A plasma protein fractionation procedure for use in studies of protein metabolism

A two-step method for the separation of five different plasma proteins on a preparative scale, which is capable of being extended to allow the separation of other plasma proteins, is described. The proteins separated were fibrinogen, two alpha(1)-glycoproteins, albumin and transferrin. The alpha(1)-glycoproteins were characterized in terms of electrophoretic mobility, ultracentrifugal and immunological characteristics. By using this method, it was shown that a single sample of plasma could be fractionated to yield purified proteins in sufficient quantity to simultaneously measure the synthesis of the two alpha(1)-glycoproteins, albumin and transferrin in the rat with McFarlane's technique (McFarlane, 1963; Reeve et al., 1963; McFarlane et al., 1965).

The effect of cortisol on the synthesis of rat plasma albumin, fibrinogen and transferrin

A decrease of absolute synthesis of albumin, no change in that of fibrinogen and an increased fractional synthesis of transferrin were observed 3h after intraperitoneal administration of a pharmacological dose of 5 mg of cortisol to 220g rats in the post-absorptive state and previously kept on a diet with 40% protein. The concentration in liver of total free amino acids was practically unchanged at this time. Intraperitoneal administration of a mixture of amino acids with the cortisol raised this concentration and was accompanied by an almost complete de-repression of the synthesis of albumin, with no real effect on that of fibrinogen. In considerable contrast, in rats studied at 24h after intraperitoneal administration of cortisol, and who had been fed once in the interim (but who had received no amino acids intraperitoneally), there was a marked increase in the absolute synthesis of albumin and fibrinogen, with an increase in fractional synthesis that was less proportionately but still very significant and which included transferrin. The amino acid concentrations had risen above the supplemented values at 3h but not as much proportionately as the fractional synthesis rates, and of course not as much as the absolute synthesis rates, of albumin and fibrinogen. These time-dependent effects of cortisol suggest to us that our studies resolve the apparently conflicting results of the effect of cortisol on the synthesis of albumin reported by others.

The acute effect of ethanol on albumin, fibrinogen and transferrin synthesis in the rat

Decrease of absolute synthesis of albumin and fractional synthesis of transferrin was observed within 3h of orally administering ethanol (4ml/kg) to rats maintained on a 40%-protein diet. In contrast, absolute synthesis of fibrinogen was unaffected. With this ethanol intake, the changes in protein synthesis occurred without significant ultrastructural change in the liver. When the ethanol intake was greater (8ml/kg) ultrastructural disruption was observed. However, both the decrease of plasma protein synthesis and the ultrastructural alterations could be prevented by the simultaneous administration of a mixture of amino acids with the ethanol. The latter findings, not reported hitherto, suggest that ethanol may interfere with hepatic plasma protein synthesis and ultrastructure more through a disturbance of amino acid metabolism than through direct physical damage to the hepatocyte. An Appendix outlines the deconvolutional method used to correct for losses of labelled protein in the period during which measurements were made. The principle may also be applied to labelled plasma urea. The details of the calculations are given in a supplementary paper that has been deposited as Supplementary Publication 50007 at the National Lending Library for Science and Technology, Boston Spa, Yorks. LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1972) 126, 5.

Fine structural aspects of the mobilization of hepatic glycogen. II. Inhibition of glycogen breakdown

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