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Biomedical subjects

B Field

Publications and source records attributed to B Field.

At least 55 records · Page 3Linked to original sources
PubMed1976

Control of rat mammary-gland pyruvate dehydrogenase by insulin and prolactin.

Withdrawal of prolactin or of insulin from the circulation of lactating rats leads, within 3h, to increased inactivation by phosphorylation of mammary-gland pyruvate dehydrogenase. Prolactin may act by priming the tissue to respond directly to normal concentrations of circulating insulin and by this means be responsible for the increased activation of the enzyme during the course of normal lactation.

Animals↗
PubMed1974

Properties of pyruvate dehydrogenase of rat mammary tissue and its changes during pregnancy, lactation and weaning.

Pyruvate dehydrogenase of rat mammary tissue showed many of the regulatory properties of the analogous enzyme in other mammalian tissues. It was inactivated in the presence of low concentrations of ATP and this rate of inactivation was slowed if pyruvate or PP(1) was also present. Reactivation by Mg(2+) in the presence of low concentrations of Ca(2+) occurred over a similar time-course. The K(m) value for Mg(2+) in this process was about 2mm. The enzyme was assayed in extracts of freeze-clamped mammary glands removed from pregnant, lactating or recently weaned rats under halothane anaesthesia. Both the initial activity and the activity after full activation (;total enzyme activity') were determined. The former parameter, when expressed on a DNA basis, varied within a range of 40 times its lowest value. Maximum total enzyme activity was about 1 unit/g wet wt. The total enzyme activity and the fraction in the active form increased in step from pregnancy to mid-lactation, remained elevated until the end of lactation and then fell steeply within 3 days after weaning. The correlation of these two parameters of enzyme activity may indicate a common regulatory factor or else an interdependence arising from inherent properties of the multi-enzyme complex.

Adenosine Triphosphate↗