Changes in Body Weight, Kidney Weight and Proximal Tubule Length during Pregnancy in the Rat

SUMMARY1. Using free-flow micropuncture techniques, the rate of reabsorption from the proximal convoluted tubules was measured in virgin, 19-day-pregnant and 6-to 7-day-lactating Sprague-Dawley rats.2. In separate groups of animals proximal convoluted tubules were filled with silicone rubber, dissected out and their lengths measured.3. Single nephron glomerular rate was increased in pregnant and lactating animals. 4. The rate of reabsorption per unit length of the proximal convoluted tubule was decreased in pregnant animals but similar in virgins and lactating rats.5. The proximal convoluted tubule was increased in length in pregnant and lactating animals. As a result the total reabsorption by the proximal convoluted tubule was similar in virgin and pregnant animals but increased in lactating animals.6. The amount reabsorbed by the loop of Henle and distal parts of the nephron is greater in pregnant and lactating animals than in virgins.

Section: Resultssupporting

confidence: 76%

Fluid reabsorption by the proximal convoluted tubule of the kidney in lactating rats.

Arthur¹,

Green²

1986

“…Reabasorption rates were not significantly different at the different stages of pregnancy (see Table 2). Taken together with the altered lengths of the proximal tubules in pregnancy (Garland et al 1978) this would imply (if reabsorption is constant along the nephron) that in pregnancy more fluid was reabsorbed by the proximal tubule because of its greater length and not because of any alteration of intrinsic reabsorptive capacity.…”

Section: Urine Flowmentioning

confidence: 99%

“…Because of the uncertainty attached to total collections of proximal tubular fluid (see above) it has not been possible to obtain direct information on proximal tubular reabsorption in the free flow condition. Data from the stationary microperfusion experiments indicate that there may be no change in intrinsic reabsorptive capacity, but since there is an increase in proximal tubular length during pregnancy (Garland et al 1978) the total reabsorption in the proximal tubule may well be raised in pregnancy. What is certain is that if there are changes in proximal fluid reabsorption these may be offset by altered reabsorption in the loop of Henle, since fractional reabsorption is the same at all stages of pregnancy by the early distal tubule and there are only small changes in absolute fluid reabsorption.…”

Section: Fluid Reabsorptionmentioning

confidence: 99%

Micropuncture study of changes in glomerular filtration and ion and water handling by the rat kidney during pregnancy

Garland

Green

1982

Self Cite

SUMMARY1. In rats receiving 200 gl. min-sodium chloride, glomerular filtration rate, single nephron glomerular filtration rate, and fractional reabsorption were measured at various points along the nephron, and ionic concentrations measured in early distal tubular fluid in virgin and 6, 12 and 19 day pregnant rats.2. Glomerular filtration increased progressively until the twelfth day ofpregnancy. At 19 days of pregnancy the glomerular filtration rate, while still above virgin levels, was reduced below 12 day pregnant levels.3. Single nephron glomerular filtration rates measured in proximal and distal tubules were different at both 12 and 19 days of pregnancy, indicating an alteration of tubuloglomerular feed-back. 4. A change in the ratio ofglomerular filtration rate: distal single nephron filtration rate indicated a redistribution of glomerular filtrate to juxtamedullary nephrons by the sixth day of pregnancy.5. Fluid reabsorption is similar up to the early distal tubule but it is not possible to say whether reabsorption is the same in proximal tubules. More fluid is reabsorbed by late distal tubules and collecting ducts in 12 and 19 day pregnant animals than in the virgin and 6 day pregnant animals.6. Changes in ion reabsorption by the loop of Henle occurred during pregnancy; sodium reabsorption was increased by the sixth day of pregnancy and potassium reabsorption by the twelfth day.

“…Thus, changes in fractional reabsorption of sodium and water that have been described for the whole kidney in pregnancy (e.g. Atherton & Pirie, 1977;Bishop & Green, 1980) are unlikely to be due to increased fractional reabsorption per unit proximal tubular length; but may be related to the increased length of the proximal tubule found in pregnancy (Garland et al 1978) or to changes in segments of nephron beyond the proximal tubule.…”

Section: Sodium and Fluidmentioning

confidence: 96%

Effects of pregnancy on glucose reabsorption by the proximal convoluted tubule in the rat.

Bishop¹,

Green²

1981

SUMMARY1. Free-flow micropuncture techniques were used to investigate glucose, sodium and water reabsorption along the proximal convoluted tubule in 7-8 day pregnant rats undergoing saline or glucose infusion and in virgin controls.2. Absolute proximal tubular reabsorption of glucose was greater in pregnant animals than virgins during both saline and glucose infusion; and fractional reabsorption of glucose was higher in pregnant than in virgin animals during glucose infusion.3. During glucose loading, less glucose escaped reabsorption in the proximal tubule in pregnant than in virgin animals. It is concluded that the increased excretion of glucose observed in pregnant rats cannot be due to failure of proximal tubular mechanisms.4. During saline infusion pregnant animals had a higher single nephron glomerular filtration rate (s.N.G.F.R.) when compared with virgin animals and a corresponding increase in reabsorption of sodium and water. The small increases in S.N.G.F.R. and sodium reabsorption in pregnant animals (compared with virgin animals) during glucose infusion were not statistically significant.5. Fractional reabsorption of sodium (and water) along the proximal convoluted tubule was not significantly different in the four series. It is concluded that glomerulo-tubular balance operates during pregnancy.