We examined the distribution and maturational changes of carbonic anhydrase I (CAI) and carbonic anhydrase II (CAII) in microdissected nephron segments of Sprague-Dawley rats. CAI and CAII proteins were measured by enzyme-linked immunosorbent assay. CAI was not detected in any nephron segment in 7-week-old rats. CAII was present in the collecting ducts, proximal tubules, and thick ascending limbs of loop of Henle in 7-week-old rats. CAII contents were significantly higher in the early proximal tubules (S1) than in second (S2) and late (S3) portions of the proximal tubules, while the contents in S1 were less than in cortical collecting ducts (CCD), outer stripe and inner stripes of the outer medullary collecting ducts (OMCDo and OMCDi). CAII content in each of S1, CCD, and OMCD of 1-week-old rats was only 14% or less of that of adults, but increased steeply during the 2nd and 3rd weeks of life, reaching almost 40% at 3 weeks of age and 97% at 7 weeks. Our results indicate that CAII is present throughout the entire nephron of the rat, and that CAII content in S1, CCD, and OMCD increases exponentially during the first 7 weeks of life. Our data suggest that the immature low levels of CAII may explain, at least in part, the limited capacity of urinary acidification during neonatal life. Further studies are necessary to establish the role of such changes in CAII content in acid-base homeostasis during neonatal life.

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Using a combination of gene amplification with single strand conformation polymorphisms analysis and sequencing, we examined the COL4A5 gene in 37 patients with Alport syndrome. In patient A8, a single base insertion was noted at codon 1,597 tyrosine in exon 49. The premature terminal signal appeared and 89 amino acids (approximately one-third) of the non-collagenous domain were lost. The mutation was present in the mother, hence she is heterozygous. In patient A12, the nucleotide changed from C to T at codon 1,679 glutamine in exon 51, which created a termination codon, and 7 amino acids at the carboxyl terminus were lost. Gene tracking using peripheral leukocytes revealed that the parents did not carry the mutant allele, while the sister was heterozygous. DNA samples from hair roots and skin fibroblasts of the mother were normal and immunological examination of the epidermis of the mother indicated that the alpha 5(IV) chain was normally expressed. As these results suggest that somatic cells of the mother do not carry the mutant allele, the primordial germ cells possibly carry a fresh mutation in the mother of patient A12.

We examined the differential expressions of collagen types IV, 111, and I in the developing feto-maternal placental tissue of pregnant rats by a combination of in situ hybridization and immunohistochemistry. At day 9.5 of gestation, polygonal invasive cytotrophoblasts from the ectoplacental cone, which was modifying the maternal central artery, revealed intensely expressed al(1V) and al(II1) collagen mRNAs. The localization patterns of these translated products, collagen type IV and procollagen type 111, were slightly different in the invasive cytotrophoblasts. Collagen type IV densely deposited intracellularly and intercellularly in the maternal central artery and in the thickened basement membranes of the cytotrophoblasts. However, expression of al(1) collagen mRNA and procollagen type I was hardly detectable in the cytotrophoblasts. At day 13 of gestation, a high level of al(1V) collagen mRNA was expressed in the cytotrophoblastic cell layer (trophospongium) and in the invasive large cytotrophoblasts. A moderate level of al(II1) collagen mRNA wag also expressed mainly in the cytotrophoblasts, while d(1) collagen mRNA was expressed at very low levels. Interestingly, procollagen type I11 failed to show linear immunoreactivity in the subepithelial extracellular matrix beneath the maternal artery with the invasive cytotrophoblasts. Additional quantitative analyses of these type IV, 111, and I collagen mRNA levels in in situ hybridization experiments between several cell types also revealed significant differences individually. Electron-microscopic study detected no cross-striated collagen fibers in the thickened basement membrane-like structures adjacent to the invasive cytotrophoblasts. Fibrillar and baaement membrane collagen gene expressions, their protein syntheses, and the processing of these procollagens seem to be developmentally regulated in the invasive cytotrophoblasts during the organization of feto-maternal placental tissue. The remodeling of the maternal central artery by the invasive cytotrophoblasts is important for ensur-0 1996 WILEY-LISS, INC.ing the adequate blood supply to the developing placenta and fetus. 6 1998 Wiley-Liss, Inc.

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We examined the differential expressions of collagen types IV, III, and I in the developing feto‐maternal placental tissue of pregnant rats by a combination of in situ hybridization and immunohistochemistry. At day 9.5 of gestation, polygonal invasive cytotrophoblasts from the ectoplacental cone, which was modifying the maternal central artery, revealed intensely expressed α1(IV) and α1(III) collagen mRNAs. The localization patterns of these translated products, collagen type IV and procollagen type III, were slightly different in the invasive cytotrophoblasts. Collagen type IV densely deposited intracellularly and intercellularly in the maternal central artery and in the thickened basement membranes of the cytotrophoblasts. However, expression of α1(I) collagen mRNA and procollagen type I was hardly detectable in the cytotrophoblasts. At day 13 of gestation, a high level of α1(IV) collagen mRNA was expressed in the cytotrophoblastic cell layer (trophospongium) and in the invasive large cytotrophoblasts. A moderate level of α1(III) collagen mRNA was also expressed mainly in the cytotrophoblasts, while α1(I) collagen mRNA was expressed at very low levels. Interestingly, procollagen type III failed to show linear immunoreactivity in the subepithelial extracellular matrix beneath the maternal artery with the invasive cytotrophoblasts. Additional quantitative analyses of these type IV, III, and I collagen mRNA levels in in situ hybridization experiments between several cell types also revealed significant differences individually. Electron microscopic study detected no cross‐striated collagen fibers in the thickened basement membrane‐like structures adjacent to the invasive cytotrophoblasts. Fibrillar and basement membrane collagen gene expressions, their protein syntheses, and the processing of these procollagens seem to be developmentally regulated in the invasive cytotrophoblasts during the organization of feto‐maternal placental tissue. The remodeling of the maternal central artery by the invasive cytotrophoblasts is important for ensuring the adequate blood supply to the developing placenta and fetus. © 1996 Wiley‐Liss, Inc.

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