Class Notes (836,677)
Canada (509,870)
UOIT (1,700)
Biology (294)
BIOL 1840U (44)

Mineral Metabolism I

3 Pages
Unlock Document

BIOL 1840U
Peter Cheung

Mineral Metabolism I. Calcium Balance a. Fast facts i. Total body store—1000 gm (1kg) ii. Ingested daily—1 gm/day iii. Net uptake—200 mg / day iv. Net excretion—200 mg/day b. Body can function on less than the recommended daily dose of Ca, but that requires energy to extract it more fully and reabsorb it (using PTH & vitamin D action) c. Recommended Ca Intake i. High for teens ii. ~1000 mg for adults iii. 1500 mg for post-menopausal women b/c intestine is less efficient at absorption d. Serum Levels i. Total [Ca] = 10 mg/dl = 2.5 mM 1. ½ total [Ca] is ionized & remainder is bound to albumin or globulin ***Labs measure total [Ca] but hormones only sense ionized Ca e. Calcium Balance i. Ca + PO4 (serum) ⇔CaPO4 (serum) ⇔CaPO4 (bone) ii. Hormones shift this balance iii. Kidney makes the fastest changes b/c it filters blood very rapidly (180 L/day) II. Hormones regulating Ca balance a. Parathyroid Hormone (PTH) i. Function—rapidly increases ionize serum [Ca] in response to low [Ca] 1. ↑Ca + ↓PO4 (serum) ⇐CaPO4 (serum) ⇐CaPO4 (bone) 2. phosphate is lost from kidney (↓PO4) 3. CaPO4 in bone is mobilized (↑resorption) 4. ↑renal Ca reabsorption ii. Synthesis/ Storage/ Secretion 1. Chief cells of parathyroid gland synthesize PTH 2. 2 cleavages (1 in ER; 2 in Golgi) => active form 3. stored in secretory granules 4. metabolized in liver & kidneys 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 iv. Mechanism of Action 1. binds serpentine PTH receptor →GPCR →↑cAMP (can be measured in urine) v. Cellular Targets 1. Kidney a. Inhibits PO4 uptake in proximal tubule by removing transporter (NaPi II) at apical membrane i. This => ↑[Ca plasma] b/c less is complexed with PO4 b. Increases Ca reabsorption in CCD & DCT by hyperpolarizing apical mem. (=> nonselective cation/Ca channel opens more) 1 2. Bone—increases # osteoblasts => increased resorption of bone (turns on osteoclast H+ pumps) b. Calcitonin (CT) i. Function—rapidly lowers ionized plasma [Ca] 1. ↓Ca + PO4 (serum) ⇔CaPO4 (serum) ⇒CaPO4 (bone) 2. ↓renal Ca reabsorption 3. ↓osteoclast resorption ii. Formation/ Storage/ Secretion 1. produced by “C-cells” of thyroid (also by parathyroid & thymus) 2. gene consists of 6 exons generating 2 distinct splice mRNAs a. calcitonin precursor (CT) b. calcitonin gene-related peptide (CGRP)—fxn is vasodilation
More Less

Related notes for BIOL 1840U

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.