In vivo effects of Buthus occitanus tunetanus and Androctonus australis garzoni scorpion venoms on pregnant and non-pregnant rats

scorpion venom; Buthus occitanus tunetanus; Androctonus australis garzoni; in vivo effects; gravid rats

SHORT COMMUNICATION

In vivo effects of Buthus occitanus tunetanus and Androctonus australis garzoni scorpion venoms on pregnant and non-pregnant rats

Hmed B. N.^I; Serria H. T.^I; Selma C.^I; Zouheir S.^I; Tarek R.^II; Mondher K.^III; Zakaria B.^IV; Mounir Z. K.^I

^ILaboratory of Pharmacology, Sfax Faculty of Medicine, University of Sfax, Tunisia

^IILaboratory of Histology and Embryology, Sfax Faculty of Medicine, University of Sfax, Tunisia

^IIIService of Communitarian Medicine and Epidemiology, CHU Hédi Chaker, Sfax, Tunisia

^IVPasteur Institute of Tunis, Tunisia

^{Correspondence to}

ABSTRACT

Scorpion envenomation in pregnant victims has been scarcely studied. Accidents with venomous animals can induce serious injuries for both mothers and embryos. In the current work, the lethality of Buthus occitanus tunetanus (Bot) and Androctonus australis garzoni (Aag) venoms was assessed in pregnant and non-pregnant murine rat models. The median lethal dose (LD₅₀) was determined following the Spearman-Karber method. Our results showed great similarities of envenomation symptoms between term-pregnant and nonmated rats. An unusual vaginal bleeding was also seen in pregnant rats envenomed with Bot and Aag venoms. Our findings suggest that gestation may increase the venoms toxicity in rats.

Key Words: scorpion venom, Buthus occitanus tunetanus, Androctonus australis garzoni, in vivo effects, gravid rats.

INTRODUCTION

Scorpion envenomation is widely spread in many regions of the world (5). In Tunisia, approximately 30,000 to 45,000 cases of scorpion-stung humans are reported every year (8). The morbidity and lethality of scorpion venoms are due to the action of different neurotoxins affecting the activity of a large variety of membrane ion-channels components (17, 18). They vary with many factors related both to the victim's state (age, body weight, strain and sex) and to the involved venomous animal (genus, geographical and seasonal distribution, and individual intraspecificity) (1, 3, 6–8, 13, 15, 16). Manifested symptoms vary from local burning to cardiorespiratory arrest, which is usually responsible for the victim's death.

Although there are numerous data on scorpion venoms and their adverse effects, scarce information has been reported about their toxicity in pregnant victims (9).

In the present paper, the toxicity of venoms from Buthus occitanus tunetanus (Bot) and Androctonus australis garzoni (Aag), two scorpion species frequently involved in human envenomation in Tunisia, were assessed in late primigravida Wistar rats by determining the LD₅₀ and recording the envenomation symptoms.

White Wistar virgin female rats were used. Each six rats were bred in a separate cage at the animal house of the Laboratory of Pharmacology, University of Sfax, Tunisia. The conditions at the animal house were kept constant with temperature of 23–25°C and light-dark cycle of 14 light : 10 dark cycles. Drinking water and standard food were provided ad libitum. After one week of acclimatization, females were allowed to mate with mature males in order to obtain timed-pregnant rats. The day in which spermatozoa appeared in the vaginal smear was considered the first day of pregnancy. In such conditions, fetal delivery may occur 21±1 days post coitus. Non-pregnant rats were kept under the same conditions.

Buthus occitanus tunetanus and Androctonus australis garzoni crude venoms were obtained from the Pasteur Institute of Tunis, Tunisia. They were collected by electrical milking, then water-extracted, freeze-dried, and finally rehydrated, according to the method of Miranda et al. (12). On the experiment day, venoms were adequately diluted with physiologic saline solution in order to obtain four different doses (0.5, 1, 2, or 4mg/ml of total proteins for Bot venom and 0.19, 0.37, 0.75, or 1.5mg/ml for Aag venom).

The median lethal dose (LD₅₀) was determined according to the method of Spearman-Karber (4) for both pregnant and non-pregnant rats. Briefly, a group of six mated or nonmated rats received one of the prepared crude venom doses in order to obtain four dose points in the response curve (animal mortality) within the linear portion, covering the full response range from 0% to 100% during 24h after the venom intraperitoneal injection. To prevent body weight-induced variability of the venoms effects, the administered volume was kept constant at 1ml/kg of body weight (BW). Crude venom doses were intraperitoneally injected. Almost all tests on pregnant and non-pregnant rats were carried out at the same day (corresponding to the 22^nd day of gestation). The BW on the experiment day was 370±15g for pregnant rats and 273±14g for non-pregnant rats. Envenomation symptoms were recorded for each group during the experimental period.

The LD₅₀ was lower in pregnant (472µg/kg for Aag venom and 1.587µg/kg for Bot venom) than in non-pregnant (595µg/kg for Aag venom and 1.781µg/kg for Bot venom) rats (Table 1).

Similar envenomation symptoms (squeaking, mouth rubbing, salivation, chewing, agitation, respiratory dysfunction, loss of equilibrium, and paralysis) were observed in both pregnant and non-pregnant rats (Table 2). An unusual vaginal bleeding manifested in pregnant rats for both Aag and Bot envenomation. At high venom doses (2mg/kg and 0.75mg/kg for Bot and Aag, respectively), fetal delivery was observed before the animal death.

To our knowledge, few studies have focused on the toxicity of scorpion venoms in gravid females. Elsewhere, a teratogenic chronic effect of scorpion venom was observed in pregnant rats (6). In this work, the toxicity of two scorpion species frequently involved in human envenomation in Tunisia was investigated in murine gravid model. Our results showed great similarities of envenomation symptoms between pregnant and nonmated rats. Such signs are mainly observed in scorpion envenomation victims (5). However, an unusual vaginal bleeding, a sign of ongoing labor, was seen when high venom doses were used in term-pregnant rats. Uterine contractility is a key process of parturition. Thus, such effects may be a result of the direct venom-induced hypercontractility of the uterine myometrium (10, 11, 14). The LD₅₀ of Bot venom in term- and non-pregnant rats was higher than that obtained by Devaux and Rochat (2) in non-pregnant mice (1,428µg/kg). However, the LD₅₀ of Aag venom was similar to that of its congener Androctonus australis, whose lethality ranged from 0.32 to 0.7mg/kg. The scorpion venom lethality (LD₅₀) increases with the increase in body weight (7, 8, 13, 14), but herein a controversial result was observed. Pregnant rats weighing more than non-pregnant rats (370±15g and 273±14g, respectively) presented a lower LD₅₀. Thus, we can suggest that gestation may increase female sensitivity to scorpion envenomation.

In conclusion, females may be more vulnerable to scorpion envenomation during gestation. In the present study, envenomation may have disturbed the pregnancy process, corroborating the data on other venomous animal bites and stings.

Received: May 2, 2007

Accepted: July 2, 2007

Abstract published online: August 8, 2007

Full paper published online: March 8, 2008

Conflicts of interest: There is no conflict.

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Publication Dates

• Publication in this collection
  16 June 2008
• Date of issue
  2008

History

• Received
  02 May 2007
• Accepted
  02 July 2007