Progesterone Withdrawal as the Lactogenic Trigger in the Rat

Kuhn, Nicholas J.

doi:10.1677/joe.0.0440039

Cited by 181 publications

(38 citation statements)

References 39 publications

(56 reference statements)

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“…The lactose contentnt in rats shows similar change 13,14). SINHA, SELBY and VANDERLAAN15) reported that the RNA/DNA ratio increased shortly before parturition in mice to be slightly different from our present results, in which it increased after parturition.…”

Section: Discussioncontrasting

confidence: 48%

Specific 125I-Prolactin Binding in the Mouse Mammary Gland during Pregnancy and Lactation

Sakai¹,

Kohmoto²,

Shoda³

1981

Nihon Chikusan Gakkaiho

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The level of specific 125I-prolactin binding to mammary tissues was lowered by a large amount of endogenous prolactin. Weaning or preincubation of tissues minimized this effect on underestimation of the number of binding sites. Scatchard analysis showed that specific 125I-prolactin bindings to lactating mammary tissues were correlated highly with the number of binding sites, poorly to the dissociation constant (Kd) for the prolactin binding.Amounts of specific 125I-prolactin bindings increased slowly as pregnancy progressed but still remained small, increased significantly shortly after parturition and were maintained at high levels until the end of lactation. Both the lactose content and the RNA/DNA ratio changed similarly to the change in the specific 125I-prolactin binding during pregnancy and at lactogenesis.Contrarily serum concentration of lactogenic hormones from placenta and pituitary increased rapidly from 55ng/ml on day 6 to 528ng/ml on day 8 of pregnancy and were maintained at higher levels than 135ng/ml through the latter half of pregnancy.The present results suggest that the increase in prolactin receptors accompanying parturition is one of the triggers for lactogenesis. Jpn. J.

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Section: Discussioncontrasting

confidence: 48%

Specific 125I-Prolactin Binding in the Mouse Mammary Gland during Pregnancy and Lactation

Sakai¹,

Kohmoto²,

Shoda³

1981

Nihon Chikusan Gakkaiho

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“…However, Palmiter (1969b) indicated that lactose did not repress the synthesis of the A-protein (galactosyl transferase) or B-protein (a-lactalbumin) components of the lactose synthase complex of mouse mammary tissue. Kuhn (1969) has also reported that lactose does not inhibit lactose synthase activity in rat mammary tissue.…”

Section: Discussionmentioning

confidence: 95%

“…Kuhn (1969) and Denamur (1971) have suggested that progesterone acts as a repressor of milk biosynthesis before the onset of lactation. In the rabbit, the initial decline in the concentration of plasma progesterone occurs by day 21 of pregnancy (Denamur, 1971;Challis et al, 1973) which coincides with the first lactogenic stimulus.…”

Section: Discussionmentioning

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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“…In each instance administered progesterone prevents this accumulation (Kuhn, 1969; R. P. Deis & A. Alonso, quoted by Deis, 1968). The natural disappearance of progesterone before parturition is paralleled by a marked rise in the concentration of 20\g=a\-hydroxypregn-4-en-3-one in the plasma (Fajer & Barraclough, 1967;Hashimoto, Hendricks, Anderson & Melampy, 1968;Wiest, Kidwell & Balogh, 1968;Kuhn, 1969), due to the appearance of 20\g=a\-hydroxysteroiddehydrogenase in ovarian corpora lutea ; N. J. Kuhn & M. S. Briley, to be published).…”

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confidence: 97%