leen
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A 3-year-old boy has a mutation in the calcium receptors on cell surfaces of his parathyroid gland and on the basolateral (blood) side of the thick ascending limb of the loop of Henle. Which of the following patterns is expected with a mutation that leads to activation of this receptor in the absence of binding of its ligand, calcium?
Serum
Ca2+ Parathyroid hormone Urine calcium
A ) Hypercalcemia high high
B ) Hypercalcemia high low
C ) Hypercalcemia low high
D ) Hypercalcemia low low
E ) Hypocalcemia high high
F ) Hypocalcemia high low
G)hypocalcemic low high
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| robin082006
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B
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| star1
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G receptor stimulation causes the PTH to sense that there is high serum calcium so PTH will not be secreted ...........> Serum Ca will be low ............> Urine Ca will be High.
AM I RIGHT?
robbin plz explain ..........
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| Cedrick
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Correct reasoning star1
B
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| star1
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Cedrick so you agree with me but u have choose B . can u explain to me???
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| Cedrick
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I am sorry
I need to serach my question back and get to you
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| Cedrick
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Search
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| star1
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OK
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| robin082006
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I CHOOSE B BECAUSE I THINK ACTIVATION OF THE RECEPTOR LEADING TO INCREASED PTH.
Edited by robin082006 on 07/02/06 - 02:25 PM
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| Cedrick
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Parathyroid hormone is that controls calcium and phosphorus hemostasis,as well bone physiology
hypocalcemia will will activate calcium receptors in the parathyroid gland,PTH release
this will stimulate osteoclasts to break down bone and release calciumin to the blood
I don't know about the urine
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| study_ing
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G---star 1 u r right
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| tolito
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this is a case of PRY hyperthyroidism!!! so serum pth is high, serum calcium is hig and urine ca is low with low serum phosphate!!
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| tolito
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answer is B
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| study_ing
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how duz a cell producing PTH know when to stop secreting PTH?
BY SENSING CALCIUM
thanx to mutation, more ca enters the secreting cell even when plasma levels are NOT high..hence PTH release will be inhibited
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| study_ing
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PTH secretion falls with higher Ca levels..
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| study_ing
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ok i just searched on the net
http://www.bme.jhu.edu/~rcheong/Year1/organsystem...
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| muzammil
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sorry folks posted a wrong one before here is the answer is g
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| study_ing
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iii. [Ca] in serum controls release of PTH
1. Ca => parathyroid gland releases PTH in 3-5 minutes
2. sensed by Ca sensor: low Ca => sensor turns off => [Ca] IC & transcription of PTH
3. Ca => PTH transcription
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| muzammil
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satr 1 is very right here is the refrence and the link for details
"Understanding the role of the calcium sensor in calcium homeostasis has benefited greatly by the study of mutations in the human gene encoding this receptor:
Inactivating mutations: A large number of different mutations in the calcium sensor gene have been identified in patients affected by a type of calcium resistance known as familial hypocalciuric hypercalcemia. The different mutations result in a spectrum of calcium sensor dynfunctions, ranging from total inactivation to a moderate decrease in affinity of the receptor for calcium. A prominent clinical consequence of such mutations is an abnormal set point or sensitivity of the parathyroid gland to blood calcium concentration. Abnormalities in renal excretion of calcium are also observed.
Activating mutations: Certain types of mutations lead to a calcium sensor with an elevated sensitivity to calcium. The clinical consequence of such mutations is familial hypercalciuric hypocalcemia - basically the opposite of what is seen with inactivating mutations in the sensor gene. High blood calcium affects the normal calcium sensor to suppress parathyroid hormone secretion. If the calcium sensor is constitutively more active than, a type of hypoparathyroidism results. "
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| muzammil
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http://www.vivo.colostate.edu/hbooks/pathphys/end...
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| tolito
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Thanks for the great information. yes it is G.
these darn receptors!!!!
the ca receptor is a Gi receptor.
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| sridevibandaru24
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Its G
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