Lactogenesis in the rat. Changes in metabolic parameters at parturition

Kuhn, Nicholas J.; Lowenstein, John M.

doi:10.1042/bj1050995

Cited by 103 publications

(63 citation statements)

References 24 publications

(11 reference statements)

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“…The increase in the concentration of glucose in the mammary gland which accompanied lactogenesis (Figs 1 and 2) is not supported by the findings of either Kuhn and Lowenstein (1967) or Murphy et at. (1973).…”

Section: Discussioncontrasting

confidence: 35%

Progesterone Control of the Initiation of Lactose Synthesis in the Rat

Nicholas¹,

Hartmann²

1981

Aust. Jnl. Of Bio. Sci.

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The in vitro incorporation of ['4C]glucose into lactose in mammary tissue, the concentration of lactose in the mammary tissue and the concentration of lactose in the mammary secretion were determined during late pregnancy and lactation in the rat. These changes were related to the decline in blood progesterone during late pregnancy. The incorporation of [,4C]glucose into lactose was detected on day 20 of pregnancy; it increased gradually until day 22 and then increased rapidly just prior to term (day 23 of pregnancy) to reach mean ± s.e.m. maximum hourly values of 12·0 ± 1· 5 cpm x 10 4 1 g by day 3 of lactation, and then declined to lower values (6· 1 ± 0·6 cpm x 10 4 /g) by day 20 of lactation. The concentration of lactose both in the mammary tissue and in the mammary secretion increased rapidly over the last 24 h of pregnancy and then more gradually after birth to reach mean ± s.e.m. maximum values of 6·85 ± 1 ·11 mg/g tissue and 43·1 ± 2·1 gil respectively on day 15 of lactation. The decline in plasma progesterone to low levels between days 21 and 22 of pregnancy preceded the rapid increase in the concentration of lactose in the mammary tissue. A similar relationship was observed between the decline in progesterone and the increase in lactose in mammary tissue in rats Caesarean-sectioned on day 19 of pregnancy, and the administration of progesterone immediately following Caesarean section significantly depressed the accumulation of lactose in the mammary tissue. The results support the involvement of progesterone withdrawal in lactogenesis in the rat and indicate that ['4C]glucose incorporation into lactose and the concentration of lactose both in the mammary tissue and in mammary secretion are useful indicators of the synthetic activity of the mammary gland.

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Section: Discussioncontrasting

confidence: 35%

Progesterone Control of the Initiation of Lactose Synthesis in the Rat

Nicholas¹,

Hartmann²

1981

Aust. Jnl. Of Bio. Sci.

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“…Similarly, Denamur (1965) found that the first appearance of lactose in sheep mammary tissue occurred 3-4 weeks before parturition. This is in contrast with the rat, where significant lactose biosynthesis and lactose synthase activity are present only 12-24hprepartum (Kuhn & Lowenstein, 1967;Kuhn, 1968;McKenzie et al, 1971 …”

mentioning

confidence: 68%

“…The activities ofphosphoglucomutase (EC 2.7.5.1), UDP-glucose pyrophosphorylase (EC 2.7.7.9) and UDP-glucose 4-epimerase (EC 5.1.3.2) were determined as described by Kuhn & Lowenstein (1967). Lactose synthase (EC 2.4.1.22) was assayed as described by Mellenberger et al (1973).…”

Section: Enzyme Analysismentioning

confidence: 99%

Metabolic adaptations during lactogenesis. Lactose synthesis in rabbit mammary tissue during pregnancy and lactation

Mellenberger

Bauman

1974

Biochemical Journal

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1. Mammary tissue, obtained from rabbits at various stages of pregnancy and lactation, was used for tissue-slice incubations to measure the rate of lactose biosynthesis and for relevant enzymic activity measurements. A biphasic adaptation in the rate of lactose synthesis and in the RNA concentration was noted during lactogenesis. 2. The first increase in the rate oflactose biosynthesis occurred between days 15 and 24 ofpregnancy. A second substantial increase was noted immediately postpartum. The overall rate of lactose biosynthesis increased 12-fold from day 24 of pregnancy to day 15 of lactation postpartum, and then decreased from 15 to 22 days post partum. 3. The RNA concentration/g wet wt. of tissue and the ratio of RNA/DNA closely represented the biphasic ability of the mammary-tissue slice to synthesize lactose. 4. Increases in the activities of UDP-glucose 4-epimerase (EC 5.1.3.2) and lactose synthase (EC 2.4

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“…The concentration of lactose in milk was measured by the method of Kuhn & Lowenstein (1967). The milk protein content was estimated by the method described by Lowry, Rosebrough, Farr & Randall (1951).…”

Section: Introductionmentioning

confidence: 99%