The metabolisms in the slices from the mammary gland of lactating and nonlactating Wister rats were studied, mainly in connection with glucose or glucose-
14C consumption and the formation of
14CO
2 and
14C-lipids. The following findings were obtained.
Succinic oxidase activity was enhanced by more than 10 times in lactating than in nonlactating preparation, for Qo
2 gained were 20.60 in the former and 1.57 in the latter (
cf. Qo
2 at the end of pregnancy : 2.48). Qo
2 was decreased to 3.89 seven days after weaning.
Incorporation of radioactivities into CO
2 and lipids during incubation of the slices with glucose-u-
14C was increased by more than 10 times in lactating than in nonlactating preparations. Degree of participation of hexose monophosphate oxidative pathway in glycolysis was about 57% in lactation and less than 1% in nonlactation, respectively, as calculated from the formation of
14C-lipids in slices incubated with glucose-1-
14C or 6-
14C.
14C-lipids resulting from glucose-u-
14C was analyzed by means of gaschromatography. C 16: 0, 1 4C 18: 0 and C 18: 1 were found in 8.6, 71.0 and 20.4% of all incorporation into fatty acids, respectively. Glucose-6-phosphate dehydrogenase activity was increased by about 3.7 times during lactation, as compared with that after weaning.
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