Changes in Renal Function and Blood Volume in the Newborn Lamb Delivered by Cesarean Section

Abstract

To determine the cause of the transient natriuresis in lambs within 1-2 h of birth, renal function and blood volume (BV) were measured in nine chronically catheterized fetal sheep aged 139-145 d before and after delivery by cesarean section. After delivery, sodium excretion increased &fold. This was due to a transient rise in glomerular filtration rate (by 39 + 21%, p < 0.02) and a fall in fractional reabsorption of sodium by the proximal tubule from 63.4 2 2.5% to 53.4 + 3.4% @ < 0.01). The distal tubule failed to compensate fully for this fall, because fractional reabsorption by the distal tubule rose from 35.5 2 2.4% to only 41.6 2 2.2% @ < 0.05). The extent of the natriuresis did not depend on the lamb's initial BV per kg at birth. However, the amount of fluid excreted and the clearance of sodium during a 45-min period within the first 1-1.25 h after birth were approximately equal to the fall in BV that occurred during this time. Thus, most of the fall in After birth, human infants have a transient increase in urine flow rate (1). Similarly, lambs delivered by cesarean section at 139-145 d have a transient natriuresis and disruption of glomerulotubular balance (2). It has been suggested that volume expansion of the newborn, resulting from placental blood transfusion, may contribute to this diuresis (3). We postulated that lambs with larger BV relative to their weights would show a greater natriuresis than lambs with smaller BV per kg body weight. It should be noted that because it was not possible to measure partitioning of the fetal BV between the fetal body and the placenta before birth, it could not be determined whether placental transfusion occurred with delivery.

Tubuloglomerular feedback response in the prenatal and postnatal ovine kidney

“…Consistent with data in several studies, renal function in terms of GFR was greatly depressed in the fetal kidney compared with the lambs (3,13,23,28,33,36). Marked hemodynamic changes take place within the kidney between the prenatal and postnatal period.…”

Organic and inorganic selenium: IV. Passive transfer of immunoglobulin from ewe to lamb1

“…According to Quigley et al (1998), BW is the best predictor of plasma volume. The conversion factors for blood volumes vary among studies, breeds, and species between 5% and 15% of BW (Gibson and Lumbers, 1994;Quigley et al, 1998;Rumball et al, 2008). Total IgG transferred Supranutritional Se 0.93 0.08 0.10 0.78 0.73 0.006 1 Ewe blood samples were collected within 30 d of lambing.…”

Extracellular volume and blood volume in chronically catheterized fetal sheep.

“…We did not attempt to study the division of the ECV between the fetal body and extrafetal tissues. However, since up to 30 % of the BV can be contained within the extra-fetal tissues (Barcroft & Kennedy, 1939;Gibson & Lumbers, 1994), it is possible that these tissues may also have a relatively high ECV,…”