Lecture 14 - Lactation Part 2

Question 1

Why does the mammary epithelium have a high mitochondrial density

Answer 1

ATP for synthetic processes
Uptake precursors, transport into lumen

Question 2

How much arterial blood oxygen does the mammary epithelium consume

Answer 2

50%

Question 3

What does the rough endoplasmic reticulum of the mammary epithelium do

Answer 3

Make proteins (ribosomes)

Question 4

What do the smooth endoplasmic reticulum of the mammary epithelium do

Answer 4

Make phospholipids and triglycerides (fat droplets)
(f.a. synthesis and glycolysis in cytosol)

Question 5

What does the golgi do in mammary epithelium

Answer 5

Synthesizes lactose
Lactose synthase = glucose+galactose

Question 6

Where does glucose for lactose synthesis come from

Answer 6

Starch and sugar digestion/absorption in monogastrics
Ruminants main source is propionate and glucogenic aa converted in the liver

Question 7

Where does galactose for lactose synthesis come from

Answer 7

Conversion of glucose

Question 8

The main determinant of milk secretion is

Answer 8

Lactose

Question 9

Decrease in blood glucose leads to

Answer 9

Decrease of lactose and milk volume

Question 10

What turns on the enzymes for lactose production

Answer 10

Prolactin

Question 11

Milk fat is made up mostly of

Answer 11

98% triglycerides

Question 12

How does the mammary get free fatty acids

Answer 12

From chylomicrons or VLDL
OR de novo f.a. synthesis in alveolar epithelial cells

Question 13

Fatty acids can be made from… (monogastric vs ruminant)

Answer 13

Glucose, acetate and ketone bodies
NOT glucose in ruminants (saved for making lactose)

Question 14

What happens to large lipid droplets? What else do these provide the neonate?

Answer 14

They are drawn to the apex of the cell
provide phospholipids, cholesterol to neonate

Question 15

Slide 16**

Answer 15

Fats

Question 16

What can non-ruminants do with regards to acetyl coa that ruminants can not

Answer 16

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

Question 17

What f.a. are in milk

Answer 17

C4, C6, C8, C10, C12

Question 18

Slide 20

Answer 18

help

Question 19

Milk protein is made in… Packed in…

Answer 19

Made in rough endoplasmic reticulum
Packaged in the golgi secretory vesicles

Question 20

What proteins are in milk

Answer 20

Whey proteins (B-lactoglobulin and a-lactalbumin, lactoferrin)
and casein (binds minerals)

Question 21

Free ions in milk:

Answer 21

Na, K, Cl

Question 22

Second most important osmotic component of milk determining milk volume (after lactose)

Answer 22

Ions

Question 23

How do ions get into milk

Answer 23

Na/K pump on basolateral membrane

Question 24

Slide 23, 24

Answer 24

Secretion of milk components

Question 25

What components are packaged in secretory vesicles in the golgi

Answer 25

Lactose, casein, whey proteins, citrate, Ca

Question 26

How does milk fat secretion occur

Answer 26

Portion of apical membrane surrounds the fat droplet

Question 27

How is milk production regulated

Answer 27

According to consumption by offspring (or milking) Mediated by pressure in the glands

Question 28

How can we increase milk production in dairy

Answer 28

Increase milking frequency Give a growth hormone

Question 29

Slides 25, 26

Answer 29

Curves

Question 30

Homeorhesis vs homeostasis

Answer 30

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

Question 31

Ways the GI tract adapts for lactation

Answer 31

- 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

Question 32

How many volumes of blood support 1 volume of milk produced

Answer 32

500

Question 33

How does blood volume and flow change during lactation

Answer 33

- plasma volume increases to accommodate demand - potassium and sodium requirements increase - kidney adjusts to increase water absorption

Question 34

How does the liver adapt during lactation

Answer 34

- 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

Question 35

Why does the liver maximize glucose available to the mammary gland during lactation

Answer 35

Large demand for glucose for lactose production (key determinant of how much milk we can produce)

Question 36

How does adipose tissue adapt to lactation

Answer 36

- 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)

Question 37

How does bone adapt to lactation

Answer 37

- calcium uptake at gut and mobilization from bone - calcitonin prevents elevated calcium in blood

Question 38

Glucose sparing mechanisms by the rest of the body

Answer 38

- acetate/propionate used for E - no pathway for glucose use for lipogenesis - glucose used for lactose synthesis in mammary

Question 39

During lactation, mammary gland increases uptake of...

Answer 39

amino acids (met and lys are first limiting milk production) free f.a. and glycerol de novo TG synthesis from circulating SCFA

Question 40

How does muscle adapt to lactation

Answer 40

- utilizes f.a. for E instead of glucose - provides reservoir of aa (protein synthesis) - growth is prioritized over milk during the first lactation

Question 41

Slide 42

Answer 41

Preparturient E balance

Question 42

Growth hormones role in lactation

Answer 42

High at onset of lactation (can be used to maintain milk production) Lipolytic effects to make f.a. available

Question 43

Leptins role in lactation

Answer 43

Produced by fat cells, as adipose accumulates, leptin increases Declines as energy is mobilized from adipose (during lactation)