In article <3858BEBC.1EDD at erols.com>, Stuart Dunn <dunns99 at erols.com> wrote:
> > 2) Calcium levels have nothing to do with pH of the urine.
> They do effect the pH level of urine. The breakdown of protein produces
> acids which are then excreted through the urine. Since the pH level of
> urine must be maintained, the body excretes more calcium in the urine.
> Cysteine and Methionine are the amino acids that increase calcium loss
> when consumed to excess, and most people get lots of these two amino
> acids from nonvegan foods. I did find some interesting information on
> protein, and I'll post it sometime today.
1)Proteins are not broken down in the kidney. Digestion involves
adsorbtion of substances through the gut. The liver is the main player in
the disemination of nutrients to the rest of the body. The kidney job is
to maitain a proper electrolitic balence in the plasma. The liver is
responsible for the ecretion of proteins, amino acids, bilirubin and
others thruogh the bile which is dumped into your lower intestine.
If proteins or amino acids appear in significant quatities (detectable
quatities by colormetric tests: sensitivity ~ .1uM) in the urine then that
is gernerally considered to be evidence of glomerular damage. The
exception is peaple that have just finished heavy extended
exerciseimmediately preceeding the urine sample..
2) calcium is readsorbed by in the distal tubules. The rate of
readsorbtion is dependant on the plasma levels of calcium. The main
player here is a hormone called PTH. As PTH levels increase the amount of
calcium that is activly readsorbed by the distal tubules increses and the
calcium levels in the plasma increase. Once again, I emphasize the fact
that if the body needs to conserve calcium, it will. The PTH also
increases the amount of calcium that is readsorbed in the gut which is
most significant. PTH will inhibit the readadsorption of phosphate in the
proximal tubules. The net effect of this action is for the plasma calcium
NOT to precipitate in the tissue in the form of calium phosphate. PTH
also inhibits the readsorption of Bicarbonate and sodium. This allows
for the prevention metabolic alkalosis which could result from the
release of Bicarbonate when the hydroxyapetite is disolved in the bone.
BTW, normal urine has a pH range of 5-7. That is a 100 fold difference in
HDROGEN ION CONCENTRTION from high to low. This dimonstrates that pH is
not all that tightly regulated as you seem to make it out to be
Peter Pediaditakis
Dept. of Pathology
University of Pittsburgh
