What is Osmolality?

This site is presented by Advanced Instruments, Inc

Papers and Publications Osmo for beginners Clinical Uses History
Definitions Related Links Frequently Asked Questions

Frequency Asked Questions
Following are frequently asked questions regarding the use of osmolality in the pharmaceutical, biotechnology, and sports medicine applications.


1. What is tonicity?
a. The normal state of slight contraction, or readiness to contract, of healthy muscle fibers.
b. The effective osmotic pressure of a solution.
In pharmaceutical parenteral drug solutions tonicity can be adjusted in hypotonic solutions by adding dextrose or sodium chloride.

2. Why is this important for pharmaceutical manufacturers?

Pharmaceutical solutions that are meant for application to delicate membranes of the body should be adjusted to approximately the same tonicity as that of the body fluids.

3. What does isotonic mean?
Isotonic solutions cause no swelling or contraction of the tissues with which they come in contact, and produce no discomfort when instilled in the eye, nasal tract, or other body tissues.

4. What does hypotonic mean?
The tonicity of the solution is less than that of the cells. When this occurs, water enters into the blood cells causing them to swell and finally burst, with the liberation of hemoglobin, or water invasion of the body’s cells. If this invasion is beyond the body’s cells, then water intoxication results, with convulsions and edema.

5. What does hypertonic mean?
The tonicity of the solution is greater than that of the cells, which can cause a variety of complications, such as, hyperglycemia, intracellular dehydration, loss of water and electrolytes, dehydration and coma.

6. What is crenation?
The water within the cell membrane attempts to dilute the surrounding salt solution until the salt concentrations on both sides of the erythrocyte membrane are identical. This outward passage of water causes the cells to shrink and become wrinkled or crenated. The salt solution in this instance is said to be hypertonic with respect to the blood contents.

The red blood cell (R.B.C.) is not impermeable to all drugs, i.e., it is not a perfect semipermeable membrane. Thus, it will permit the passage of not only water molecules, but also solutes such as UREA, ammonium chloride, alcohol, and boric acid. The molecules of these compounds can cross the R.B.C. and cause hemolysis at any concentration. The mucous lining of the eye acts as a true semipermeable membrane to boric acid in solution. Hence, boric acid can be used for ophthalmic solution to adjust tonicity.

7. When eating foods with high osmolality due to high electrolytes, amino acids and simple sugars, why do people suffer discomfort?
When nutrition of high osmoticity is ingested, large amounts of water will transfer to the stomach and intestines. Large amounts of water in the gastrointestinal tract can cause distention, cramps, nausea, vomiting, and shock.

The body tries to keep the osmoticity of the contents of the stomach and intestines at approximately the same level as that of the fluid surrounding them. There is great variation from one individual to another in sensitivity to the osmoticity of foods.



1. Why are some cell culture media better than others?
Media originally used for growth of mammalian cells were based on biological fluids, such as plasma. This type of media suffered many disadvantages including batch variation and vulnerability to contamination.

2. What other media is more robust?
Reduction in the number of components in media design is essential for cell growth. Eagle’s basal media (BME) and Eagle’s minimum essential medium have found wide-ranging uses and are both available commercially.

3. What is media composed of?
Formulations include a complex mixture of salts, carbohydrates, amino acids, vitamins, hormones, and growth factors. The salt concentration needs to be isotonic to prevent osmotic imbalances.

4. What should the osmolality be for growth media?
The osmolality of standard cell growth media for mammalian cells is 300mOsm/kg, an optimal value for most cell lines.

5. How can cell culture media be made?
One of the most common methods used today is by utilizing a bioreactor.

A bioreactor allows the growth of human tissues outside of the body that amass and behave like those in the body.

Another is the Rotary Cell Culture System, as it provides a gentler environment than a dynamic or static tissue culture system, thereby allowing cells to aggregate, grow 3-dimensionally, and differentiate. The result will be cells or tissues that closely resemble the in vivo tissue equivalent.



Sports Medicine
Hydration and Dehydration FAQs

1. What is the definition of dehydration?
The lack of adequate body fluids needed for the body to carry on normal functions at an optimal level. Dehydration can be caused by fluid loss (through vomiting, diarrhea or excessive urination), inadequate intake, or a combination of both. The most common cause of dehydration in infants and children is acute gastroenteritis with its associated vomiting and diarrhea.

Dehydration is classified as mild, moderate, or severe based on the percentage of body weight lost during the acute illness. Depending on age, mild dehydration is seen with a loss of 3-5% of body weight. Moderate dehydration is seen with a 6-10% loss of body weight. Severe dehydration, which is a life-threatening emergency, occurs when more than 9-15% of body weight is lost.

2. What causes dehydration during exercise?
Causes of dehydration include excessive fluid losses due to excessive sweating, inadequate fluid intake, or a combination of these factors.

3. What are signs of dehydration?

Dry lips
Slightly dry mouth membranes

Very dry mouth membranes
Sunken eyes
Sunken fontanelle (soft spot) on infant’s head
Skin doesn’t bounce back quickly when lightly pinched and released

All signs of moderate dehydration
Rapid, weak pulse (more than 100 at rest)
Cold hands and feet
Rapid breathing
Blue lips
Confusion, lethargy, difficult to arouse

4. How should lost fluids be replaced?
In cases where losses aren’t severe, athletes can replace these fluids by drinking isoosmotic beverages that will serve to replace lost nutrients and electrolytes.

In severe cases of dehydration, athletes are put on IV lines on-site or in a hospital.

5. Why are sports beverages popular?
When a workout period exceeds 60 minutes, sports drinks can be beneficial because they provide a source of fuel for working muscles and will speed the absorption of water and glucose (sugar) from the small intestine. Sports beverages are recommended for activities lasting longer than one hour. (Drink plain water before or during activities lasting 60 minutes or less). With sports drinks, continued exercise won't deplete muscle glycogen as fast and performance time may be lengthened. Sports drinks can also help reduce recovery time by rapidly restoring muscle glycogen after exercise. Sports drinks are also beneficial when exercising in high heat or humidity, the electrolytes help to enhance fluid absorption.

6. When should sports beverages be used?
Sports drinks are helpful before, during and after exercise. Sports beverages are scientifically formulated to help restore the essential fluids, energy, and minerals your body loses during exercise. The carbohydrate concentration and sodium combination in a sports drink assures rapid hydration and improved performance.

7. How should sports beverages be used?
Recommendations when taking a sports beverage:
The quality of carbohydrate needed to improve performance can easily be met by consuming a sports beverage under the following recommendations:

Before exercise:
• Drink 8 to 24 ounces of a sports beverage 2-4 hours before exercise or
• Drink at least 4 to 8 ounces of a sports beverage immediately before exercise
During exercise:
• Drink 4 to 8 ounces of a sports beverage every 15-20 minutes after the first 30 minutes of exercise
After exercise:
• Drink at least 8 to 16 oz of fluid after exercise. (drink 2 cups of fluid for every pound lost after exercise)
• Consume or drink 40-60 grams of carbohydrate ASAP or within the first 30 minutes after exercise, and at 2 hour intervals up to 4 hours after exercise

8. What is the difference between drinks for hydration, energy and recovery?
An energy drink contains a significant amount of carbohydrate; this is going to reduce the hydration benefits of that drink.
A hydration drink will not provide sufficient carbohydrate for times of glycogen depletion.
A recovery drink will not provide rapid energy absorption and hydration in the way that you would need during an event. The best recovery drinks actually encourage the release of insulin to stimulate maximum glycogen rebuilding - which can reduce the amount of energy that is available in the blood short term.

9. What problems can exist with sports beverages?
Slow to empty from the stomach
If a drink has a high % by volume of carbohydrate it will not empty rapidly. This will be uncomfortable and will pull fluid back into the stomach. So it will further dehydrate you. It will not give you quick benefits of the energy it contains.

Gastro-Intestinal Problems
If a drink contains too much fructose it will be hard for the stomach to digest and absorb it. Acid levels may also be high and can cause GI problems. Acid is used in all non-alcoholic beverages primarily for taste and product stability, and it has the same function in sports drinks - but too high an acid level can be hard to absorb and can cause GI problems. Other gastro-intestinal problems would most likely come from taking the wrong drink at the wrong time.

Hypoglycemia is a condition when the blood glucose levels are at seriously low levels, taking away the body's energy - it's a medical term for bonking or hitting the wall.

Hypoglycemia is one of the largest problems with many sports drinks. Unless a drink is taken actually during continuous prolonged exercise, when the insulin response to exercise is somewhat reduced, sports drinks formulated with glucose or sugars that break down to glucose will cause an insulin reaction - because the body will at all times attempt to maintain homeostasis, this means (constant state of balance)

The insulin release will reduce blood sugar levels and could cause hypoglycemia if blood sugar dips too low - lowering the amount of blood sugar available for fueling performance. Insulin is in effect a storage hormone for glucose. Its job is to prevent high levels of blood sugar by removing excess glucose from the blood and promoting its storage as fat or glycogen. This is how a high carbohydrate diet can lead to obesity. The control of insulin production is very important.

With little or no insulin we have a condition known as Diabetes (persistent high blood sugar levels). This leads to complications in many tissues and needs treatment. With too much insulin secretion, or if insulin is too effective, too much glucose is removed too fast from the circulation, and hypoglycemia results.

10. Is it possible to drink too much?
Yes. While most runners and cyclists know the importance of hydrating, some don't realize over-hydrating can dangerously lower blood sodium levels-a condition known as hyponatremia.

Hyponatremia seems most common in female and beginning marathoners and triathletes for two reasons. One, they are on the race course for many hours, losing lots of sodium in sweat. Two, they are hypervigilant about staying hydrated. "They drink lots of water in the days before the race, then stop at every fluid station along the course," he says.

In a hot marathon or triathlon, if you drink too little, you can dehydrate and risk early fatigue and heat illness. But if you drink too much, you risk low sodium.

11. How can hyponatremia be avoided?
Keys to avoiding hyponatremia are 1) don't drink more than you sweat; and 2) favor sports drinks, which have some sodium, over water, which has none. Also, focus on a salty diet in the days before the race and eat some pretzels in the last half of the race.

Baumagarten, Bloebaum, Ross, et al. " Normal Human Synovial Fluid: Osmolality and Exercise - Induced Changes" The Journal of Bone and Joint Surgery, Decmeber 1985, V 67-A No. 9 pp 1336-1339
Link: www.gatorade.com