Effects of Exogenous Cortisol on the Uptake of Corticosteroids by the Isolated Perfused Guinea-Pig Mammary Gland

Peters, A. R.; Mepham, T. B.

doi:10.1677/joe.0.0800357

Cited by 3 publications

(1 citation statement)

References 17 publications

(26 reference statements)

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“…This pronounced increase cannot be ascribed solely to prolactin action because the results presented (22,23) and retain it for a prolonged period (15). Thus, the present results, showing a marked increase of mRNA<,, levels in glands incubated with prolactin alone after a preincubation with cortisol, may reflect an action of prolactin in combination with the residual cortisol.…”

Section: Resultssupporting

confidence: 42%

Absolute requirement of glucocorticoid for expression of the casein gene in the presence of prolactin.

Ganguly¹,

Ganguly²,

Mehta³

et al. 1980

Proc. Natl. Acad. Sci. U.S.A.

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Second thoracic mammary glands of immature BALB/c female mice were stimulated to pregnancy-like lobuloalveolar (LA) development after 6 days of incubation in a corticosteroid-free step I culture medium containing insulin, prolactin, estradiol, progesterone, and growth hormone. A low basal level (0.0009%) of casein mRNA (mRN4.,) sequences was detectable in the LA glands by a specific cDNA probe. Subsequent incubation of the LA glands for 3 days in medium containing insulin and prolactin or insulin and cortisol failed to elicit mRNAesn above the basal level, indicating that neither prolactin nor cortisol alone can support casein gene expression.However, an increase in mRNA. levels was observed when the 3-day incubation with insulin and cortisol or insulin and prolactin was followed by 3 days of culture in presence of insulin, prolactin, and cortisol. When a 3-day incubation with insulin and prolactin was followed by 3 days in insulin and cortisol medium, mRNAes. levels in the gland remained similar to the basal level. However, a 20-fold increase in the mRNAesn levels ensued when the LA glands were sequentially incubated for 3 days in insulin and cortisol and then for another 3 days in insulin and prolactin medium. After a preincubation in insulin and cortisol medium, the LA glands retained residual cortisol during subsequent incubation in insulin and prolactin medium, and the mRNAes. levels in these glands were related to the level of residual cortisol present. When mRNAesn and the residual cortisol level reached a minimum, addition of fresh cortisol to the medium caused a 20-fold increase in the mRNAesn levels. This indicates that cortisol is a limiting factor in insulin and prolactin medium and its presence is absolutely required for casein gene expression.The requirement that prolactin and cortisol be present for lactogenesis was delineated over 2 decades ago (1, 2). Since then, numerous studies have shown that, during lactation, a marked increase of mammary cell RNA and protein, including casein, is dependent upon stimulation by prolactin and cortisol (3, 4). We have shown that cortisol is required for the maintenance of casein-synthesizing polysomes, poly(A)+RNA synthesis, and casein mRNA (mRNAsn) accumulation in the lactating mammary gland of the mouse (5-7). Moreover, a regulatory action of the glucocorticoid on transcription of the casein gene in the mammary gland in vivo has been demonstrated (7). However, complexities in the animal limit elucidation of the discrete role of polypeptide and steroid hormones which regulate specific expression of the casein gene in breast cells.Fragments of mammary tissue from pregnant mice were demonstrated to be capable of synthesizing casein in a culture medium containing the lactogenic hormones plus insulin (8). This provided an in vitro model for studying molecular responses of the mammary cells to prolactin and glucocorticoid action in a chemically defined medium containing insulin, which is needed for viability of the mammary parenchyma in vitro (9). Subsequen...

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Section: Resultssupporting

confidence: 42%

Absolute requirement of glucocorticoid for expression of the casein gene in the presence of prolactin.

Ganguly¹,

Ganguly²,

Mehta³

et al. 1980

Proc. Natl. Acad. Sci. U.S.A.

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Retention of glucocorticoid by isolated mammary tissue may complicate interpretation of results from invitro experiments

Bolander

Nicholas

Topper

1979

Biochemical and Biophysical Research Communications

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Amino Acid Utilization by Lactating Mammary Gland

Mepham

1982

Journal of Dairy Science

219

139

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Amino acids utilization comprises two phases, cellular uptake and intracellular metabolism. The paper reviews reports on amino acid uptake in different species and at different stages of lactation and presents new data on changes at lactogenesis. The relative importance of changes in factors which determine uptake, mammary blood flow, arterial concentration, and mammary extraction, are discussed. In addition to direct incorporation into milk protein, some absorbed amino acids are an energy source and carbon precursors of other amino acids synthesized in mammary cells. Branched-chain amino acids and ornithine act as nitrogen precursors in these syntheses. Ornithine, which is derived partly from absorbed arginine, is also a precursor of spermidine, a postulated intracellular mediator of hormone action. The question of whether milk protein yield is limited by supply to the mammary gland of certain amino acids is discussed. Much evidence indicates the importance of certain essential amino acids that are transferred stoichiometrically from blood to milk. Results of experiments involving administration of exogenous growth hormone to goats are presented. Increases in milk yield and protein yield are associated with increased rates of mammary blood flow, emphasizing the role of the latter in determining uptake.

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Effects of Exogenous Cortisol on the Uptake of Corticosteroids by the Isolated Perfused Guinea-Pig Mammary Gland

Cited by 3 publications

References 17 publications

Absolute requirement of glucocorticoid for expression of the casein gene in the presence of prolactin.

Absolute requirement of glucocorticoid for expression of the casein gene in the presence of prolactin.

Retention of glucocorticoid by isolated mammary tissue may complicate interpretation of results from invitro experiments

Amino Acid Utilization by Lactating Mammary Gland

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