Author(s): Muhammad A ElSaadani
A peptide fraction isolated from the venom of the Egyptian scorpion Buthus occitanus was proved to have a bradykinin- potentiating activity. In vivo and in vitro modes of action of the isolated bradykinin- potentiating peptide (BPP) on kidneys of guinea pigs were investigated. Animals received five successive i.p. doses of the scorpion BPP (1 µg/g body weight) at one-week intervals. The control animals were i.p. injected with saline solution only. In vivo experiments showed a significant increase in renal tissue PGE2 content and lipid peroxides of the treated guinea pigs compared to the control animals (p < 0.05). Nonsignificant changes were detected in the levels of tissue c-AMP and 5-nucleotidase activity (p > 0.05) of the treated animals, while the changes in c-GMP and c-AMP/c-GMP ratio were both significant (p < 0.05). In vitro experiments demonstrated enhanced capacity of guinea pig-renal tissue to convert 14C-linoleic acid to its metabolites, 6-keto-PGF1α, PGF2α, PGE2, TxB2, PGD2, and arachidonic acid, in response to the added PBP (1 µg/ml) and bradykinin (1 µg/ml). This enhanced response was abolished upon the addition of 1 µg/ml of BK-inhibitor (D-Arg- [Hyp3, Thi5,6, Phe7]). The capacity for labeled metabolites recovery in BPP treated renal tissue was 19.78%, while it was 13.00% in the basal control. The total increase that evoked by BPP was 62.78%. The results clearly indicate that the isolated BPP induced prostaglandin biosynthesis, which may trigger enhanced glomerular filtration in guinea pigs.