Equilibrium relations between pyridine nucleotides and adenine nucleotides and their roles in the regulation of metabolic processes

Epidermal nicotinamide adenine dinucleotides in psoriasis and neurodermatitis (lichen simplex hypertrophicus)

Epidermal nicotinamide adenine dinucleotides were measured in subcorneal and basal epidermal layers in patients with psoriasis and neurodermatitis and in healthy controls. Lowry's microtechniques utilizing enzymatic cycling were used. The total NAD content in these groups was except for the involved psoriatic skin about 1.1 mmoles/kg dry weight. Between 40 and 50% of this content consisted of the reduced form. In the involved psoriatic skin the total NAD content was increased to 1.5 mmoles/kg, this increase being mainly due to a rise in NAD+. There was no difference in NAD content between epidermal layers in the various groups studied. The total NADP content was near 0.15 mmoles/kg in healthy controls and in patients with neurodermatitis. The subcorneal layers contained 10% more of the dinucleotide than the basal layers, but in the two layers the reduced form amounted to about 80% of the total. In both non-involved and involved skin of the psoriatic patients the total NADP content was significantly increased above the control level, by up to 20% in the former and up to 65% in the latter. In the two layers studied the NADP+ content was increased by about 75% in both non-involved and involved areas. In contrast, the NADPH content rose only in the basal layers of the lesion, by 55%. The increased levels of NADP+ and NADPH found in psoriasis might suggest an accelerated or differently conducted NADPH dependent biosynthesis in this disease.

Relationships between concentration of hepatic intermediary metabolites and induction of the key glycolytic enzymes in vivo

1. The time-course for the induction of hepatic glucokinase, hexokinase, phosphofructokinase, liver-type and muscle-type pyruvate kinases in reponse to various diets and insulin has been investigated over the first 48h of change in both diabetic and non-diabetic rats. 2. The results are consistent with there being separate regulatory mechanisms for the induction of each of the three key enzymes, that is for glucokinase, phosphofructokinase and liver-type pyruvate kinase. 3. To investigate the possibility that induction of these enzymes is mediated through specific metabolites a full metabolite profile has been determined under conditions identical with those in the induction experiments and the results examined for correlations between metabolite concentrations and enzyme activities. 4. Several such relationships were detected and those between glucokinase activity and the phosphorylation state of the adenine nucleotides and between liver-type pyruvate kinase activity and the concentrations of dihydroxyacetone phosphate and pyruvate are discussed in relation to the concept of inducing metabolites. 5. It is suggested that the induction of glycolytic enzymes by insulin may be secondary to the changes in the concentration of specific hepatic metabolites brought about by the acute effects of the hormone. 6. The details of the metabolite concentrations in the various experimental states have been deposited as Supplementary Publication SUP 50021 at the British Library (Lending Division) (formerly 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. (1973), 131, 5.

The development of gluconeogenesis in rat liver. Controlling factors in the newborn

1. Measurements in livers of rats delivered by Caesarian section show a rapid change in the relative proportion of adenine nucleotides. By 20min the ATP/ADP ratio had increased from 1.76 to 8.7 and the value of the relationship [ATP][AMP]/[ADP](2) increased from 1.0 to 4.4. These changes are dependent on the availability of oxygen to the animal. 2. The free [NAD(+)]/[NADH] ratio in the liver cytosol increases from 180 after delivery to reach a maximum of 1010 at 2h, before falling to 540 in the 24h-old animal. 3. The mitochondrial NAD redox potential also shows a sharp increase towards a more oxidized state in livers of delivered rats. 4. These results probably indicate that the foetal liver is hypoxic, with oxygenation occurring in the first hour after delivery. 5. Measurements in livers of naturally born rats 2min after birth also suggest that this tissue is hypoxic with an ATP/ADP ratio of 1.83 and a free [NAD(+)]/[NADH] ratio of 117. 6. Concentrations of intermediates in the gluconeogenic pathway have been determined in livers of foetal, 1h-old and 1-day-old rats. These experiments imply a facilitation of lactate dehydrogenase and glucose 6-phosphatase activities by 1h after birth, and a stimulation of phosphoenolpyruvate carboxykinase and glucose 6-phosphatase steps by 1 day after birth. 7. The appearance of gluconeogenesis in livers of newborn rats seems therefore to involve an oxygenation stage followed by an increase in phosphoenolpyruvate carboxykinase activity.