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Radioautographic determinations of 125I-[Tyr0,D-Trp8]somatostatin-14 (125I-SRIF) binding sites were performed on frozen serial sections of the locus coeruleus (LC) of control rats and of rats subjected to either bilateral microinjections of 6 hydroxydopamine (6-OHDA) into the LC or unilateral microinjection into the ascending noradrenergic bundles. These experiments were performed in order to determine whether 125I-SRIF binding was localized to noradrenergic-containing cells and in which regions the cells which contain the binding sites are projecting. The extent of the lesions was assessed by measuring norepinephrine (NE) levels in the hippocampus (88% decrease as compared to sham-operated animals) for bilateral LC lesions and in the frontal cortex (87% reduction vs. contralateral side) for unilateral bundle lesions. In control rats, 125I-SRIF binding sites were restricted to the boundaries of the LC and followed closely the distribution of tyrosine hydroxylase-labeled cells. Three weeks after bilateral injections of 6-OHDA, 125I-SRIF binding decreased by 79% in all regions of the LC. In contrast, unilateral destruction of the ascending noradrenergic bundles resulted in a moderate decrease only in the middle part of the LC with a more important effect in the dorsal (55%) than in the ventral (24%) portion of the nucleus. These data demonstrate that: 1) most SRIF receptors in the LC are located in the vicinity of NE-containing cell bodies and 2) NE-containing cells bearing SRIF receptors project to the forebrain as well as to other terminal areas located more caudally in the brain. These data suggest a general role for SRIF in the control of the multiple functions of the LC.

Ontogenesis of the glomerular C3b receptor (CR1) was studied in kidneys from 16 fetuses aged from 9 to 32 weeks, using immunohistochemical techniques and the F(ab′)2 fragment of a monospecific rabbit antibody to CR1, and adherence of C3b-coated sheep erythrocytes. By indirect immunofluoresence, anti-CR1 stained presumptive glomerular epithelium from the end of the S-body stage of nephron differentiation. Staining increased with visceral epithelial cell proliferation and with differentiation of the nephron from the subcortical to the juxtamedullary part of the fetal kidney. Using electron microscopy and an indirect immunoperoxidase technique, CR1 antigen was detected on the plasma membrane in the basolateral part of primitive podocytes from the late S-body stage, following the acquisition by podocytes of the capacity to synthetize a basal lamina. Endothelial cells and mesangial cells did not stain for CR1 antigen. CR1 antigen was expressed by podocytes from the same stage of glomerular differentiation as was the CALLA antigen. Glomerular expression of CR1 on podocytes preceded that of Ia on glomerular endothelial cells. C3b-bearing sheep erythrocytes only adhered to clover-like lobulated glomeruli at a late stage of glomerular differentiation. Glomerular CR1, a specific marker of glomerular capillary epithelial cells is one of the earliest markers expressed by resident glomerular cells during renal ontogenesis.

Ontogenesis of 28kDa vitamin D-induced calcium–binding protein in human kidney. The kidney distribution of 28kDa vitamin D-induced calcium binding protein (CaBP) was studied in 15 fetuses (11 to 33 weeks old), six children and adults (12 days to 32 years old) by immunocytochemistry using a specific antibody to rat renal 28kDa CaBP. Similar results were obtained on frozen and fixed tissues. Kidneys from one adult and three fetuses were studied by immunoelectronmicroscopy for antigen localization at the subcellular level using the indirect immunoperoxidase technique. The 28kDa CaBP was present in all kidneys from the eleventh week of gestation. At that stage, all deep parts of collecting ducts were homogeneously stained and a few distal tubules located in the deep cortex were intensely labeled. No labeling was observed in the early stage of nephron differentiation (S-body). 28kDa CaBP distribution changed with kidney maturation. There was a progressive reduction of the deep part of collecting duct labeling and a concomitant increase in the number and intensity of stained distal tubular cells. At the ultrastructural level, 28kDa CaBP was observed in the cytosol and the nuclear euchromatin. Our study demonstrates the early cellular synthesis of 28kDa CaBP and its transient expression by deep collecting duct cells during early fetal life, at a time when only a few distal convoluted tubular cells synthetize it.

Ontogenesis of angiotensin-I converting enzyme in human kidney. The kidney distribution of angiotensin-I converting enzyme (ACE) was studied in 14 fetuses (11 to 30 weeks old) and 7 children (2 days to 13 years old) by immunohistochemistry using specific antibodies to human kidney ACE. Immunohistochemical techniques included indirect immunofluorescence on cryostat sections of frozen tissue, immunoper-oxidase and immunofluorescence of fixed tissue embedded in Paraplast, and immunoelectron microscopy. The ACE distribution in the fetal kidneys was independent of the age of the fetus. ACE was detected in two locations: 1) on the basolateral membranes and primary apical microvilli of epithelial cells from early differentiating proximal tubules; the labeling was intense in brush borders of fully developed proximal tubules; and 2) on glomerular endothelial cells; cells were lined by reaction product as soon as capillaries invaded the inferior cleft of the S-shaped body. Tubular ACE distribution was identical in the postnatal kidneys. The staining of the glomerular endothelium was extremely inconstant. The presence of ACE in proximal tubular cells and glomerular endothelial cells at the beginning of nephron differentiation may indicate that it is involved in the development of nephron function and renal hemodynamic.