Reduction of embryotoxicity by protein in embryo culture media

Abstract

Experiments tested the hypothesis that one role of protein in embryo culture media is protection of embryos against potentially embryotoxic substances in the media. Mouse embryos were cultured in modified Krebs-Ringer bicarbonate medium and in modified Tyrode's medium, aliquots of which were supplemented with 4 mg/ml of the protein bovine serum albumin (BSA), while other aliquots were left protein free. The media were prepared using water samples that differed in purity, as reflected by differences in conductivity, with tap water being least pure (and considered to have the greatest potential for being embryotoxic) and water that had been purified by reverse osmosis, Milli-Q filtration, and triple distillation being most pure. Embryos were placed in the media while in the two-cell stage of development and their development was assessed after 24, 48, and 72 hr of culture. Rate of embryo development in BSA-supplemented media was greater than that in protein-free media only when the media were prepared with the least purified water samples. Because these water samples would have contained substances not contained in media prepared with purer water, or would have contained the substances in higher concentration, the data supported the hypothesis that protein can protect embryos during culture by negating effects of embryotoxic substances in the media.

In Vitro Developmental Competence of in Vitro-Matured Bovine Oocytes Fertilized and Cultured in Completely Defined Media1

“…Although BSA has been known to effect the sperm acrosome reaction [47], the precise mechanism remains unclear. During the acrosome reaction, BSA might act as a metal ion chelator [27,28,48]. It has been suggested that D-penicillamine, L-histidine, and L-cysteine are able to capacitate hamster spermatozoa in the absence of exogenous proteins [48]; D-penicillamine was found to be the most competent divalent cation chelator for bovine spermatozoa [39].…”

“…However, serum was found to have a biphasic influence on development of bovine embryos, being deleterious to the first cleavage division but stimulatory for blastocyst development [11,26]. In early mouse embryo experiments, BSA ameliorated water quality when embryotoxicity was a problem [27]. BSA may be contaminated with several extraneous peptides, energy substrates, and growth factors [28,29].…”

Effects of glucose and protein sources on bovine embryo development in vitro

“…1995 , which are minimized by incorporating serum albumin into the culture media, due in part to its ligand binding properties protecting against toxic components of the media Ž . Flood and Shirley, 1991;Maurer, 1992 . Ž .…”

In Vitro Fertilization

“…Furthermore, albumin can negate the effects of toxins (201). The addition of a macromolecule such as serum albumin prevents gamete and embryos from becoming ''sticky'' whereby their surface charges make them stick to both glass and plastic.…”

“…The apparent contradiction of these studies can be resolved by taking into account the different stages of development used at the start of culture, the types of media used, and the supplementation of medium with protein. Albumins can chelate potential embryotoxins and thereby mask the effect of any present in the culture medium (154,201). The latter medium contains amino acids, which may chelate any possible toxins present in the tap water, e.g., heavy metals.…”