S U M M A R YRecent studies suggest important functions for laminin-8 (Ln-8; ␣ 4 ␤ 1 ␥ 1) in vascular and blood cell biology, but its distribution in human tissues has remained elusive. We have raised a monoclonal antibody (MAb) FC10, and by enzyme-linked immunoassay (EIA) and Western blotting techniques we show that it recognizes the human Ln ␣ 4-chain. Immunoreactivity for the Ln ␣ 4-chain was localized in tissues of mesodermal origin, such as basement membranes (BMs) of endothelia, adipocytes, and skeletal, smooth, and cardiac muscle cells. In addition, the Ln ␣ 4-chain was found in regions of some epithelial BMs, including epidermis, salivary glands, pancreas, esophageal and gastric glands, intestinal crypts, and some renal medullary tubules. Developmental differences in the distribution of Ln ␣ 4-chain were detected in skeletal muscle, walls of vessels, and intestinal crypts. Ln ␣ 4-and Ln ␣ 2-chains co-localized in BMs of fetal skeletal muscle cells and in some epithelial BMs, e.g., in gastric glands and acini of pancreas. Cultured human pulmonary artery endothelial (HPAE) cells produced Ln ␣ 4-chain as M r 180,000 and 200,000 doublet and rapidly deposited it to the growth substratum. In cell-free extracellular matrices of human kidney and lung, Ln ␣ 4-chain was found as M r 180,000 protein.

This study describes the first mutation located in the extracellular domain of an ENaC subunit associated with an increased ENaC activity and Liddle's syndrome.

Laminin has been proposed to influence the function of human adrenal cortex. We have studied the distribution of laminin (Ln) chains using immunofluorescence in human fetal and adult adrenal cortex. In the fetal gland Ln ␣2-and ␣5-chains were weakly expressed in the definitive zone, whereas Ln ␣4-, ␤1-, and ␥1-chains occurred around vessels. In the adult gland, Ln ␣2-, ␣5-, and ␥1-chains were found in epithelial basement membranes (BM) in all cortical zones, Ln ␣4-chain in vessels, Ln ␤1-chain in outer zone, and Ln ␤2-chain in the two inner zones of the cortex, respectively. Among the integrins in adult gland, integrin ␣ 3 -subunit was confined to basal surfaces of

Immunohistochemistry was used to study the distribution of laminin (Ln) chains, collagen types IV (alpha 1/2), VII, and XVIII and Lutheran antigen (Lu) in 36 frozen ovarian carcinoma samples. Surface epithelial basement membrane (BM) of the normal ovary showed immunoreactivity for Ln alpha1, alpha3-alpha5, beta1-3, gamma1, and gamma2 chains and type IV and XVIII collagens. Chains of Ln-5 (alpha3beta3gamma2) and Ln-10 (alpha5beta1gamma1) as well as type IV and XVIII collagens were found in most tumor BMs, but Ln alpha2 chain and type VII collagen were detected only in few tumors. Contrary to serous tumors, BMs of mucinous carcinomas showed Ln alpha4 chain, but not Ln alpha1 and beta2 chains. Ln alpha1 chain was found in most endometrioid carcinomas, whereas chains of Ln-5 were only moderately detectable in comparison with serous and mucinous carcinomas. In the normal ovary, Lu immunoreactivity was confined to basal aspect in the ovarian epithelial cells, but in tumor specimens Lu immunostainings showed variable polarized and nonpolarized patterns. The results suggest that the three types of ovarian carcinoma have distinct differences in their Ln distribution and can be grouped based on their expression pattern. This suggests that they may have histogenetically different precursors and may help to distinguish these tumors from each other.