Comparative Vertebrate Physiology
HUMAN - Renal Physiology - Sodium Infusion
The purpose of today's simulation session is to allow you to investigate the
responses of renal hormones and the mammalian kidney to changes in plasma
osmolarity.
The hormone aldosterone stimulates sodium reabsorption mechanisms in
the distal convoluted tubule to allow for the conservation of sodium. You should
review the sequence of steps and hormonal events (see lecture notes) which lead
to the release of aldosterone.
As osmotic regulation usually involves coordinated salt and water moving
maneuvers, in times of water deprivation (or other disturbances which may cause
hyperosmolarity of the plasma) increased levels of antidiuretic hormone (ADH)
are also released. ADH stimulates collecting duct water reabsorption which
results in the formation of a more concentrated urine.
Today you will investigate the roles of these hormones in the body's
response to infused loads of various osmolarities. The HUMAN model allows you
to infuse fluid directly into the blood stream of the subject (i.e. it simulates an
intra-venous infusion). You will vary the osmolarity of the infusate by altering its
NaCl content selecting several concentrations of the infusion fluid: one isotonic
with plasma, several that are hypertonic (up to twice normal Na concentration)
and a few hypotonic fluids.
The variables that should be monitored include*:
Plasma renin activity
Plasma aldosterone concentration
Excretion of sodium in the urine
Plasma antidiuretic hormone concentration
Urine osmolarity
To conduct an infusion experiment you must set all of the following*:
1) the concentration of the infusion
2) the time span (duration) of the infusion
3) the total infusion volume
Note: the units of volume are Liters, not ml, as indicated in the output
[Note: a small infusion of 250 ml. can be accomplished in 30 min. It would take
approximately 1 hour to infuse a liter.]
Of course as you repeat the experiment with a new subject each time, you
should change only one parameter, i.e. the Na concentration of the infusion fluid,
and keep all others constant. (Check with the instructor as to which set of HUMAN tables is most
appropriate to avoid resetting tables each time.- try experiment 18)
It is convenient to record the values of the variables at a set time of one
hour after the beginning of the infusion. Keep this time consistent for each run of
the experiment.
The experiment
In this simulation YOU are responsible for setting up the experiment on
your own. Follow the guidelines above carefully. Find the names for the variables
you wish to track and the parameters you wish to change by consulting your
human variables and parameter lists and then plan out and run the experiments.
* To locate the HUMAN code names for the Table and Parameter items listed above, use your
browser's Find...(in page) function to search the on-line HUMAN variables list (see HUMAN Infusion
Checkup below for 'practice')
The Lab Analysis/Write-up (Full style) or see modified instructions for 'short' write-up
Give some background introduction information on the functions of
aldosterone and ADH in the control of kidney function and plasma osmolarity.
Include at least one reference (the text is acceptable). Your introduction should
predict, in general terms, the responses to the various infusions.
up.
It is not necessary (or sensible) to do a Methods section in a HUMAN write-
Your Results section should include a graph (or series of graphs) that
illustrate one set of relationships between the hormones and the renal functions
that they control (e.g. you may line up two or more curves on a page so that the
reader can see a parallel or inverse relationship). As always, include a narrative
part to the results section which describes the patterns seen in the data.
Your discussion explicates how your data illustrate the function of a/the
renal hormone(s) in regulating plasma osmolarity.
* Short
-
form report
do only the results and an abbreviated discussion section
no more than 2 pages of plots ( 1 is preferred)
no more than one page of typed text in your analysis.
Comparative Vertebrate Physiology
HUMAN Infusion Checkup
I. Run the model under normal conditions for 15 min. and fill in the value for
each of the following variables and parameters:(purpose: can you find needed variable names)
Description
____________
[aldosterone] plasma
[ADH] in plasma
[potassium] in urine
[sodium] in infusate
volume of an infusion
HUMAN name
____________
____________
____________
____________
____________
____________
Value
________
________
________
________
________
________
Units
_______
_______
_______
_______
_______
_______
II. In a newly initialized subject, infuse one liter for a one hour period a solution
having one half the normal Na concentration. Fill in the values below. (purpose: Can
you successfully carry out an infusion)
Time
______
Plasma [Na]
__________
Urine [Na]
__________
Urine [Osm]
__________
Plasma[Osm]
__________
Start
__________
__________
__________
__________
30 min.
__________
__________
__________
__________
60 min.
__________
__________
__________
__________