Exposure of tilapia pituitary cells to saponins: Insight into their mechanism of action

Cell permeation and durable effects of triterpenoidal saponin preparations from soybean (SbS), Quillaja saponaria Molina (QsS) and Gypsophila paniculata (GypS), were studied. A concentration-dependent change in hemolysis rates was observed when cells were incubated with QsS or GypS, but not with SbS. Dose dependence was also observed for the leakage of lactate dehydrogenase (LDH; MW 142,000) and of Luteinizing Hormone (LH; MW 35,000) from tilapia pituitary dispersed cells. Exposure of pituitary fragments to a combination of GnRH and GypS or QsS, resulted in a significantly high release of LH. GypS were shown to be more potent in inducing hemolysis of human RBC's and LH release from tilapia pituitary fragments. Interestingly, tilapia pituitary fragments treated with QsS were able to secrete LH in a characteristic manner, in response to a second Gonadotropin Releasing Hormone (GnRH) pulse, while fragments exposed to GypS did not respond to the second hormone pulse. The rapid recovery of pituitary fragments after the removal of QsS, may suggest a rearrangement of membranes rather than pore formation as the mechanism of action of QsS. Understanding the structural features underlying the reversible rearrangement of membranes and the lack of hemolysing activity by specific saponins may lead to the development of novel bioactive drugs.