi kao % od primjenjene doze 203Hg, a značajnost razlike među skupinama testirana je analizom varijance (Duncanov test). Retencija 203Hg mjerena je u pojedinim organima gravidnih ženki 5. dana nakon primjene izotopa.
Rezultati ovoga rada pokazuju da je retencija 203Hg u posteljici 7 puta veća nego u fetusima, jer se u posteljici anorganska živa nakuplja, premda jedan dio 203Hg ipak prolazi placentarnu barijeru. Nakon primjene Mi-ADMS, retencija 203Hg u posteljici i fetusima je 13-14 puta, a nakon primjene DMSA 2 puta manja nego u kontrolnoj skupini. U gravidnih ženki najveća je retencija 203Hg u bubregu (38%), a u ostalim organima je mnogo manja (u probavilu, jetri i mozgu retencija 203Hg iznosi u nizu 4,04, 1,84 i 0,05% od doze). Retencija 203Hg u bubrezima, jetri i mozgu gravidnih ženki nakon promjene Mi-ADMS je u nizu 50, 9 i 7 puta manja,a nakon primjene DMSA 3, 2 i 1,2 puta manja nego u ženki kontrolne skupine.
Eliminacija 203Hg iz cijelog tijela gravidnih ženki nakon primjene Mi-ADMS je 7 puta brža (t1/2 iznosi 1 dan), a nakon primjene DMSA je 5 puta brža (t1/2 iznosi 1,5 dan) nego u kontrolnoj skupini (t1/2 iznosi 7 dana). Prolaz 203Hg kroz mliječnu žlijezdu u štakoričino mlijeko ispitan je mjerenjem retencije 203Hg u cijelom tijelu sisančadi. Ženke u laktaciji primile su 8. dan nakon okoćenja 203Hg, a sisančad je mlijekom tijekom 7 dana unosila u organizam radioaktivni izotop. Izlučivanje 203Hg štakoričinim mlijekom u leglo sisančadi od 6 životinja tijekom tog perioda iznosila je 3% od ukupne doze koju su primile ženke. Retencija 203Hg u cijelom tijelu 15-dnevne sisančadi tijekom prvih četiri dana sisanja majčinog mlijeka raste 1,5 puta, a od 5. - 7. dana postiže plato.
U tom istom periodu, retencija 203Hg u cijelom tijelu laktirajućih ženki se smanjila 2 puta, jer t1/2 u laktirajućih ženki iznosi 3,5 dana. Zbog toga bi se porast retencije 203Hg u cijelom tijelu sisančadi mogao objasnit većom apsorpcijom iz probavnog trakta i sporijom eliminacijom 203Hg u sisančadi nego u odraslih životinja. Rezultati ovoga rada pokazuju da sisančad ima drugačiju raspodjelu 203Hg od laktirajućih ženki. U sisančadi se najveći dio 203Hg nakuplja u probavilu, a u laktirajućih ženki u bubregu. Ženkama u laktaciji primjenjena je terapija s kelirajućim spojevima i ispitana njihova primjena na sniženje retencije 203Hg u štakorica i u njihove sisančadi.
Primjena Mi-ADMS smanjila je retenciju 203Hg u bubrezima laktirajućih ženki 39, u cijelom tijelu 21 puta, a primjena DMSA u cijelom tijelu i svim organima 2-3 puta u odnosu na kontrolnu skupinu. U jetri, probavilu, koži i mozgu retencija 203Hg je nakon primjene Mi-ADMS od 5-10 puta, a nakon primjene DMSA 2 puta manja nego u kontrolnoj skupini. Retencija 203Hg u cijelom tijelu sisančadi čije su majke primile Mi-ADMS je 3 puta, a u sisančadi DMSA skupine 2 puta manja nego u kontrolnoj skupini. U ostalim organima sisančadi (jetra, bubrezi, probavilo, koža, mozak) retencija 203 Hg je nakon primjene Mi-ADMS 2-3 puta, a nakon primjene DMSA oko 1,5 puta manja nego u kontrolnoj skupini.Ukratko, rezultati ovog rada pokazuju da jedan dio anorganske žive prolazi kroz placentarnu barijeru u fetus, kao i kroz mliječnu žlijezdu u štakoričino mlijeko.
Zbog toga u mladih organizama koji su pre- i postnatalno izloženi živi postoji rizik od nakupljanja 203Hg. Smanjenje retencije 203Hg u fetusima i sisančadi čije su majke primile terapiju s kelirajućim spojevima posljedica je smanjenja retencije 203Hg u cijelom tijelu ženki. Primjena Mi-ADMS značajno jače smanjuje retenciju 203Hg u laktirajućih i gravidnih ženki od DMSA, što se odražava i u fetusima i sisančadi. Ustanovljeno je da bi Mi-ADMS mogao biti učinkoviti lijek u terapiji trovanja anorganskom živom u razdoblju graviditeta i laktacije. Zbog toga novi kelirajući spoj, Mi-ADMS zavrijeđuje daljnju pozornost istraživača.
Summary: The aim of this study was to investigate the kinetics of inorganic mercury (203Hg(N03)2) and efficiency of chelation therapy with monoisoamyl meso-2,3-dimercaptosuccinate (Mi-ADMS) and meso-2,3-dimercaptosuccinic acid (DMSA) in rats in periods of gestation and lactation. Period of gestation-placental transfer of 203Hg from pregnant dams into foetuses during early and mid-gestation (between day 8 and 13) was studied. The efficiency of chelation therapy with Mi-ADMS and DMSA on reducing retention of 203Hg in whole body and organs was measured in both pregnant dams and foetuses. Period of lactation-transfer of 203Hg from mothers to their sucklings through breast milk during 7 days was studied. The efficiency of Mi-ADMS and DMSA on reducing retention of 203Hg in the whole body and organs of lactating dams and their sucklings was measured.
Pregnant rats were given a single iv injection, and lactating rats ip injection of 203Hg. Kinetics of 203Hg in whole-body of pregnant and lactating rats was analysed by calculating the half-time clearance.The efficacy of new chelating agent Mi-ADMS was compared with DMSA which is in use as antidote for reducing body burden of mercury in humans. Pregnant dams were treated with either DMSA or Mi-ADMS on three consecutive days (0.5, 24h and 48h after 203Hg administration) at the dose of 0.5 mmol/kg bw each. Lactating rats received two treatments either with DMSA or Mi-ADMS on two consecutive days (0.5 and 24h after 203Hg injection) at the dose of 0.5 mmol/kg bw each. Radioactivity of 203Hg was measured in whole body, organs, foetuses and excreta (feces and urine). Results were expressed as percent of administered 203Hg dose.
Statistical difference between groups was evaluated by analysis of variance (Duncan's test). The fifth day after application of 203Hg to the pregnant rats, the retention of isotope was measured in the whole body, organs (kidney, liver, brain, gut), placenta and fetuses. Results show significantly higher retention of 203Hg in the placenta (7 times) than in the foetuses, since inorganic mercury accumulates mainly in the placenta. However, results show that small amount of 203Hg transfer across the placental barrier in the foetus. The retention of 203Hg in both placenta and foetuses after treatment with Mi-ADMS and DMSA is 13-14 times and 2 times reduced compared to control, respectively. The highest retention of 203Hg in pregnant rats was found in the kidney (38% of the dose). In other organs it is much lower.
Gut,liver and brain have following retentions in decreasing order: 4.04, 1.84 and 0.05% of the dose. Treatment with Mi-ADMS caused a reduction of 203Hg retention in the kidney, liver and brain by factor of 50, 9 and 7 times compared to control, respectively. DMSA was less efficient in reducing corporal retention of mercury than Mi-ADMS. It reduced retention of 203Hg in the same organs by factor of 1-3. The biological half-time of 203Hg in whole body of control group of pregnant rats was found to be 7 days, and for animals treated with Mi-ADMS or DMSA 1 and 1.5 day,respectively.In this study,the rate of 203Hg transfer from lactating dams to their sucklings via breast milk was also studied.Kinetics of 203Hg retention in sucklings exposed only postnatally was measured in order to get more information about the rate of cumulation from breast feeding.
Dams were given injection of 203Hg eight days after parturition and sucklings were exposed to 203Hg via breast milk for seven days. During this period, the loss of 203Hg via milk account for about 3% of the dose given to mothers. At 4 days postdosing 203Hg to dams, whole body retention of 15-day old sucklings increased 1.5 times and between days 5-7 retention of 203Hg reaches the plateau. In lactating dams, whole body retention of 203Hg at 4 days postdosing is two-fould reduced, since the half-time for lactating dams is 3.5 days. Therefore, the increase of body retention of 203Hg in sucklings could be explained by higher apsorption in intestine and by slower elimination of 203Hg from sucklings compared to lactating dams. Different distribution of 203Hg was also found in sucklings compared to dams.
Organ retentions were in decreasing order: gut,liver,pelt, kidney and brain and in dams were: kidney,pelt,gut,liver and brain. The efficiency of chelation therapy with Mi-ADMS or DMSA (applied only to lactating dams) on reduction of 203Hg retention in both lactating dams and sucklings was also studied. Treatment with Mi-ADMS showed statistically higher reduction of whole body and kidney retention of lactating dams (21 and 39 times) than DMSA treatment (3-4 times) compared to controls. In liver, gut, pelt and brain treatment with Mi-ADMS caused reduction of 203Hg retention 5-10 times, while treatment with DMSA 2 times compared to control. Treatment with Mi-ADMS applied to lactating dams, reduced the retention of 203Hg in the whole body and organs (liver, kidney, gut, pelt and brain) of their sucklings about 2-3 times compared to control.
DMSA reduced 203Hg in above organs 1-2 times compared to control. Treatment with DMSA was found to be statistically less efficient than Mi-ADMS. In conclusion, inorganic mercury crosses the placental barrier, accumulats in the foetus, and is also excreted via mothers milk to sucklings. Even with a very low exposure of sucklings with inorganic mercury, the cumulative dose from the breast feeding is significant. Therefore, the developing foetus and sucklings could be at risk from inorganic mercury accumulation. The efficiency of Mi-ADMS treatment was generaly higher in pregnant, lactating rats and sucklings than efficiency of DMSA treatment. Furthermore, Mi-ADMS is so far the best antidote in mobilizing inorganic mercury in pregnant and lactating females as was previously estimated for 6-days and 7-week old female rats.
Therefore, this newly sintethised chelating agent deserves further scientific attention.
Doktor medicinskih znanosti - farmacija
mentor: Maja Blanuša; Komisija za ocjenu: Franji Plavšić, Maja Blanša, Ivan Jalšenjak; Komisija za obranu: Franjo Plavšić, Maja Blanša, Ivan Jalšenjak; datum obrane: 12.10.1995.; datum promocije: 10.05.1996.
Sveučilište u Zagrebu, Farmaceutsko-biokemijski fakultet, Zagreb, 1995
Bibliografija: str. 109-129
Summary
Keywords: Otrovanja -- Živa -- Detoksikacija