Characteristics of drugs that penetrate the preimplantation blastocyst

Abstract

Experiments were performed to evaluate the role of physicochemical properties of drugs and chemicals in determining their passage into the preimplantation blastocysts of 6-day pregnant rabbits. It was found that compounds with molecular weight less than ouabain (mol. wt 585) readily traversed the blastocyst, whereas the blastocyst was relatively impermeable to those with molecular weight greater than 5000. However, for compounds with small molecular weights (100-300), the blastocyst/plasma radioactivity ratios varied considerably (0.001-1.24), suggesting that factors other than molecular weight played a role in determining their passage. Further experiments revealed that there was no correlation between blastocyst/plasma radioactivity ratio and degree of protein binding of the drugs. It was concluded that the degree of ionization and lipid solubility of the compounds are important factors in determining their rates of penetration into the preimplantation blastocysts. These findings prove that a variety of foreign compounds can enter the blastocyst during the preimplantation stages of gestation and their rates of penetration are governed by the possible interactions among their physicochemical properties. The lexicological implications of these findings were also discussed. © 1980.