Role of cations as components of jelly coats in Bufo arenarum fertilization.

The role of monovalent (Na⁺, K⁺) and divalent (Ca²⁺, Mg²⁺) cations in Bufo arenarum fertilization was analysed. Our results showed that the highest fertilization percentages were obtained when strings of uterine oocytes (UO) were inseminated. Under these conditions, full jelly (FJ), which represents the jelly coats surrounding the oocytes at the time of deposition, contained 68.5 ± 7.0 mM Na⁺, 27.4 ± 2.4 mM K⁺, 6.3 ± 0.9 mM Ca²⁺ and 6.9 ± 0.9 mM Mg²⁺. When the strings of oocytes were washed in deionized water, these cations diffused into the liquid medium surrounding them. There was a marked similarity between the loss of Ca²⁺ in the jelly and the decrease in the fertilizability of the UO. Furthermore, the use of chelating agents of divalent cations showed the importance of the Ca²⁺ contained in the jelly. When Ca²⁺ was sequestered from the jelly coats by the addition of the chelating agents to the insemination medium as well as by pretreatment of the UO strings, a decrease in fertilization percentages occurred, this effect being dose dependent and more markedwith EGTA. These results demonstrate that the Ca²⁺ in the jelly plays a role in fertilization. Nevertheless, taking into account that during the washing of the jelly other jelly coat components were diffused and considering that the addition of Ca²⁺ to the insemination medium reverted significantly, but only partially, the loss of fertilizability of jellied UO (washed), the participation of other components in the fertilization mechanism is suggested. [ABSTRACT FROM AUTHOR]