Effects of insulin and of glycerol in vitro on the incorporation of [carboxy-14C]acetate into the fatty acids of lactating mammary gland slices with special reference to species differences

Abstract

activators though less so than magnesium. Potassium ions are inactive in this respect. 3. The pH optimum of the enzyme for the forward reaction, i.e. the splitting of phosphocreatine in the presence of adenylic acid lies in the range of 5*9-7; phosphocreatine is split optimally at the same pH range when adenosinediphosphate is used as the phosphate acceptor. 4. Preparations from brain also catalyse the synthesis of phosphocreatine from creatine and adenosinetriphosphate above pH 8-2. 5. None of the drugs of central action which were examined had any significant effect on the activity of the enzyme. Iodoacetate inhibited it completely above a concentration of 05 mm and fluoride to a much less marked degree. I wish to thank Dr McIlwain for having suggested the problem and for many helpful discussions.

The effect of fumarate and of p-nitrophenol on the synthesis of fatty acids in homogenates of the mammary gland

“…Effect of gluco8e and pyruvate on the metaboli8m of [carboxy-14C]acetate. Balmain et al (1952) have shown that glucose stimulates the synthesis of fatty acids from acetate by rat and sheep mammary slices. confirmed their findings in mammary slices; in mammary suspension, however, these authors found glucose ineffective in promoting fatty acid synthesis although certain members of the citric acid cycle stimulated lipogenesis.…”

“…When the amount of fat in the tissue portions was small, carrier fat extracted from mammary tissue and kept in ethereal solution was added before saponification. The extraction and isolation of the fatty acids as calcium salts was carried out as described by Balmain et al (1952); when [14C]acetate was one of the substrates, the light-petroleum solution of the free fatty acids was washed with unlabelled acetate before titration with Ca(OH)2.…”

“…49,286. The Effect of Fumarate and of p-Nitrophenol on the Synthesis of Fatty Acids in Homogenates of the Mammary Gland BY C. TERNER* National Institute for Re8earch in Dairying, Univer8ity of Reading (Received 10 January 1956) In preceding papers the effects of p-nitrophenol on the oxidative metabolism of pyruvate and acetate and on oxidative phosphorylation in mammary homogenates have been described (Terner, 1954a(Terner, , 1955a(Terner, , b, 1956. These studies have now been extended to the well-known ability of mammary tissue to synthesize fatty acids, demonstrated in tissue slices by Balmain, Folley & Glascock (1952) and in cell-free preparations of mammary gland by . The latter authors found that in their preparation fatty acid synthesis was not inhibited by 2:4-dinitrophenol by more than LIPOGENESIS IN MAMMARY HOMOGENATES 30 %.…”

Effects of adrenal corticoids on fatty acid synthesis in mammary gland slices in vitro

“…A well-authenticated effect of insulin on isolated tissues in vitro is its ability to accelerate the rate of fatty acid synthesis from C2 units arising from acetate or glucose. This was first studied in rat liver slices (BlochA & Kramer, 1948;Brady & GOurin, 1950), but is particularly marked in slices of mammary gland from lactating rats (Balmain, French & Folley, 1950;Balmain & Folley, 1951; Balmain, Folley & Glascock, 1951, 1952a, 1954a), a tissue which provides an eminently useful medium for studying fatty acid synthesis in vitro. Irrespective of the mechanism by which insulin promotes fatty acid synthesis under these conditions, the antagonism of insulin and adrenal corticoids might be expected to manifest itself at some point in the pathway of fatty acid synthesis, which would imply a direct or indirect role for the adrenal cortex in the regulation of fatty acid metabolism.…”

“…Experiments on rats were carried out on abdominal mammary tissue from primiparous hooded Norway rats killed at days 11-16 oflactation. For most experiments the tissue from three rats was pooled, and slices prepared as described previously (Balmain et al 1952a). In a few experiments the tissue from individual rats was divided between treatment and control (see Table 2).…”