latrunculin works in eukaryotic cells. However, research suggests that it is the unaltered form of latrunculin that causes toxic effects. Toxicity As latrunculin inhibits actin polymerization and actomyosin contractile ability, exposure to latrunculin may result in cellular relaxation, expansion of drainage tissues and decreased outflow resistance in e.g. the trabecular meshwork. Plant Latrunculin B causes marked and dose-dependent reductions in pollen germination frequency and pollen tube growth rate. Adding latrunculin B to solutions of pollen F-actin produced a rapid decrease in the total amount of polymer, the extent of depolymerization increasing with the concentrations of the toxic. The concentration of latrunculin B required for half-maximal inhibition of pollen germination is 40 to 50 nM, whereas pollen tube extension is much more sensitive, requiring only 5 to 7 nM LATB for half-maximal inhibition. The disruption of germination and pollen tube growth by latrunculin B is partially reversible at low concentrations. (<30 nM). Animal Squeezing Latrunculia magnifica into aquarium with fishes causes their almost immediate agitation, followed by hemorrhage, loss of balance and death in 4–6 minutes. Latrunculin A has been used as acrosome reaction inhibitor of guinea pig in laboratory conditions. Human Lat-A-induces reduction of actomyosin contractility. This is associated with trabecular meshwork porous expansion without evidence of reduced structural extracellular matrix protein expression or cellular viability. In high doses, latrunculin can induce acute cell injury and programmed cell death through activating the caspase-3/7 pathway. Lethal doses TDLO - Lowest Published Toxic Dose LD50 – median Lethal Dose Applications In nature, latrunculins are used by the sponges themselves as a defense mechanism, and for the same purpose are also sequestered by certain nudibranchs. Latrunculins are produced for fundamental research and have potential medical applications as latrunculins and their derivatives show antiangionic, antiproliferative, antimicrobial and antimetastatic activities. Defense mechanism Like many other sessile organisms, sponges are rich of secondary metabolites with toxic properties and most of them, including Latrunculin, have a defense role against predators, competitors and epibionts. The sponges themselves are not damaged by latrunculin. As a measure against self-toxination, they keep the latrunculin in membrane-bound vacuoles, that also function as secretory and storage vesicles. These vacuoles are free of actin and prevent the latrunculin from entering the cytosol where it would damage actin. After production in the choanocytes, the latrunculin is transferred via the archeocytes to the vulnerable areas of the sponges where defense is needed, such as injured or