Increased glomerular filtration rate: increased glomerular capillary filtration coefficient

2021-04-30 09:43 PM

Although an increase in Kf leads to an increase in glomerular filtration rate and a decrease in Kf, and a decrease in glomerular filtration rate, the Kf change is almost certainly not the primary mechanism for normal daily adjustment of glomerular filtration rate.

Glomerular capillary filtration coefficient (Kf) depends on the permeability of glomerular capillaries and surface area. Kf is not directly measured, but may be based on the glomerular filtration rate division by sieve pressure:

Kf = GFR/Net filtration pressure

Since the total renal glomerular filtration rate is 125 ml/min and the sieve pressure is 10 mm Hg, the Kf is equal to 12.5 ml/min / mmHg. The Kf per 100 grams of kidney weight, averaging about 4.2 ml/min / m mmHg, is about 400 times that of other capillary systems in the body. The Kf of many body tissues averages only about 0.01 ml/min / mm Hg per 100 grams. This high Kf is consistent with the high filtration rate of glomerular capillaries.

Although an increase in Kf leads to an increase in glomerular filtration rate and a decrease in Kf, and a decrease in glomerular filtration rate, the Kf change is almost certainly not the primary mechanism for normal daily adjustment of glomerular filtration rate. In some diseases, Kf is low because of a decrease in the number of functional glomerular capillaries (reducing the filtration surface area) or decreasing the glomerular capillary membrane thickness (reducing permeability). For example, chronic diseases, such as uncontrolled hypertension and diabetes decrease Kf by decreased basal membrane thickness and even by the destruction of capillaries thereby causing loss of functional capillaries.

 

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