KIDNEYS

Some basics on acid/base balance

The kidneys maintain the bodies homeostasis by getting rid of the waste products in the body
Acid/base imbalances can be tested for in the urine of the patient. The pH of urine normally ranges between 5 and 6
The blood needs to be in a narrow range of pH between 7.35 and 7.45 (slightly basic)
When the pH diverges from this range, it becomes incompatible with life processes. Proteins will begin to be denatured and digested, the enzymes used in many reactions will lose the ability to function, and the body will no longer be able to sustain itself
The short-term regulation of the pH or acid-base balance of the body is compensated for by altering the rate of ventilation in the respiratory system. More detail will be gone into this under the respiratory tab.
The kidneys regulate the pH balance of the body in a much slower process by regulating the pH of the blood plasma. It can take the kidneys several hours to days in order to respond to the acidity in the body

The kidneys are responsible for reabsorbing bicarbonate from the urine and to expel hydrogen ions into the urine
Renal excretion is the major homeostatic control for maintaining a stable pH
Bicarbonate (HCO3-) does not have its own transporter; thus, reabsorption requires a set of reactions in the various regions of the kidney. These include the lumen and tubular epithelium.
- In order to maintain acid/base balance, the kidneys must reabsorb all filtered bicarbonate ions
When the body is in an acidic state, tubular cells will uptake more bicarbonate from the tubular fluid, more hydrogen cells will be secreted so that more bicarbonate will be generated, leading to the formation of more NH3 (ammonia) buffer
- The kidneys increase ammonia production and secretion in response to an increase in acidity
- Hydrogen ion secretion takes place in the collecting tubule and is important in the process of maximally acidifying urine. This must happen so that there is also adequate ammonia excretion.
When the body is in an alkalotic state, the kidneys will excrete more bicarbonate by decreasing the number of hydrogen ions that are secreted from the tubular ells. This will then lower the rates of glutamine metabolism and the excretion of ammonia and cause the pH to rise
Even though extracellular pH is the primary factor that goes into regulating net acid secretion, the circulating volume, aldosterone, and potassium concentrations can all affect acid excretion

A poor diet is the most significant reason that increases the incidence rate of renal failure
Raw fruits and vegetables are the best source of nutrients to help the body maintain a constant pH. When foods are cooked, a lot of the nutrients are destroyed due to the breakdown of proteins, causing them to become more acidic.
Plant based foods are the best alaklizing foods to consume
A diet high in protein can also cause a more acidic environment

Arterial Blood Gas (ABG) and Urine tests can be used to measure the pH of the body
Normal ABG values
- pH: 7.35-7.45
- pCO2: 35-45
- HCO3: 24 +/- 2
- pO2: 80-100
- Lactate: <1.9
Normal urine pH
- 5.0-6.0

“Dr. Jeffrey Morrison on restoring pH balance in the body. (Picture). Retrieved from http://www.morrisonhealth.com/blog/dr-morrison/balancing-act-health

Graham, T. (2006). “Physiology, Renal Acid Base Excretion: Acid Base Online Tutorial.”University of Connecticut. Retrieved from http://fitsweb.uchc.edu/student/selectives/TimurGraham/Renal_Acid_Excretion.html

Koeppen, B. (2009). The Kidney and acid-base regulation. Advances in Physiology Education. Vol. 33 no. 4, 275-281 DOI: 10.1152/advan.00054.2009

Nathwani, P. (December 26, 2015). Renal Tubular Acidosis (Power Point Slides). Retrieved from http://www.slideshare.net/ ParthNathwani/renal-tubular-acidosis-56453769

Pathway Medicine. (2010). “Acid Base Physiology.” Pathway Medicine. Retrived from http://www.pathwaymedicine.org/acid-base-physiology

This tab was created on October 16, 2016

Last edited on October 23, 2016