Lecture 14 - Lactation Part 2 Flashcards
Why does the mammary epithelium have a high mitochondrial density
ATP for synthetic processes
Uptake precursors, transport into lumen
How much arterial blood oxygen does the mammary epithelium consume
50%
What does the rough endoplasmic reticulum of the mammary epithelium do
Make proteins (ribosomes)
What do the smooth endoplasmic reticulum of the mammary epithelium do
Make phospholipids and triglycerides (fat droplets)
(f.a. synthesis and glycolysis in cytosol)
What does the golgi do in mammary epithelium
Synthesizes lactose
Lactose synthase = glucose+galactose
Where does glucose for lactose synthesis come from
Starch and sugar digestion/absorption in monogastrics
Ruminants main source is propionate and glucogenic aa converted in the liver
Where does galactose for lactose synthesis come from
Conversion of glucose
The main determinant of milk secretion is
Lactose
Decrease in blood glucose leads to
Decrease of lactose and milk volume
What turns on the enzymes for lactose production
Prolactin
Milk fat is made up mostly of
98% triglycerides
How does the mammary get free fatty acids
From chylomicrons or VLDL
OR de novo f.a. synthesis in alveolar epithelial cells
Fatty acids can be made from… (monogastric vs ruminant)
Glucose, acetate and ketone bodies
NOT glucose in ruminants (saved for making lactose)
What happens to large lipid droplets? What else do these provide the neonate?
They are drawn to the apex of the cell
provide phospholipids, cholesterol to neonate
Slide 16**
Fats
What can non-ruminants do with regards to acetyl coa that ruminants can not
Can lyse citrate with citrate lyase in presence of CoA to produce acetyl-CoA for f.a. synthesis (make f.a. from glucose)
Ruminants do not have citrate lyase
What f.a. are in milk
C4, C6, C8, C10, C12
Slide 20
help
Milk protein is made in… Packed in…
Made in rough endoplasmic reticulum
Packaged in the golgi secretory vesicles
What proteins are in milk
Whey proteins (B-lactoglobulin and a-lactalbumin, lactoferrin)
and casein (binds minerals)
Free ions in milk:
Na, K, Cl
Second most important osmotic component of milk determining milk volume (after lactose)
Ions
How do ions get into milk
Na/K pump on basolateral membrane
Slide 23, 24
Secretion of milk components
What components are packaged in secretory vesicles in the golgi
Lactose, casein, whey proteins, citrate, Ca
How does milk fat secretion occur
Portion of apical membrane surrounds the fat droplet
How is milk production regulated
According to consumption by offspring (or milking)
Mediated by pressure in the glands
How can we increase milk production in dairy
Increase milking frequency
Give a growth hormone
Slides 25, 26
Curves
Homeorhesis vs homeostasis
Rhesis = orchestrated changes to meet the priorities of a physiological state (e.g. lactation)
Stasis = maintenance of a steady state of a given physiological function
Ways the GI tract adapts for lactation
- expansion of reticulorumen to allow for greater intake
- increase capacity of omasum, abomasum, SI
- increase LI size for more water absorption
- water absorption increases, excretion minimized
- shift in partitioning of nutrients towards mammary gland
- expansion to allow greater DMI driven by energy expense of milk production
How many volumes of blood support 1 volume of milk produced
500
How does blood volume and flow change during lactation
- plasma volume increases to accommodate demand
- potassium and sodium requirements increase
- kidney adjusts to increase water absorption
How does the liver adapt during lactation
- nutrient partitioning of CHO, protein, fat
- drains GIT and delivers absorbed nutrients
- gluconeogenesis from propionate
- glycogenolysis increases
- acetate and butyrate used as E source and substrate for f.a.
- TG synthesized in liver, exported
Why does the liver maximize glucose available to the mammary gland during lactation
Large demand for glucose for lactose production (key determinant of how much milk we can produce)
How does adipose tissue adapt to lactation
- reduced uptake of glucose (insulin sensitivity to glucose lower)
- mobilizes stored TG (priority over lipogenesis)
- leptin secretion drops as adipose mass drops (increase feed intake)
How does bone adapt to lactation
- calcium uptake at gut and mobilization from bone
- calcitonin prevents elevated calcium in blood
Glucose sparing mechanisms by the rest of the body
- acetate/propionate used for E
- no pathway for glucose use for lipogenesis
- glucose used for lactose synthesis in mammary
During lactation, mammary gland increases uptake of…
amino acids (met and lys are first limiting milk production)
free f.a. and glycerol
de novo TG synthesis from circulating SCFA
How does muscle adapt to lactation
- utilizes f.a. for E instead of glucose
- provides reservoir of aa (protein synthesis)
- growth is prioritized over milk during the first lactation
Slide 42
Preparturient E balance
Growth hormones role in lactation
High at onset of lactation (can be used to maintain milk production)
Lipolytic effects to make f.a. available
Leptins role in lactation
Produced by fat cells, as adipose accumulates, leptin increases
Declines as energy is mobilized from adipose (during lactation)
