I wish to expose fish embryos to phenethyl isothiocyanate (PEITC). As an oil, I assume that I should first dissolve it in alcohol before making up assays. Does anyone know if this is the case, and if so, what sort of ratio of PEITC to alcohol should be used?
I wanted to answer, but due to insufficient knowledge I could not. However, i found one very similar article: Toxicity to T etrahymena and abiotic thiol reactivity of aromatic isothiocyanates .
Link: http://link.springer.com/article/10.1007/s10565-005-0169-3
Hope it helps!
The experiment you will be doing is not so obvious. The compound has a logP of 3.5 and hence will hardly or not dissolve in water. SStarting from an ethanol (DMSO would be better) solution will NOT increase the water solubility unless the solvent in water concentration is really high. In any case you would be exposing your embryos to a mixture. A solvent control will not completely correct this as you might be confronted with mixture effects (synergism, antagonism, potentiation, ....) Moreover the high logP will cause your compound to prefer the plastic of the microtiterplates instead of the water phase. A better approach is to use a passive dosing system. See reference:
Vergauwen L, Schmidt SN, Stinckens E, Maho W, Blust R, Mayer P, Covaci A & Knapen D (2015) A high throughput passive dosing format for the Fish Embryo Acute Toxicity test. Chemosphere 139: 9-17.
Thank you for your generous input, Freddy and Jaspreet.
Freddy, I have read some papers concerning the toxicity of various solvent carriers to developing fish, and have come to the conclusion that DMSO is indeed the best choice for me. My current plan is to dissolve PEITC into DMSO at a ratio of 1 part PEITC to 10 parts DMSO. I shall put the resulting stock under a dissection microscope to ensure that there are no oil bubbles left, and if there are, I shall increase the DMSO. I then plan to add the stock to water at a ratio of about 1:100 and then freeze the resulting stock into Eppendorf tubes at known volumes of PEITC and solvent ready for my experiments. I'm not using microtitre plates, so the paper you kindly linked to is not going to be of use unless I change the experimental set up, which it is a little late in the day for. I am raising eggs to just before exogenous feeding in beakers of water. To make up the water used in the treatments, I will add the stock from the eppendorfs to litres of water to arrive at the concentrations desired. I hope that the PEITC will disperse evenly through the water phase. Should there be problems, I may have to consider the passive dosing approach. The problem with that is, some of the fish eggs used (salmonids) will take many weeks to hatch and will need to be kept chilled and well aerated. I'm not sure this would be possible with the design outlined in the paper.
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