Female mice were injected with various doses of colchicine before or after induced ovulation and artificially inseminated. Their eggs were recovered and prepared according to an air-dry method for the examination of chromosomes. In the unpenetrated eggs examined four and one-half to six and one-half hours after ovulation, the chromosomes were scattered throughout the ooplasm in the colchicine treated mice.
When examined four and one-half to six and one-half hours after ovulation, only 7% of 353 eggs recovered from females injected with 0.5, 1.5 or 3.0 pg of colchicine/gm body weight earlier than three and one-half hours after ovulation were penetrated, but 35% of 144 eggs from untreated females and 41% of 73 eggs from females given colchicine at three and one-half hours after ovulation were penetrated. When examined 23 to 25 hours after ovulation 32% of 76 eggs from females treated before ovulation, 87% of 93 eggs from females treated at three and one-half hours after ovulation, and 94% of 78 eggs from control females were penetrated.
In 84% of 44 penetrated eggs from treated females their chromosomes were still at metaphase I1 while the sperm head had begun its transformation. By contrast, of 42 control eggs containing transforming sperm heads, 98% displayed anaphase or telophase of the second meiotic division.
Chromosome counts of eggs at the first cleavage revealed heteroploidy ranging from the hypohaploid to the triploid condition and the absence of normal diploid eggs from treated females whereas the majority of eggs from control females displayed the diploid number of chromosomes (2x1 = 40).
Four groups of rabbit eggs were recovered from does injected with colchicine before or after ovulation. Chromosome scattering and inhibition of fertilization were not observed. I t appears that colchicine interferes with sperm penetration, the second meiotic division and normal cleavage in the mouse, but no effect was observed in the rabbit with similar dose levels.