X-Message-Number: 15835 Date: Sat, 10 Mar 2001 08:44:40 -0800 (PST) From: Doug Skrecky <> Subject: trimethylene glycol has unusually low toxicity A focus for vitrification research in the literature has been on penetrating cryoprotectants with relatively low critical warming rates. The theory has been that solutions incorporating these solvents would avoid recrystalization at lower and hopefully less toxic concentrations. Unfortunately these cryoprotectants tend to be quite toxic even at low concentrations. An alternative strategy would be to cast the net wider to include more consideration of cryoprotectants with exceptionally low toxicity, rather than the lowest critical warming rates. A clear standout in this regard is trimethylene glycol. It is the only cryoprotectant which gave no evidence of any toxic effect at the maximum dosage tested (3.1 M), as measured by rabbit spermatozoa mobility. (Incubation of spermatozoa was for 30 minutes at 20 C.) DMSO earned second place with a maximum non toxic concentration of 2.17 M. Ethylene glycol was third at 1.55 M. Lactamide, acetamide, and propionamide tied for fourth at 0.93 M. Butyramide, dimethylformamide, glycerol, and malomide proved to be yet more toxic. Glycerol has been used in vitrification solutions. The critical warming rate for trimethylene glycol is about the same as for glycerol (see Cryobiology 40: 151-158 2000). I suspect that replacing glycerol in vitrification solutions with trimethylene glycol would reduce vitrification solution toxicity significantly. Note: The medline abstract below unfortunately hides trimethylene glycol's exceptional property. _______________________________________________________________ Title Cryoprotective effects of some amides on rabbit spermatozoa. Source Journal of Reproduction & Fertility. 60(1):247-52, 1980 Sep. Abstract Semen was diluted 1:9 with egg yolk-citrate medium containing 0.31--3.1 M (final concentration) formamide, butyramide, acetamide, propionamide, dimethylformamide, lactamide, malomide, ethylene glycol, trimethylene glycol, dimethylsulphoxide (DMSO) or glycerol. After 30 min incubation at 20 degrees C, sperm motility was superior in hypertonic solutions of acetamide, lactamide, dimethylsulphoxide, trimethylene glycol and ethylene glycol. Some of these compounds were added to semen diluted 1:2 in an isotonic egg-yolk-glucose-lactose-raffinose solution and frozen by the pellet method. Relatively good survival of motility was obtained in 1.0 M-DMSO, -lactamide or -acetamide. Dimethylformamide (0.5 M), ethylene glycol (0.5--1.5 M), trimethylene glycol (1.5 M) and propionamide (0.75 M) also gave some protection. Insemination of does with semen frozen and thawed with 1.0 M-DMSO, -lactamide or acetamide gave fertilization rates of 68--88%, and 84% (38/45) of does gave birth to an average of 5.3 young. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=15835