Morphometry of the kidney in rat pups from uninephrectomized mothers

Compensatory renal growth in uninephrectomized immature rats: proliferative activity and epidermal growth factor

Compensatory response to uninephrectomy in immature animals is stronger compared with that in adult ones and the response is due mainly to renal cell proliferation. The present study explored to show the growth pattern of the remaining kidney immediately after uninephrectomy in immature rats with special reference to proliferating activity and epidermal growth factor (EGF). Immunolocalizations of proliferating cell nuclear antigen (PCNA) and EGF in immature rat kidney were examined during the first three days after uninephrectomy. Semi-quantitative analysis of the expression of preproEGF mRNA was performed. One day after the operation, the PCNA positive cell ratios in the glomeruli and the proximal tubules were significantly higher in unilaterally nephrectomized (UNx) rats than in sham-operated (Sham) rats. In UNx and Sham rats, the proximal and distal tubular cells showed positive reactions to EGF antibody. The positive reaction of proximal tubules to EGF antibody was weaker in UNx than in Sham rats 1 day after the operation, while the degree of reactivity was not different between UNx and Sham rats 3 days after the operation. The level of expression of preproEGF mRNA in the kidney was significantly lower in UNx than in Sham rats 1 day after the operation. These results indicate that unilateral nephrectomy in immature rats causes increased proliferative activity and decreased expression of EGF in the remaining kidney during the early period of compensatory renal growth.

Glomerular hypertrophy in offspring of subtotally nephrectomized ewes

We have shown that fetuses whose mothers underwent subtotal nephrectomy (STNx) before pregnancy had high urine flow rates and sodium excretions, but lower hematocrits, plasma chloride, and plasma renin levels compared with controls. To see if these functional differences in utero persist after birth and are the result of altered renal development, we studied 8 lambs born to STNx mothers (STNxL) and 10 controls (ConL) in the second week of life. These lambs were of similar body weights, nose-rump lengths and abdominal girths. Their kidney weights were not different (ConL 36.1 +/- 1.9 vs. STNxL 39.8 +/- 3.3 g), nor were kidney dimensions or glomerular number (ConL 423,520 +/- 22,194 vs. STNxL 429,530 +/- 27,471 glomeruli). However, STNxL had 30% larger glomerular volumes (both mean and total, P < 0.01) and there was a positive relationship between total glomerular volume and urinary protein excretion (P < 0.05) in STNxL. Despite this change in glomerular morphology, glomerular filtration rate, tubular function, urine flow, and sodium excretion rates were not different between STNxL and ConL, nor were plasma electrolytes, osmolality, and plasma renin levels. Thus while many of the functional differences seen in late gestation were not present at 1-2 weeks after birth, the alteration in glomerular size and its relationship to protein excretion suggests that exposure to this altered intrauterine environment may predispose offspring of mothers with renal dysfunction to renal disease in adult life.

Interactions between maternal subtotal nephrectomy and salt: effects on renal function and the composition of plasma in the late gestation sheep fetus

Effects of altered maternal salt intake between 122 and 127 days gestation (term is 150 days) were studied in eight fetuses carried by ewes which had renal insufficiency caused by subtotal nephrectomy (STNxF) and seven fetuses carried by intact ewes (IntF). Plasma sodium and osmolality were increased in ewes with subtotal nephrectomy on a high-salt intake (0.17 m NaCl in place of drinking water for 5 days; P < 0.05). The STNxF had normal body weights. A high maternal salt intake did not affect fetal blood pressure or heart rate. Plasma osmolality was higher in STNxF (P < 0.001), and plasma sodium and osmolality were increased by high salt (P < 0.001 and P < 0.04, respectively). The STNxF had higher urinary osmolalities (P = 0.002), which were also increased by a high maternal salt intake (P = 0.03). Renal blood flow fell in STNxF in response to a high maternal salt intake, but increased in IntF (P = 0.003). In STNxF but not IntF, glomerular filtration rate and urinary protein excretion were positively related to fetal plasma renin levels (P < or = 0.01). It is concluded that the salt intake of pregnant ewes with renal insufficiency affects maternal and fetal osmolar balance, fetal plasma sodium and fetal renal function. Since STNxF also had altered renal haemodynamic responses to high maternal salt and evidence of renin-dependent glomerular filtration and protein excretion, we suggest that interactions between dietary salt and pre-existing maternal renal disease impair glomerular integrity and function in the fetus.

Maternal renal insufficiency alters plasma composition and renal function in the fetal sheep

To determine the effects of chronic maternal renal insufficiency on fetal renal function, we studied nine fetuses whose mothers underwent subtotal nephrectomy at least 2 mo before mating (STNxF) and seven fetuses from intact ewes (IntF) (126-128 days of gestation, term 150 days). STNxF had lower hematocrit (P < 0.05), plasma chloride (P < 0.01), and creatinine levels (P < 0.01), and the length-to-width ratio of their kidneys was reduced (P < 0.05). They excreted twice as much urine (P < 0.05) and sodium (P < 0.01). Total (P = 0.01) and proximal fractional sodium reabsorptions (P < 0.05) were lower in STNxF; distal delivery of sodium (P < 0.05) and distal fractional sodium reabsorption (P < 0.05) were higher. They tended to have suppressed renin levels (P = 0.06). Infusions of amino acids (alanine, glycine, proline, and serine at 0.32 mmol/min for 1 h and 0.64 mmol/min for 2 h intravenously), known to stimulate renal blood flow and glomerular filtration rate in fetal sheep, did so in IntF (P < 0.01). Arterial pressure also increased (P < 0.01). These effects were not observed in STNxF. In summary, chronic maternal renal insufficiency was associated with profound alterations in fetal renal excretion of fluid and electrolytes and impaired renal hemodynamic and glomerular responses to amino acid infusion. Whether these marked changes in the renal function of fetuses carried by STNx ewes are associated with alterations in renal function in postnatal or adult life remains to be determined.

Effects of maternal uninephrectomy on the development of fetal rat kidney: apoptosis and the expression of oncogenes

The present study was designed to explore whether maternal uninephrectomy affects development of the collecting ducts in fetal kidney. Localization of DNA fragmented cells in the kidney of fetal rats from uninephrectomized mothers were examined by the terminal deoxynucleotidyl transferase (TdT)-mediated d-UTP-biotin nick end labeling (TUNEL) method. Immunohistochemistry was used to examine the localizations of bcl-2 gene products. The gene expressions for bcl-2, p53, and WT1 mRNAs were examined by using the semi-quantitative reverse transcript-polymerase chain reaction. TUNEL positive cells were more numerous in the medullary collecting ducts of the fetuses from uninephrectomized mothers than in those of the fetuses from sham-operated ones. The expressions of bcl-2, p53, and WT1 mRNAs were lower in the fetuses from uninephrectomized mothers than in the fetuses from sham-operated ones. Cells in the medullary collecting ducts showed positive reactions to anti-bcl-2 gene products antibody with the reactions being weaker in the fetuses from uninephrectomized mothers. These results showed that maternal uninephrectomy accelerated the development of fetal rat kidney and it was associated with the lowered the expression of bcl-2 in fetal rat kidney.

Perinatal development of the rat kidney: apoptosis and epidermal growth factor

Localization of apoptotic cells in the kidney of perinatal rats was examined by the terminal deoxynucleotidyl transferase-mediated d-UTP-biotin nick end labeling (TUNEL) method and electron microscopy. Perinatal changes in the percentage of kidney cells with DNA fragmentation were determined by flow cytometric analysis. Through observation of two successive sections, the relationship between the localization of the epidermal growth factor receptor (EGFR) positive cells and TUNEL positive cells in the kidney was determined. From fetal day 18 to neonatal day 5, TUNEL positive cells were noted in immature glomeruli, collecting ducts and interstitium. Electron microscopically, chromatin condensed nuclei and apoptotic bodies were seen in the same tissue component as the TUNEL positive cells. The percentage of DNA fragmented cells significantly increased from fetal days 18 to 20 and significantly decreased from fetal days 20 to 22, while they still remained low in the neonatal period. The TUNEL positive cells in immature glomeruli and collecting ducts were not reactive to the EGFR antibody. The TUNEL positive cells were not observed in the proximal tubular cells, which were positive to EGFR antibody. These results indicate that apoptotic cells are present in the kidney throughout the perinatal period in the rat and that EGF plays an important role in perinatal development of the rat kidney.

Quantitative study of the comma-shaped body, S-shaped body and vascularized glomerulus in the second and third human gestational trimesters

BACKGROUND

The rat developing metanephros has been quantified, but not the human developing kidney.

AIMS

To contribute to the knowledge of the human developing kidney by studying the relative growth of the glomerular structures subtypes in the last two gestational trimesters.

MATERIAL AND METHODS

The glomerular compartment of 21 human fetal left kidneys was studied. A stereological study determined the volume density (V(V)), the surface density (S(V)), and the numerical density in the plane (N(A)) of the developing glomeruli in the stages of comma-shaped body (C), S-shaped body (S), and vascularized glomerulus. Growth curves used log-transformed data and the allometric model.

RESULTS

Reduction of both C and S bodies, and, consequently, a relative growth of the vascularized glomerulus from the second to the third trimesters. The differences between ages were not significant to the S body V(V) and S(V), but there was a significant N(A) reduction from the second to the third trimesters. An age-related reduction of the C body and an intense growth of the vascularized glomerulus were observed in this period. The allometric coefficient b was negative in both C and S bodies and positive in the vascularized glomerulus in the last two gestational trimesters.

CONCLUSION

The growth equations and the observed tendencies of these glomerular subtypes in human fetal life could be useful to assess the kidney maturity through invasive or noninvasive investigative methods in the future.

Effects of maternal uninephrectomy on the development of fetal rat kidney: numerical and volumetric changes of the glomerulus and formation of the anionic site in the glomerular basement membrane

Developmental processes of the fetal rat kidney from uninephrectomized mothers were studied. The uninephrectomy was performed on day 5 of gestation. Glomerular number and volume in the fetal kidneys on days 18, 20, and 22 of gestation were morphometrically determined. To investigate the anionic site formation in the glomerular basement membrane, distribution of cationized ferritin (CF) in the fetal glomerulus was examined electron microscopically after CF injection. Blood urea nitrogen (BUN) concentration in the pregnant rats was also determined on various days after uninephrectomy. On fetal days 20 and 22, the glomerular volume was significantly larger in the fetuses from uninephrectomized mothers than in those from sham-operated ones. On fetal day 20, the CF particles were clustered in the laminae rarae interna and externa of the glomerular basement membrane in the fetuses from uninephrectomized mothers, while the clusters were arrayed in three to four layers in the glomerular basement membrane in the fetuses from sham-operated ones. On fetal day 22, the CF particles noted in the lamina rara externa in the fetuses from uninephrectomized mothers were slightly larger in number than such particles in the age-matched control fetuses. The BUN concentration of the uninephrectomized pregnant rats was significantly higher than that of the sham-operated pregnant ones on each postoperative day. These results suggest that the development of the fetal renal glomerulus is accelerated by the elevated BUN level following maternal uninephrectomy when the fetal kidney is functional in effective filtration in the rat.