scholarly journals Rapid inhibition of lipogenesis in vivo in lactating rat mammary gland by medium- or long-chain triacylglycerols and partial reversal by insulin

1980 ◽  
Vol 192 (1) ◽  
pp. 361-364 ◽  
Author(s):  
L Agius ◽  
D H Williamson
Keyword(s):  
Mammary Gland ◽  
Glucose Utilization ◽  
Insulin Administration ◽  
Hepatic Lipogenesis ◽  
Medium Chain ◽  
Rat Mammary Gland ◽  
Long Chain ◽  
Partial Reversal

An intragastric load of medium- or long-chain triacylglycerols inhibited lipogenesis in lactating rat mammary gland in vivo by 82 or 89% respectively. This inhibition was reversed partially by insulin administration. Long-chain triacylglycerols inhibited hepatic lipogenesis in vivo but medium-chain triacylglycerols increased it 2-fold. Glucose utilization in vitro by mammary gland acini from triacylglycerol-fed rat was normal.

scholarly journals Effect of ovariectomy on the in vitro and in vivo activation of carcinogenic N-2-fluorenylhydroxamic acids by rat mammary gland and liver

1996 ◽  
Vol 17 (11) ◽  
pp. 2411-2418 ◽  
Author(s):  
Clare L. Ritter ◽  
Kristen K. Bennett ◽  
Nancy F. Fullerton ◽  
Frederick A. Beland ◽  
Danuta Malejka-Giganti
Keyword(s):  
Mammary Gland ◽  
Rat Mammary Gland

scholarly journals Interactions of insulin, corticosterone and prolactin in promoting milk-fat synthesis by mammary explants from pregnant rabbits

1972 ◽  
Vol 129 (4) ◽  
pp. 929-935 ◽  
Author(s):  
Isabel A. Forsyth ◽  
Christopher R. Strong ◽  
Raymond Dils
Keyword(s):  
Fatty Acids ◽  
Mammary Gland ◽  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Acid Synthesis ◽  
Long Chain Fatty Acids ◽  
Medium Chain ◽  
Long Chain ◽  
Chain Fatty Acids

1. The rate of fatty acid synthesis by mammary explants from rabbits pregnant for 16 days or from rabbits pseudopregnant for 11 days was stimulated up to 15-fold by culturing for 2–4 days with prolactin. This treatment initiated the predominant synthesis of C8:0 and C10:0 fatty acids, which are characteristic of rabbit milk. 2. Inclusion of insulin in the culture medium increased the rate of synthesis of these medium-chain fatty acids. By contrast the inclusion of corticosterone led to the predominant synthesis of long-chain fatty acids. When explants were cultured for 2–4 days with insulin, corticosterone and prolactin, the rate of fatty acid synthesis increased up to 42-fold, but both medium- and long-chain fatty acids were synthesized. 3. These results show that the stimulus to mammary-gland lipogenesis and the initiation of synthesis of medium-chain fatty acids observed between days 16 and 23 of pregnancy in the rabbit can be simulated in vitro by prolactin alone. 4. When mammary explants from rabbits pregnant for 23 days were cultured for 2 days with insulin, corticosterone and prolactin, the rate of fatty acid synthesis increased fivefold, but there was a preferential synthesis of long-chain fatty acids. Culture with prolactin alone had little effect on the rate or pattern of fatty acids synthesized. 5. The results are compared with findings in vivo on the control of lipogenesis in the rabbit mammary gland, and are contrasted with the known effects of hormones in vitro on the mammary gland of the mid-pregnant mouse.

INCORPORATION OF RAT PROLACTIN INTO RAT MILK IN VIVO AND IN VITRO

1976 ◽  
Vol 70 (1) ◽  
pp. 1-9 ◽  
Author(s):  
C. E. GROSVENOR ◽  
N. S. WHITWORTH
Keyword(s):  
Mammary Gland ◽  
Trichloroacetic Acid ◽  
Milk Protein ◽  
Culture Media ◽  
Direct Relation ◽  
Excretory Organ ◽  
Rat Mammary Gland ◽  
Pituitary Prolactin

SUMMARY Rat prolactin (11 i.u./mg) was continuously infused into the circulation of urethaneanaesthetized lactating rats for 35 min at doses of either 200 or 472 ng/min. The immunoreactive prolactin in both milk and plasma rose quickly during the first 20–25 min of infusion, then stabilized at similar levels over baseline (68 and 98 ng/ml for milk and plasma, respectively, with the 200 ng/min dose and 250 and 230 ng/ml, respectively, with the 472 ng/min dose). The concentration of prolactin in plasma fell after the infusion was stopped, whereas that in the milk either did not fall at all or fell slightly to a new stabilized level. There was a rapid and extensive loss in the immunoreactivity of prolactin added to milk when rat milk was incubated in vitro (37 °C for 1–120 min) with either 600 ng/ml of extracted pituitary prolactin (NIAMDD RP-1) or unit equivalent amounts of prolactin obtained from pituitary culture media (secreted prolactin, supplied by C. S. Nicoll). Significantly greater amounts of added RP-1 prolactin were lost when it was incubated with milk obtained after 4 h than after 18 h of non-suckling. There was, however, no drop in endogenous immunoreactive milk prolactin levels (350–400 ng/ml) when rat milk was incubated with saline for 30 min. This suggests that milk prolactin obtained as a result of plasma transfer is different chemically from the milk prolactin resulting from the addition of either RP-1 or secreted prolactin to milk in vitro. Approximately 90% of 131I-labelled rat prolactin appeared in the trichloroacetic acid precipitable fraction after incubation (37 °C for 120 min) with milk obtained after 4 h of non-suckling in either the presence or absence of thiouracil (added to prevent binding of 131I or 131I-labelled fragments to milk protein). The recovery was slightly less when 131I-labelled prolactin was incubated with milk obtained after 18 h of non-suckling. These data suggest that prolactin is quickly transferred from plasma into milk in direct relation to the plasma concentration. Once there, much of it appears to be retained by the milk perhaps chemically or physically bound; there is little, if any, degradation of the hormone. We conclude that the lactating rat mammary gland may function normally as an excretory organ for prolactin.

Comparison of binding affinities of a series of oxytocin analogues to uterine and mammary gland receptors and their biological potencies

1991 ◽  
Vol 56 (4) ◽  
pp. 939-943
Author(s):  
Jiřina Slaninová ◽  
Mario Hackenberg ◽  
Falk Fahrenholz
Keyword(s):  
Mammary Gland ◽  
Guinea Pig ◽  
Biological Activities ◽  
Binding Affinities ◽  
Apparent Dissociation Constant ◽  
Pharmacological Tests ◽  
Conformational Freedom ◽  
Rat Mammary Gland

The affinity of 12 oxytocin analogues of similar structure but differences in conformational freedom and agonistic and antagonistic properties to receptors in guinea pig uterus and rat mammary gland membrane preparations was determined by competitive binding experiments using tritiated oxytocin. The values obtained for the apparent dissociation constant KD were compared to the values of biological activities from classical pharmacological tests ( uterotonic test in vitro and galactogogic test in vivo).

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