Abstract: Hepatic diseases can be prevented or treated by administering an isoprenylamine derivative represented by the general formula (II) ##STR1## [wherein n represents an integer of 4-12, m represents an integer of 0-3, Ar represents a phenyl group, a furyl group, a thienyl group or a pyridyl group, said group being optionally substituted with one or more of an alkyl group of 1-4 carbon atoms, and alkoxy group of 1-4 carbon atoms, a methylenedioxy group, a hydroxy group or a halogen atom, and R represents a hydrogen atom or an alkyl group of 1-4 carbon atoms] or a pharmacologically acceptable salt thereof at a daily dose of 0.01-500 .mu.g/kg.A lipid emulsion of the compound (II) is particularly useful and can be administered at a remarkably lowered dose as compared with other pharmaceutical preparations.

Abstract: A method for converting big endothelin-1 to endothelin-1 by contacting big endothelin-1 with a commercially available preparation of apolipoprotein B is presented. The apolipoprotein B itself has the converting enzyme activity.

Abstract: A human endothelin converting enzyme (ECE) has been isolated from blood and placenta. The enzyme has the activity of converting big endothelin-1, -2, or -3 to endothelin-1, -2, or -3 respectively. The enzyme has a mass of about 5.4.times.10.sup.5 by gel filtration, a pH optimum of 6.5 to 7.5, and a hydrated density of less than 1.210. The enzyme is inhibited by EDTA, phosphoramidon, thiorphan, chymostatin and phenylmethylsulfonylfluoride (PMSF). The enzyme is precipitated by 0.65% dextran sulfate or 0.2M manganese chloride. The enzyme can be inactivated by oxidation by copper ion.

Abstract: Human endothelin converting enzyme (ECE) has been isolated from blood or placenta by a series of centrifugation steps at different densities. A first ECE-I is isolated by a low speed centrifugation to produce enzyme with a hydrated density of about 0.94 g/ml. A second high speed centrifugation produces an ECE-II with a hydrated density between about 0.94 to about 1.006 g/ml. After adjusting the density of the solution, a high speed centrifugation isolates an ECE-III with a hydrated density between about 1.006 to about 1.063. A final adjustment to the density of the solution and high speed centrifugation obtains an ECE-IV with a hydrated density of between about 1.063 to about 1.210 g/ml.