抄録
The effect of pregnancy on the established lactation was examined with simultaneously pregnant and lactating mice. The measurements of respiratory activity of mammary tissue slices, nucleic acids content in mammary glands and litters'growth rate were taken as indices of lactational functions. There was no significant differences in oxygen consumption and R. Q. between non-pregnantlactating and pregnant-lactating groups either at the 14th or 19th day of lactation. Total DNA content was significantly higher in mammary glands of pregnantlactating animals than non-pregnant-lactating animals. Total RNA content was also higher in pregnant-lactating group but there was no significant difference in RNA/DNA ratio between 2 groups. The litter gain and rate of growth over the periods of the 7th to 14th and of the 12th to 19th day of lactation were not significantly different between 2 groups. These results may indicate that advancing pregnancy did not exert an inhibitory effect on lactation and that the hormonal condition suitable for mammary growth can coexist with that for lactation and vice versa, at least in mice under the present experimental condition.
The author is indebted to Prof. M. Naito for his advice and interest in this experiment.
