Enzymatic and Metabolic Adaptations in Animals

Knox, W. Eugene; Auerbach, Victor H.; Lin, E. C. C.

doi:10.1152/physrev.1956.36.2.164

Cited by 447 publications

(51 citation statements)

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“…These differences may be due to variations in enzyme activity between the sexes-a situation that has been shown to exist with other enzymes (40). Hormonal induction of enzymes has been exemplified by the demonstration of estrogen induction of certain dehydrogenases involved in steroid metabolism in the rat (41)(42)(43), as well as testosterone induction of esterase isozyme in the mouse (44).…”

Section: Discussionmentioning

confidence: 99%

Tryptophan Metabolism in Man *

Michael¹,

Drummond²,

Doeden³

et al. 1964

J. Clin. Invest.

127

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Section: Discussionmentioning

confidence: 99%

Tryptophan Metabolism in Man *

Michael¹,

Drummond²,

Doeden³

et al. 1964

J. Clin. Invest.

127

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“…were not exposed to ADH; those of patient D.K. (vasopressin-resistant diabetes insipidus) were exposed continuously to higher concentrations (4 UT per ml) than observed in normally hydrated subjects (2 KU per ml) (1) The enhanced disposal of ADH at higher plasma levels might reasonably be explained by the effect of increased amounts of substrate on the enzyme (s) systems involved in inactivation of the hormone (13). However, the mechanisms by which the state of hydration could influence hormonal turnover remain unclear.…”

Section: Discussionmentioning

confidence: 99%

The Effect of Various States of Hydration and the Plasma Concentration on the Turnover of Antidiuretic Hormone in Mammals *

Czaczkes¹,

Kleeman²,

Boston³

1964

J. Clin. Invest.

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To evaluate the rate of production and turnover of antidiuretic hormone (ADH), it is essential to know its volume of distribution. Our previous paper (1), and those in the literature (2-4), have suggested that this volume approximates the plasma volume, and most authors have explained this as the result of binding of ADH to plasma proteins. In the accompanying study (1) on the physiology of ADH in man, we were unable to demonstrate the binding of the hormone to plasma proteins using in vitro ultrafiltration and dialysis techniques. Despite this, the volume of distribution of arginine-vasopressin, calculated from the injected dose and the extrapolated zero time concentration in the plasma, was only 2.5 % of the body weight, a volume significantly less than plasma volume. We concluded, however, that under the circumstances of these experiments the volume calculated from the extrapolation technique was erroneously low. In the same study we found that the turnover rate of both endogenous and exogenous ADH (arginine-vasopressin) in humans was related to the state of hydration. Three days of dehydration significantly accelerated while a comparable period of sustained over hydration slowed the observed normal turnover rate.The present study was undertaken in an effort to determine the true volume of distribution in animals, using a constant infusion technique, and to determine whether the fractional turnover rate * Submitted for publication December' 18, 1963; ac- was truly influenced by the state of hydration per se or by the different levels of circulating ADH resulting from the various states of hydration. MethodsThe fractional turnover rate and volume of distribution of endogenous and exogenous ADH Dog experiments. 1) The disappearance curve of endogenous ADH and injected arginine-vasopressin in the water-loaded animal. Four trained female dogs were deprived of fluids for 12 hours. At the start of the experiment a sample of blood was drawn from an indwelling needle in the foreleg vein, and the animals were hydrated by stomach tube with 800 to 1,000 ml of tap water (5% of body weight). This state of hydration was maintained by a continuous iv infusion of 2.5% glucose in 0.45% sodium chloride at a rate equivalent to urine output. At suitable intervals blood samples were obtained for ADH determination. Timed urine specimens were collected by an indwelling catheter. The osmolality of the urine samples was measured by freezing point depression, using a Fiske osmometer.1 ADH was assayed by a modification of the bioassay of Heller and Stulc (1, 5). After maximal water diuresis was attained, two of the dogs were injected intravenously with 2.5 mU of synthetic arginine-vasopression,2 and its disappearance from the circulation was followed. From these data the fractional turnover rates and apparent volume of distribution were calculated.

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“…It has been shown that the organism of human beings and of animals living in nature can adapt itself to changes in the supply of certain nutrients in the diet. Evidence prov ing this fact was first furnished in the case of microorganisms [Knox el al.,1]. The first mention of the adaptation mechanisms of mammals to a change in the food supply appears in the works of Pavlov [2] and Weinland [3], who observed in the pancreas some adaptation in the secretion of the enzyme that splits up the nutrient existing in excess in the diet.…”

Section: A B Ucko and Z K Opec Technical Cooperation : A A D áMymentioning

confidence: 99%