Sex differences in the pharmacological activity of venom from the white-tailed spider (Lampona cylindrata)

This study compared the pharmacological activity of venom from male and fem ale white-tailed spiders (L. cylindrata). In guinea-pig ileum, male L. cyli ndrata venom (1-10 mu g/ml) caused dose-dependent contractions. The respons e to venom (5 mu g/ml) was significantly inhibited by mepyramine (0.5 mu M) . Venom (550 mu g/ml) from female L. cylindrata had no contractile activity in this tissue. However, female L. cylindrata venom (50 mu g/ml) inhibited electrically-evoked twitches of guinea-pig ileum. This inhibitory effect w as attenuated by 8-phenyltheophylline (10 mu M) or by prior exposure of ven om to adenosine deaminase. In the rat vas deferens, male (5 mu g/ml) and fe male (50 mu g/ml) L. cylindrata venom inhibited electrically-evoked twitche s. 8-Phenyltheophylline (20 mu M) significantly attenuated the response to female L. cylindrata venom, while the histamine H-2- and H-3-receptor antag onists ranitidine (10 mu M) and thioperamide (0.2 mu M) significantly atten uated the response to male L. cylindrata venom. Male L. cylindrata venom (5 -20 mu g/ml) caused dose-dependent contractions in the epididymal segment o f the rat vas deferens. The response to male L. cylindrata venom (10 mu g/m l) was significantly inhibited by prazosin (0.3 mu M) but was unaffected by depleting monoamine stores with reserpine. Male L. cylindrata venom (5-15 mu g/ml) caused dose-dependent increases in rate and force of rat atria whi ch were significantly inhibited by propranolol (5 mu M) but not by reserpin e. Female L. cylindrata venom (50 mu g/ml) had no effect in atria. In the a naesthetised (pentobarbitone, 100 mg/kg, i.p.) rat, male L. cylindrata veno m (10-300 mu g/kg, i.v.) caused dose-dependent depressor responses while ve nom (up to 1 mg/kg, i.v.) from female L. cylindrata had no effect on arteri al pressure. A histamine content of 5 and 0.01% (dry weight) was detected i n venom from male and female L. cylindrata, respectively. Venom from male L . cylindrata was found to contain 56 pg noradrenaline/mu g whereas venom fr om the female contained negligible noradrenaline. The results of this study show the presence of histamine and noradrenaline in venom from male L. cyl indrata. Although devoid of significant quantities of these amines, female L. cylindrata venom has activity at adenosine receptors. (C) 2000 Elsevier Science Ltd. All rights reserved.