Morphometrical Studies on Perinatal Development of Glomerular Components in Rat

Abstract

Perinatal development of rat glomerulus was studied morphometrically. The percentage volumes of the five glomerular components (epithelial cells, capillary, mesangium, glomerular basement membrane, and Bowman’s space) were determined by point counting and the surface area of glomerular basement membrane per unit volume of glomerulus was done by intercept counting. Percentage volume of Bowman’s space was significantly decreased between days 20 and 21 of gestation, indicating the rapid growth of glomerular tuft during the prenatal period. Though both the length of glomerular capillary per unit volume of glomerulus (L_v) and surface area of glomerular basement membrane per unit volume of glomerulus were gradually increased from fetal day 20 to neonatal day 3, remarkable increase in L_v was observed between fetal day 22 and neonatal day 1. This indicates that the rat glomerulus develops rapidly during this period to adapt to extrauterine environment after birth.

Effects of maternal bilateral ureteral ligation on fetal development of kidney in rats: Morphometrical changes in glomerular components

“…Considering our previous report that SVi and L, increase during perinatal days in rats, accompanying significant increase in L, between fetal day 22 and neonatal day 1 (Okada and Morikawa, 1990b), the present result demonstrating significant differences in SVi and L, between the two groups (E > C) on fetal days 20 and 22 indicates that maternal bilateral ureteral ligation elevates renal functional demand in glomerular filtration in the fetus. This is supported by the report of Matsuo et al (1986) that, when maternal ureters have been ligated for 24 hr, BUN concentrations in the ligated mothers and the fetuses are about five times those in sham-ligated mothers.…”

“…Morphometric analyses were performed by the methods described in our previous report (Okada and Morikawa, 1990b). The inner edge of parietal layer of Bowman's capsule was considered as the border of a glomerulus.…”

“…However, several line of evidence suggest that the fetal kidney is functional in rats: the kidney secretes urine during late in gestation (Bakala et al, 1985;Schaeverbeke and Cheignon, 1980;Wells, 1946a); increased maternal blood urea nitrogen (BUN) following bilateral ureteral ligation for 1 day in pregnant rats stimulates function of the fetal kidney (Matsuo et al, 1986); maternal bilateral ureteral ligation increases the number of functional glomeruli in fetal rats (Okada and Morikawa, 1988); and maternal ureteral ligation also accelerates the development of the proximal tubule in the fetus (Okada and Morikawa, 1990a). Furthermore, in perinatal rats, the glomerulus shows two developmental characteristics in morphology: the rapid growth of the glomerular tuft during late gestation and the remarkable increase in the length of glomerular capillary per unit volume of glomerulus immediately after birth (Okada and Morikawa, 1990b). These findings led us to explore possible changes in the development of cellular components of glomerulus as a consequence of maternal renal dysfunction.…”

Effects of maternal bilateral ureteral ligation on the development of the proximal tubule of the kidney in fetal rats: Morphometry and electron microscopic study

“…In the rat kidney, glomerular filtration starts on fetal day 18 (Schaeverbeke and Cheignon, 1980), effective filtration does not start until fetal day 20 (Bakala et al, 1985), and glomerular capillary tufts grow rapidly from fetal days 20 through 21 (Okada and Morikawa, 1990). Further, the elevated glomerular function accelerates the development of the proximal tubule (Okada and Marikawa, unpublished observation).…”

“…We have recently divided the development of the fetal kidney into two stages: the glomerular neogenetic stage from fetal days 16 through 18 and the glomerular maturation stage from fetal days 18 through 22 (Okada and Morikawa, 1988a). In the rat kidney, glomerular filtration starts on fetal day 18 (Schaeverbeke and Cheignon, 1980), effective filtration does not start until fetal day 20 (Bakala et al, 1985), and glomerular capillary tufts grow rapidly from fetal days 20 through 21 (Okada and Morikawa, 1990). Further, the elevated glomerular function accelerates the development of the proximal tubule (Okada and Marikawa, unpublished observation).…”