Hypotonic solutions dilution

The combination of active drug, preservative, and vehicle usually results in a hypotonic formulation (< 290 mOsm). Simple or complex salts, buffering agents, or certain sugars are often added to adjust osmolarity of the solution to the desired value. An osmolarity of 290 mOsm is equivalent to 0.9% saline, and this is the value sought for most ophthalmic and intravenous medications.The ocular tear film has a wide tolerance for variation in osmotic pressure. However, increasing tonicity above that of the tears causes immediate dilution by osmotic water movement from the eyelids and eye. Hypotonic solutions are sometimes used to treat dry eye conditions and to reduce tear osmolarity from abnormally high values. 

A cell placed in a solution more concentrated than itself (a hypertonic solution) will shrink due to loss of water, and may die of dehydration. A familiar example is a carrot placed in salty water. Within a few hours the carrot will become limp and soft because its cells have shrivelled. A cell placed in a solution more dilute than itself (a hypotonic solution) will expand as water enters it. Under such conditions the cell may burst. 

Erythrocytes contain 32 to 55% hemoglobin, about 60% water, and the rest as siroma. Stroma can be obtained, after hemolysis of the corpuscles by dilution, through the process of centrifuging and consists of lecithin, cholesterol, inorganic salts, and a protein, siromalin. Hemoly.sis of the corpuscles. or "laking" as i( is sometimes culled, may be brought about by hypotonic solution, by fat solvents, by bile... 

Osmotic effects are very important from a physiological standpoint. This is because biological membranes including the membrane of red blood cells behave like semipermeable membranes. Consequently, when red blood cells are immersed in a hypertonic solution (e.g., D5 A NS or D5NS), they shrink as water leaves the blood cells in an attempt to dilute and establish a concentration equilibrium across the blood cell membrane. Thus, when hypertonic solutions are administered into the blood stream, the fluid moves from interstitial and cellular space into the intravascular space. Conversely, when cells are placed in hypotonic environment (e.g., V2 NS), they swell because of the entry of fluid from the intravascular compartment, and may eventually undergo lysis. 

For potassium depletion, cells are washed with potassium-free buffer (140 mM NaCl, 20 mM 4-(2-hydroxyethyl)-l-piperazineethanesulfonic acid (HEPES), ImM CaCh, Img/mL o-glucose, pH 7.4) and then rinsed in hypotonic buffer (potassium-free buffer 1 1 diluted with distilled water) for five minutes. Then, cells are quickly washed three times in potassium-free buffer followed by incubation for 20 minutes at 37°C in buffer. Control experiments are performed in the same manner, except all solutions additionally contain 10 mM KCl. 

Tube Volume of Hypotonic Buffer (ml) Volume of 1 mg/ml Lysozyme Solution (jrl) Volume of Diluted Membrane Solution (/oil)... 

Like boiling-point elevation and freezing-point depression, osmotic pressure is directly proportional to the concentration of solution. This is what we would expect, because all colligative properties depend only on the number of solute particles in solution. If two solutions are of equal concentration and, hence, have the same osmotic pressure, they are said to be isotonic. If two solutions are of unequal osmotic pressures, the more concentrated solution is said to be hypertonic and the more dilute solution is described as hypotonic (Figure 12.14). 

If two solutions of identical osmotic pressure are separated by a semipermeable membrane, no osmosis will occur. The two solutions are isotonic with respect to each other. If one solution is of lower osmotic pressure, it is hypotonic with respect to the more concentrated solution. The more concentrated solution is hypertonic with respect to the dilute solution. 

Hypovolemic hypotonic hyponatremia— fluid and solute loss, with more sodium than water lost so that the remaining body fluid is hypotonic (dilute). May occur in hemorrhage or loss of vascular volume owing to gastrointestinal or renal loss (particularly owing to diuretic use). 

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