Characteristics of hemolytic activity induced by skin secretions of the frog Kaloula pulchra hainana

Abstract

Background: The hemolytic activity of skin secretions obtained by stimulating the frog Kaloula pulchra hainana with diethyl ether was tested using human, cattle, rabbit, and chicken erythrocytes. The skin secretions had a significant concentration-dependent hemolytic effect on erythrocytes. The hemolytic activity of the skin secretions was studied in the presence of osmotic protectants (polyethylene glycols and carbohydrates), cations (Mg2+, Ca2+, Ba2+, Cu2+, and K+), or antioxidants (ascorbic acid, reduced glutathione, and cysteine).

Results: Depending on their molecular mass, osmotic protectants effectively inhibited hemolysis. The inhibition of skin hemolysis was observed after treatment with polyethylene glycols (1000, 3400, and 6000 Da). Among divalent cations, only 1 mM Cu2+ markedly inhibited hemolytic activity. Antioxidant compounds slightly reduced the hemolytic activity.

Conclusions: The results suggested that skin secretions of K. pulchra hainana induce a pore-forming mechanism to form pores with a diameter of 1.36-2.0 nm rather than causing oxidative damage to the erythrocyte membrane.

Figure 1

Hemolytic activity of skin secretions from Kaloula pulchra hainana tested with erythrocytes from different species: human (□), cattle (Δ), rabbit (○), and chicken (▼ ).

Figure 2

Osmotic protection against hemolytic activity using a series of polyethylenglycols (PEGs; 300, 400, 1000, 3400, and 6000 Da). Aliquots of skin secretions from Kaloula pulchra hainana (0.7, 1.4, or 5.6 μg/mL) were added to erythrocyte suspensions containing PEGs at a final concentration of 25 mM (n = 10). **p < 0.01.

Figure 3

Effects of cations (10 mM Ca²⁺, 10 mM Ba²⁺, 10 mM Mg²⁺, 1 mM Cu²⁺, and 10 mM K⁺) on the hemolytic activity of skin secretions of Kaloula pulchra hainana. Each cation was incubated with erythrocyte suspensions, following which 1.4 or 5.6 μg/mL of skin secretions was added (n = 10), *p < 0.05.