Vephy M4 Part 1 Flashcards
1
Q
Identify the major hormonal regulator of the reabsorption of phosphate
A
PTH
2
Q
Mode of action of PTH to phosphte
A
Decreases the rate of tubular reabsorption and increases the renal excretion of phosphate
3
Q
Other hormones
which inhibit Na/Pi cotransport
A
- Calcitonin
- Atrial natriuretic peptide
- Epidermal growth factor
- Transforming growth factors α and β
- Parathyroid hormone-related protein
4
Q
Other hormones
which stimulate Na/Pi cotransport by renal epithelial cells
A
- insulin
- growth hormone,
- insulin-like growth factor-1
5
Q
rate of reabsorption of renal phosphate is dependent of?
A
availability of Na+
6
Q
rate of reabsorption of renal phosphate is regulated by?
A
need of the animal for phosphate
7
Q
Renal excretion of phosphate is regulated by?
A
- glomerular filtration rate
- maximal rate of tubular reabsorption
8
Q
Which diet increase saliva production and the total salivary secretion of phosphate
A
high fiber
9
Q
What are the effects of increased endogenous salivary secretion of phosphate?
A
- increased intestinal absorption
- increased fecal losses and results in the net loss of phosphate
10
Q
Ruminants with this kind of diet use this
endogenous fecal loss of phosphate as the principal mechanism to regulate phosphate excretion
A
roughage diet
11
Q
ruminants given with this feed excrete more phosphate in the urine
A
concentrated diet
12
Q
Identify the important determinants of phosphate excretion in
ruminants
A
- quantity of saliva
- regulation of the phosphate concentration in saliva
13
Q
buffer volatile fatty acids and are nutrients for microorganisms in the rumen
A
Phosphate anions
14
Q
Parotid saliva in these species contains phosphate at levels of 16-40 mmol/L
A
ruminants
15
Q
An enzyme present in ruminants in which release the phosphate from the sugar moiety
A
Phytase
16
Q
Give two nutrients in the diet that antagonize phosphate absorption
A
aluminum & magnesium
17
Q
Diets with high content of these two substances raise the requirement for phosphorus
A
calcium & fat
18
Q
Approximately 60-70% of dietary phosphate is absorbed from the intestine by?
A
- active transport (Na/phosphate
cotransporter) - passive diffusion
19
Q
In ruminants, instead of sodium, the Na/phosphate
cotransporter is coupled with?
A
H+
20
Q
essential mineral component of the skeleton and plays a central role in maintaining the homeostasis of vertebrate animals
A
calcium
21
Q
involved in a wide variety of physiological processes
including muscular contraction, blood coagulation, enzyme activity, neural excitability, hormone secretion,
and cell adhesion
A
ionized calcium
22
Q
Endocrine factors that influence levels of calcium in the body
A
(i) parathyroid hormone
(ii) calcitonin
(iii) calcitriol
23
Q
bioactive vitamin D
metabolite derived from cholecalciferol (vitamin D3)
A
calcitriol (1,25-dihydroxycholecalciferol; 1,25-dihydroxyvitamin D)
24
Q
Calcitonin secreted by the which tissues of the thyroid gland
A
parafollicular or C-cells
25
synthesized and released by the chief cells of the parathyroid glands
PTH
26
Disruption of the normal regulation of calcium balance in animal results to?
hypercalcemia or hypocalcemia
27
What are the pathological effects associated with abnormal levels of calcium in the body?
1. calcification of vital organs & soft tissue
2. rickets
3. osteoporosis
4. reproductive disorders (puerperal tetany, milk fever)
28
99% of the calcium of the body is present in the inorganic matrix of bone as
hydroxyapatite
29
Aside from the hydroxyapatite, where are most of the remaining calcium sequestered?
plasma membrane and endoplasmic reticulum of cells
30
biologically active form of calcium
Ionized form (Ca2+)
31
these species limit and regulate Ca2+ absorption from the intestinal tract, skin, or gills
fishes
32
hormones that reduce the concentration of Ca2+ in the serum
calcitonin and stanniocalcin
33
Fishes primary role of reducing the loss of body Ca2+ and maintaining serum Ca2+
lack of parathyroid glands
34
Identify the important regulators of total body calcium in terrestrial vertebrates
parathyroid glands and the kidneys
35
Give the two primary functions of calcium
1. structural integrity of bones and teeth
2. as a messenger or regulatory ion
36
Influx of Ca2+ into cells can: (2)
1. regulate cellular function by interactions with intracellular calcium-binding proteins (e.g., calmodulin) and
calcium-sensitive protein kinases
2. stimulate biologic responses such as neurotransmitter release, contraction, and secretion
37
Present in cell membrane of chief cells of parathyroid glands and renal epithelial cells that regulate cellular functions once combined with Ca2+
G-protein-linked Ca2+-sensing receptor
38
Identify the 3 forms of extracellular and serum calcium
1.) ionized
2.) complexed to anions such as citrate, bicarbonate, phosphate, or lactate (5% of total calcium)
3.) protein-bound
39
which form of calcium dependent on the pH of the serum and is principally bound to negatively- charged sites on albumin
protein-bound
40
compose the ultra-filterable fraction of Ca2+ and represent the fraction
that is present in the glomerular filtrate
ionized and complexed Ca2+
41
What is the concentration of ionized Ca2+ in the serum in most domestic animals?
1.25-1.6 mmol/L (5.0 – 6.4 mg/dl)
42
Form of calcium that enters the glomerular filtrate and reabsorbed by the renal tubules
Ionized and complexed calcium
43
What are the factors by which kidney s reabsorb approximately 40-fold more calcium than is absorbed by the intestinal tract ?
1. high degree of blood flow
2. ultrafiltration in the glomerulus
44
Which part of the nephron 70% of filtered calcium is reabsorbed
proximal convoluted tubules
45
Part of nephron that absorbs about 20% of the filtered calcium
thick ascending loop of Henle
46
10% of the calcium is reabsorbed by which part of the nephron
distal convoluted tubule
47
Give the principal stimulator of calcium reabsorption in the distal
convoluted tubules
PTH
48
Reabsorption of calcium in the distal convoluted tubule is an active transcellular process and requires what?
calcium channels
49
an intracellular calcium-binding proteins
calbindins
50
Give the 3 measurements of calcium excretion in animals
1. calcium and calcium-creatine (Ca/Cr) ratio in the urine
2. fractional calcium excretion
3. 24-hour calcium excretion
51
Name the species that excrete larger amounts of calcium in the urine
Horses
52
a better indicator of calcium excretion because it corrects for errors in
timing of urine collections, concentration or dilution
Ca/Cr ratio of the urine
53
best measured in a fasting animal to eliminate the role of dietary
calcium on renal calcium excretion
Fractional calcium excretion
54
Identify the major sources of urinary calcium when there is little gastrointestinal absorption of calcium
1. calcium released from bone
2. obligate renal calcium loss
55
good measurement of daily calcium loss and may be used to
investigate calcium balance
24-hour calcium excretion
56
2 components of calcium absorption from the intestinal tract
(a) saturable or transcellular transport
(b) non-saturable or intercellular (paracellular) transport
57
associated with absorption rates of up to 95% of intestinal absorption of calcium
Low-calcium diets
58
high-calcium diets have absorption rates of about _____
40%
59
percentage of intestinal absorption of calcium is proportional to ___?
dietary intake
60
Diets deficient in calcium are associated with normal serum calcium concentrations due to compensation by? (3)
(i) bone resorption stimulated by parathyroid hormone
(ii) renal calcium reabsorption
(iii) increased synthesis of 1,25-dihydroxyvitamin D
61
Saturable transport is dependent of?
Vitamin D
62
Where does saturable transport occurs predominantly
duodenum, less on cecum and colon
63
1,25-dihydroxyvitamin D in the intestinal epithelial cell increases the expression of these calcium binding protein
calbindin
64
What stimulates transcellular transport of Ca2+?
vitamin D (1, 25-dihydroxyvitamin D)
65
occurs throughout the small intestine and is the main mechanism for calcium absorption in animals deficient in vitamin D
non-saturable calcium transport
66
Non-saturable Ca2+ transport is
dependent on the?
luminal Ca2+
67
Factors which increase intestinal calcium absorption, directly or indirectly, due to stimulation of 1,25-
dihydroxyvitamin D synthesis, include:
1. parathyroid hormone
2. growth hormone
3. testosterone
4. estrogen
5. furosemide
68
Factors that reduce intestinal absorption of calcium
1. Glucocorticoids
2. thyroid hormones
3. chronic acidosis
4. luminal conditions that induce the complexation of Ca2+
69
Two sources of Ca2+ in bone that can enter the circulation
1. readily mobilizable calcium salts in the ECF
2. hydroxyapatite crystals that require digestion by osteoclasts
70
source of calcium in bones that is present in small amounts, it plays a role of fine regulation of serum calcium
Mobilizable calcium ion
71
An animal with significant need for calcium from bone, must come from?
osteoclastic resorption of hydroxyapatite crystals
72
In ______ _______, stable balance between calcium deposition associated with bone formation and calcium release
adult animals
73
In ______ _______, bone has a positive calcium balance due to the relative excess of bone formation
young animals
74
Conditions associated with bone resorption and the release of calcium from bone which contributes to the development of hypercalcemia
1. Humoral hypercalcemia of malignancy
2. osteolytic bone metastasis
3. primary hyperparathyroidism
75
responsible for sensing serum Ca2+ concentration
Ca2+ receptor
76
90% of phosphate in the mammalian body is present as
hydroxyapatite
77
How many % of phosphate is present in soft tissues
10%
78
major intracellular anion existing in inorganic form
phosphate
79
Phosphate plays an integral role in metabolic processes such as (4)
1. energy metabolism
2. delivery of O2 to tissues
3. muscle contraction
4. skeletal integrity
80
What is the major regulators of the phosphate concentration in the serum, in nonruminant animals?
kidneys
81
80% of inorganic phosphate in the serum is in what form
dibasic form (HPO4)
82
20% of inorganic phosphate in the serum is in what form
monobasic form (H2PO4)
83
range of Serum Pi in adult animals
2.5-6.0 mg/dl (0.8-1.9 mmol/L)
84
unrealiable indicator of body stores and may be higher in growing animals than in adults
serum phosphate
85
In these species, external
parathyroid gland is located a considerable distance and cranial to
the thyroid gland
cattle & sheep
86
secrete and release parathyroid hormone
chief cells
87
Shape of inactive chief cells
cuboidal
88
do not have an active function in the biosynthesis of parathyroid hormone
oxyphils
89
increase in numbers in humans in response to long-term stimulation of
the parathyroid glands
oxyphil cells & transitional cells
90
Active PTH is packed by which cell organelles
Golgi apparatus
91
Identify the phases wherein concentration of calcium exerts an effect on chief cells
secreting and involuting phases
92
speed up the rate of secretion and shorten the resting phase of PTH
Low levels of intra- and extracellular calcium
93
suppress the rate of PTH secretion and lengthens the resting phase of the
secretory cycle
high intra- and extracellular levels of calcium
94
these species have consistently more PTH secretory granules than man and other animals
bovine parathyroid cells
95
The correct term for release of insulin from secretory granules in the cells of the pancreatic islet
emiocytosis
96
Why do parathyroid glands have a unique mechanism for feedback
control?
due to the cellular response to the concentration of calcium and to a lesser extent of magnesium ion
97
What is the influence of serum levels of ionized calcium and interaction with the Ca2+-sensing receptors on chief cells?
formation of an inverse sigmoidal-type of relationship between serum Ca2+ and PTH concentrations
98
What are the major inhibitors of PTH synthesis and secretion?
1. increased serum levels of Ca2+
2. 1, 25-dihydroxyvitamin D.
99
What happens if there is elevation of blood calcium by IV infusion?
There is rapid and pronounced reduction in circulating levels of immunoreactive parathyroid hormone.
100
What is likely to happen if the blood
calcium is lowered by infusion of EDTA?
brisk and substantial increase in the level of immunoreactive PTH
101
True or False. Concentration of blood phosphate direct regulatory influence on the synthesis and secretion of PTH.
False. Because it has no direct regulatory influence on the synthesis and secretion of PTH
102
An elevated blood phosphorus level may lead indirectly to parathyroid stimulation, and this is due to?
High levels of phosphorus can lower calcium levels in the body.
103
This ion has an effect on secretory
rate of parathyroid hormone similar to that of calcium, but the effect is not equipotent to that of calcium.
Magnesium [Mg2+]
104
Why does Magnesium ion has reduced potency than Ca2+ in terms of PTH stimulation?
Because magnesium ion has reduced binding affinity for the Ca2+
-sensing membrane receptors on chief cells.
105
True or False. Calcium ion only controls the rate of biosynthesis and secretion of parathyroid hormone, while magnesium control the other metabolic and intracellular degradative processes occur within chief cells.
False. Biosynthesis, secretion of PTH and other metabolic processes of chief cells are controlled by Calcium.
106
It is the principal hormone involved in the minute-to-minute, fine regulation of blood calcium in mammals
PTH
107
Give at least five most important biologic effects of PTH
1. elevate the blood concentration of calcium.
2. decrease the blood concentration of phosphorus.
3. increase the urinary excretion of phosphorus by a decreased rate
of tubular reabsorption.
4. increase the tubular reabsorption of calcium.
5. increase the rate of skeletal remodeling and the net rate of bone
reabsorption.
108
facilitates the movement of calcium from bone to the extracellular fluid for the fine adjustment of the calcium concentration in the blood
Osteocyte-osteoblast “pump”
109
primarily responsible for the long-term
actions of PTH on increasing bone resorption and overall bone remodeling
Osteoclasts
110
a complex, multistep, process that involves the activation of multiple genes and the action of multiple hormones
bone resorption
111
a membrane-bound protein on osteoblasts that serves as a common mediator for osteoclastic bone resorption
RANK ligand or RANKL (Receptor Activator of Nuclear factor-kappa B Ligand)
112
RANK ligand or RANKL was initially called as?
osteoclast differentiation factor or osteoprotegerin ligand
113
novel member of the TNF receptor superfamily that is produced by cells of the osteoblast lineage and is a negative regulator of bone resorption
osteoprotegerin / decoy receptor
114
True or False. When soluble
osteoprotegerin binds to the RANK receptor, it prevents the RANK ligand from binding and activating the receptor.
True.
115
leads to osteopetrosis associated with decreased osteoclast formation and function
Overexpression of osteoprotegerin (OPG)
116
alterations in this ratio may
be a major cause of bone loss in metabolic disorders such as estrogen-deficiency or glucocorticoid- excess
RANKL; OPG
117
an organic component phagocytized
by osteoclasts and transported across the cell and released into the ECF
hydroxyproline
118
site of action of PTH on the tubular reabsorption of phosphate has been localized to this region
PCT
119
True or False. PTH leads to the increased urinary excretion of potassium, sodium, bicarbonate, Camp, and amino acids
True.
120
True or False. Capacity of PTH to enhance the renal reabsorption of calcium is of considerably more important than its effect phosphaturia.
True. Renal reabsorption of calcium is of considerably more important in the maintenance of calcium homeostasis
121
True or False. Urinary excretion of magnesium and ammonia, and the titratable acidity of the urine are increased by PTH.
False. It is decreased by PTH.
122
promotes the absorption of calcium from the gastrointestinal tract in animals
PTH
123
The major organ for the degradation of PTH
kidney
124
PTH half life
less than 5 mins
125
PTH is removed from the circulation by?
endopeptidases in hepatic Kupffer cells
126
plays a central role in the pathogenesis of humoral hypercalcemia of malignancy
Parathyroid hormone-related protein (PTHrP)
127
True or False. PTHrP is not strictly a calcium-regulating hormone.
True.
128
Function of PTHrP is likely as an _________ regulatory factor
autocrine or paracrine
129
play a role in stimulating the transport of calcium by alveolar epithelial cells from serum to milk
PTHrP
130
