Fluid-Electrolyte & Renal

PCT has maximum capacity of reabsorption. Most of the reabsorption takes place here.

60% of TBW is fluid where 40% is ICF & 20 is ECF

Features of proximal acidification:
1. It is a high capcity system used for huge bicarbonate reabsorption mainly in PCT and partly in ALH (if HCO3- escape reabsorption in PCT).
2. Here secreted Ht from tubular cell is titrated in tubular fluid by filtered HCO3- for its reabsorption with no net loss of H+ from body and no net gain of HCO3- to blood. Merely proportional replacement of filtered HCO3- in blood occur by this mechanism.
3. Simply it helps to maintain the present bicarbonate status (alkali reserve) of body without urinary HCO3- loss. It does nothing to change the acid base status of body.
4. It does not create high luminal H+ concentration.
5. It creates a very low pH gradient by decreasing filtrate pH from 7.4 to 6.8.
6. It is important because it saves huge amount of HCO3- per day (about 4500 mmol) by preventing their urinary loss. Kidney cannot be in a position to excrete non volatile acid load without prior reabsorption of all filtered HCO3- because one HCO3- loss from the body is equivalent to one H+ gain to the body.

Thiazide diuretics have a unique effect on the distal tubule; they increase Ca2+ reabsorption, thereby decreasing Ca2+ excretion and clearance. Because parathyroid hormone (PTH) increases Ca2+ reabsorption, the lack of PTH will cause an increase in Ca2+ clearance. Furosemide inhibits Na+ reabsorption in the thick ascending limb, and extracellular fluid (ECF) volume expansion inhibits Na+ reabsorption in the proximal tubule. At these sites, Ca2+ reabsorption is linked to Na+ reabsorption, and Ca2+ clearance would be increased. Because Mg2+ competes with Ca2+ for reabsorption in the thick ascending limb, hypermagnesemia will cause increased Ca2+ clearance.

Aquaporin-1 is localized to both the basolateral and apical membrane of the proximal tubules and its presence allows water to move rapidly out of the tubule along the osmotic gradients set up by active transport of solutes, and isotonicity is maintained. 60-70% of filtered water is reabsorbed in PCT.

Glucose is completely reabsorbed by kidney unless any abnormality.

Explanation:

Total body water (TBW) is approximately 60% of body weight. Body water is inversely proportional to body fat. The percentage of TBW is highest in new-borns then in adult males and lowest in adult females and in adults with a large amount of adipose tissue.

Average
Range
Total plasma Calcium concentration
2.4 mmol/L,or
4.8 mEq/L or,
9.4 mg/dl
2.2-2.6 mmol/L
8.5-10.5 mg/dl

 ABC of Biochemistry 6th - P: 359

Factors regulating NaCl reabsorption from ALH:
1. It is increased by large NaCl load presented to ALH, sympathetic activity, angiotensin II & norepinephrine
2. It is decreased by prostaglandin & loop diuretics

কোন ব্যাখ্যা যোগ হয় নি।

The average blood volume of adults is about 7% of body weight, or about 5 litres. About 60% of the blood is plasma and 40% is red blood cells, but these percentages can vary considerably in different people, depending on sex, weight, and other factors.

Hypoparathyroidism leads to hypocalcemia, by decreasing the resorption of calcium from bones. Hypocalcemia causes neuromuscular hyperexcitability, resulting in hypocalcemic tetany. Normally, tetany occurs when plasma calcium level falls below 6 mg/dL from its normal value of 9.4 mg/dL.