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has been recorded by many authors (SALOMI etal., 1992). Moreover it has been reported to in-hibit eicosanoid generation in leucocytes and non-enzymatic peroxidation in ox brain phospholipidsliposomes (HOUGHTON et al., 1995) and protectorgans against the oxidative damage induced by avariety of free radicals (BADARY et al., 1997; NAGIet al., 2000).

In this study we investigated the effect of

Nigella sativa extract on the DNA synthesis, cellproliferation and the ability of scavenging super-oxide radicals in mice bearing tumor cells. Moststudies of N. sativa treatments against tumorshave been conducted by intraperitoneal injectionin vivo or direct addition to isolated cells in vitro.Humans normally consume N. sativaorally. There-fore, a study has been conducted to investigate theantitumor effects ofN. sativaextract when admin-istered orally to mice bearing the Ehrlich ascitestumor (EAT).

Material and methods

Animals

Adult Balb/C male mice weighing 22 2 g were ob-tained from DETAM (Experimental Medical ResearchCenter, Capa Medical College, Istanbul, Turkey). Themice were maintained as 6 animals per cage in 12h/12hdark/light cycle under normal laboratory condition oftemperature and humidity, fed with rodent pellets andtap water ad libitum.

Tumor cells

Ehrlich ascites tumor (EAT) described in this paperwas hyperdiploid subline (obtained from Istanbul Uni-

versity, Department of Biology, Turkey), which hasbeen propagated in our laboratory by weekly intraperi-toneal inoculation of about 106 cells/mouse. Unlessotherwise indicated, the EAT was obtained from donormice on the sixth day of tumor growth. The ascites tu-mor cells, obtained from donor mouse, were dilutedwith buffer solution saline (BSS) and counted withhaemocytometer.

Plant material

N. sativaseeds were purchased from the local herbalistin Sanliurfa. The seeds were botanically authenticatedby a specialist of plant taxonomy in biology depart-ment. A specimen has been preserved at 4 C. The seedswere identified, cleaned, dried, mechanically powdered

and extracted with 96% ethanol and evaporated withrotary evaporator to render the extract alcohol free.The extract was kept in a domestic refrigerator at 4 C.

Experimental design

For this study, forty adult healthy male mice were usedand randomly divided into two equal groups. EAT cellscollected from peritoneum of tumor-bearing mice werediluted with BSS, and counted using Neubauer haemo-cytometer. The final cell number was 3105/cells/mL.Each animal in the groups was inoculated with 3105

cells intraperitoneally on 0 day and treated as follows:

Group I: Each mouse received orally 1 g/kg/dayNSE suspended in 10 mL of 5% gum arabica in normal

saline by gavage for 7 days (the final concentrationwas 10 mg/0.1 mL). The optimum oral dose of NSEwas 0.88 g/kg body weight. This corresponded to theoptimum effective dose of NSE in treatment of stomachulcers (EL-DAKHAKHNY et al., 2000).

Group II: Each mouse received orally 0.2 mL/dayvehicle (5% gum arabica in normal saline) suspension,for 7 days and served as control.

At 2, 4, 6 and 8 day intervals, 5 animals from eachgroup were injected intraperitoneally with 20 Ci tri-tiated thymidine (3H-TdR) (Perkin Elmer Life ScienceInc., Boston, MA 02118 USA) 30 minutes before sac-rificing the mice. Immediately after death, cells wereflushed from the peritoneum of each animal into aknown volume (20 or 50 mL) of heparinized normalsaline by repeated injection and withdrawal of 3-5 mLvolumes. Cancer cells were recognized and counted us-ing Neubauer haemocytometer. The mean cell numberfor each group of 5 animals is shown in Figure 1. Asciticfluid with EAT was smeared on clean slides, air driedand fixed in Clarkes fixative (PEACOCK, 1973). Threeslides were processed for autoradiography according tothe method described by ROSE & ROSE (1965), andthree slides processed for evaluation of mitotic index.For autoradiography, 3 slides were prepared by the dip-coating method using Kodak emulsion (Eastman Ko-dak Company, N.Y., USA). The exposure time was 7days and developed in Kodak D 19 b developer. Theuptake of thymidine by EAT cells was expressed asa percentage of labeled tumor cells, determined, foreach animal, on 1000 10 cells/smear at random. Thelimits of accuracy of the cell count were obtained bydetermining the percentage of labeled tumor cells inautoradiographs of smears prepared from the same as-citic fluid sample. Because the total number of cellscounted was the same in each case, statistical analysis(t-test) was made between the means of the numberof labeled cells. It was assumed that EAT cells labeledwith 3H-TdR had synthesized DNA (PAINTER et al.,1960).

Survival time

Thirty adult male mice randomly divided into threegroups (A, B, and C; n = 10) were used for this study.Each mouse was inoculated with 3105 EAT cells sus-pended in BSS on day 0. Each mouse in the groups Aand B was orally treated with 1 g and 2 g NSE/kg/day,

respectively, while that in the group C (control) wasorally administered 0.2 mL/day gum arabica vehicle.Treatment with NSE (1g/kg and 2g/kg body weight)

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and vehicle orally using catheter fixed to 1 mL stan-dart syringe was started 24 hours after EAT inocu-lation. Daily treatment continued until the last deadmouse in the control group was recorded (this periodwas found to be 15 days). Median survival time for thethree groups was evaluated. The animals surviving 35days were considered to be cured. All surviving ani-mals were sacrificed at the end of the experiment, tocompare the tumor efficacy of NSE (1g/kg and 2g/kgbody weight) and the histopathological changes. The

viable tumor cell counts (trypan blue test) were carriedout with Neubauer haemocytometer.

Lipid peroxidation (LPO)Lipid peroxidation was determined by measuringthe thiobarbituric acid reactive substances (TBARs)formed by the thiobarbutiric acid (TBA) reaction ac-cording to JO & AHN (1998), using spectrofluorometerwith 520 nm excitation and 550 nm emission.

Glutathione level (GSH)The total GSH was determined according to themethod of BROWNE & ARMSTRONG (1998), using aspectrofluorometric method with 350 nm excitationand 420 nm emission.

Statistical analysisAll data are expressed as means SD. The data wereanalyzed using the Student t-test; differences were con-sidered significant when p < 0.05.

Results

Tumor growthStudies on the effect of ethanol extract ofNigellasativa on tumor growth were monitored. It wasfound that 1g/kg body weight of extract orally ad-ministration by gavage could inhibit the cell pro-liferation at 2, 4, 6, and 8 days, respectively, com-pared with the corresponding cell numbers in thecontrol group (Fig. 1). The viable tumor cell num-

ber was found significantly inhibited (p < 0.001)in treated groups. The percentage of trypan blue-positive dead tumor cells were also increased in thetreated groups compared with the controls; espe-cially more pronounced effects were observed at6th and 8th days.

Cytological studies using Feulgen and Giemsastaining methods have revealed a significant (p