Identification of an atypical lipoprotein-binding protein from human aortic smooth muscle as T-cadherin.

We have previously described an atypical lipoprotein-binding protein of about 105 kDa (p105) in membranes of vascular smooth muscle cells (VSMCs) that is distinct from currently known lipoprotein receptors. In the present work we have developed a procedure for purification of p105 from human aortic media. Partial sequencing of purified protein has revealed identity of p105 with human T-cadherin. Anti-peptide antisera raised against human T-cadherin recognized a protein spot corresponding to the purified p105 on two-dimensional Western blots. The antisera also inhibited LDL binding to p105 on ligand blots. We conclude that the 105 kDa lipoprotein-binding protein present in human VSMCs is T-cadherin, an unusual glycosylphosphatidylinositol-anchored member of the cadherin family of cell-cell adhesion proteins.

[Use of hepatocytes cultured in microcarriers for correction of acute hepatic insufficiency]. / Ispol'zovanie kul'tiviruemykh na mikronositeliakh gepatotsitov dlia korrektsii ostroi pechenochnoi nedostatochnosti.

The ability of hepatocytes cultured on Biosilon microcarriers to secrete albumin and to conjugate bilirubin were examined for the purpose of developing an artificial liver support system. Cultured hepatocytes were able to synthesize 100-120 micrograms albumin per 10(5) cells in 24 hours and to conjugate about 20 micrograms/hr of bilirubin for at least 5 days. Rats with liver failure caused by i.p. injection of CCL4 or D-galactosamine were subjected to hemosorption via minicolumns containing 2 ml of Biosilon microcarriers with 40 X 10(6) cultured hepatocytes. The procedure was performed 20-24 h after hepatotoxins injection and lasted for 3 h at a flow rate of 60 ml/h. This reduced mortality from 100% to 20% after 48% and to 40% after 7 days in case of CCl4 and from 100% to 40% after 48 h and 7 days in case of D-galactosamine. Our results suggest that hepatocytes cultured on microcarriers may be efficiently applied to correction of fulminant hepatic failure caused by different hepatotoxins.

In vivo and in vitro estimations of the direct effect of estrogen on rat hepatocytes tested by the changes in the unusual estrogen-binding protein content.

The direct effect of estradiol (E2) on the hepatocytes of mature male rats has been examined by measuring the changes in the unusual estrogen-binding protein (UEBP) content and parallel measuring the level of liver estrogen receptors (ER). The content of UEBP (NUEBP) and ER (NER) in the liver were determined using the quantitative methods for differential specific determination of the E2-binding sites of these proteins. It has been shown that the administration of E2 in vivo induced a considerable decrease in hepatic NUEBP not only in intact males, but also in hypophysectomized males during the initial period after the operation (when the content of hepatic ER was still high) and produced no effect in hypophysectomized males during the later period (when liver ER were depleted). Repeated administration of human growth hormone (hGH) (twice a day) resulted in a considerable increase in NER in hypophysectomized males and restored the sensitivity to the subsequent inhibitory effect of E2 on UEBP. We also used rat hepatocytes after a 4-day primary culturing. These cells had a stable morpho-functional status, high ER level, and sex-differentiated UEBP content. Culturing of mature male rat hepatocytes in the medium containing E2 at concentrations close to physiological levels (10(-10)-10(-7) M) decreased NUEBP in a dose-dependent manner. Hexestrol (10(-7) M) but not cholesterol (10(-5) M) also exhibited a direct effect on NUEBP in cultured rat hepatocytes. The effect of E2 was reversible: statistically significant increase in NUEBP was observed 3 days after 10(-9) M E2 had been removed from the culturing medium. It was concluded that hepatocytes may be a primary target for E2 under physiological conditions and that GH may modulate the direct effect of E2 at the hepatic level by modifying the content of liver ER.

[Estimation of a direct regulatory effect of estrogens on hepatocytes, evaluated according to the change in the level of free estrogen-binding protein in primary cell culture]. / Vyiavlenie priamogo reguliatornogo deistviia éstrogenov na gepatotsity, otsenivaemogo po izmeneniiu urovnia osovogo éstrogensviazyvaiushchego belka v pervichnoi kulture kletok.

Male rat hepatocyte cultures have been obtained. The culturing hepatocytes had a stable level of some morphological and functional properties. A high level of estrogen receptors (ER) and E2-sensitive unusual estrogen-binding protein (UEBP) was found. A direct dose-dependent inhibiting effect of physiological (10(-10)-10(-7) M) concentrations of E2 on UEBP content was established in cell cultures incubated with the hormone for 3 days. Hexestrol (but not cholesterol) was found to exert a direct inhibiting effect. The inhibiting effect of E2 (10(-9) M) was observed after a 24 hour incubation of hepatocytes with the hormone but was less pronounced. In this case a significant increase in UEBP concentration in hepatocytes was noted 72 hours after the removal of E2. It is concluded that physiological concentrations of E2 can exert a direct regulatory influence on certain functions of culturing hepatocytes acting via hepatocyte ER.