Extraadrenal adrenaline formation by two separate enzymes

Adrenaline (A) is synthesized in the adrenal medullae by the enzyme phenylethanolamine-N-methyltransferase (PNMT). After surgical removal of the adrenal medullae tissue A levels ranged from 22% of control in the heart to 125% of control in the liver. Use of a novel assay to measure tissue A formation revealed that many tissues can synthesize A using PNMT and another enzyme that N-methylates both noradrenaline and dopamine. These enzymes are non-neuronal, inducible and synthesize a major fraction of tissue and urine A.     

Opposite effect of PGE2 on cAMP levels in human adrenal medulla and pheochromocytoma.

PGE2 (10(-7) M) caused increased cAMP accumlation in 5 pheochromocytomas, while in 3 human adrenal medullae PGE2 caused a significant decrease of cAMP level on incubating slices in vitro. This finding is discussed in relation to the opposite effect of PGE2 on catecholamine release from human medulla and pheochromocytoma slices in vitro.     

Opposite effect of PGE2 on cAMP levels in human adrenal medulla and pheochromocytoma

Summary PGE₂ (10^–7 M) caused increased cAMP accumulation in 5 pheochromocytomas, while in 3 human adrenal medullae PGE₂ caused a significant decrease of cAMP level on incubating slices in vitro. This finding is discussed in relation to the opposite effect of PGE₂ on catecholamine release from human medulla and pheochromocytoma slices in vitro.Acknowledgment. This paper is part of a Ph. D. thesis of Punya Boonyaviroj.Established Investigator of the Chief Scientist's Bureau, Israeli Ministry of Health.     

Inhibition of aldosterone synthesis induced by flow-stop in the Mongolian gerbil adrenal gland superfused in vitro

Stopping of superfusion flow for short periods resulted in a significant accumulation of aldosterone within the Mongolian gerbil adrenal gland superfused in vitro. Aldosterone amounts in the first 2-min samples after the re-starting of superfusion were positively correlated with the length of flow-stop; however, they were significantly lower than calculated amounts: 5-min stop: 37 +/- 1% inhibition, 10-min stop: 51 +/- 1% inhibition. In addition, aldosterone secretion was significantly suppressed during prolonged incubation. The results suggest that aldosterone and glucocorticosteroid amounts in adrenal tissue may modulate basal corticosteroidogenesis and that self-suppression forms an important part of the control mechanisms involved in corticosteroidogenesis.     

Glutathione-related enzyme activities in pregnant rat liver

The levels of GSH-related enzyme activities during pregnancy were determined. A significant increase in Selenium-dependent GSH peroxidase and GSH S-transferase E activity was observed. A concomitant increase in gamma-glutamylcysteine synthetase was measured, which indicated an increased ability to synthesize the tripeptide.     

Effects of ACTH and diabetes on phospholipid metabolism in adrenal mitochondria.

Incorporation of 32P into adrenal mitochondrial phospholipids (PL) incrased in ACTH-treated rats, but it decreased in diabetics, inspite of the fact that these animals showed adrenal overacity. Since diabetics did not show increased 11 beta-hydroxylation. as opposed to ACTH-treated rats, it is suggested that the stimulation of this enzyme activity by exogenous ACTH is related to an increased turnover of PL at the mitochondrial membrane. The process is impaired in diabetics and prevents the stimulation of 11 beta-hydroxylation.     

Higher oxygen affinity of sheep Hb C compared to Hb A and Hb B

Summary Sheep which have Hb A, synthesize the perinatal Hb C in response to severe tissue hypoxia. It is known that Hb A displays a higher oxygen affinity than Hb B. The results of this study indicate that Hb C exhibits an oxygen affinity and a Bohr effect higher than those of Hb A and Hb B.Part of this work was supported by a grant of Ministero Pubblica Istruzione.     

Cellular changes of adrenal under the acute stress of O-chlorobenzylidene malononitrile (CS).

This investigation describes histological and cytometrical changes of cortical and medullary tissue of adrenal in rats under the acute stress of O-chlorobenzylidene malononitrile (10 mg/kg and 20 mg/kg). It has been observed that after injection of CS, the adrenal gland showed histological changes both in the cortical and medullary region.     

Primitive actimoterigian fishes can synthesize ascorbic acid

Amphibians and reptiles evolved with the capacity to synthesize ascorbic acid. Some higher vertebrates, like bats, guinea pigs, primates, and humans have lost the microsomal enzyme gulonolactone oxidase, and in cases of ascorbic acid deficiency suffer from symptoms of scurvy. The question of whether the capacity to synthesize ascorbate is also present in lower vertebrates could throw light on the evolution of this pathway. In order to find out whether ascorbic acid synthesis took place in two primitive Actinopterigian fish, the paddlefish (Polydon spathula) and the white sturgeon (Acipenser transmontanus) were fed with a scorbutogenic diet or diet(s) supplemented with a graded level of ascorbic acid. We found no growth depression nor external symptoms of scurvy, which would be pronounced in modern bony fishes (Teleostei) under similar conditions. The tissue level of ascorbate in both these primitive species indicated that vitamin C in intestine and liver is not depleted when fed a scorbutogenic diet. Gulonolactone oxidase activity was found in the kineys of the Actinopterigian fishes. Thus, I question the accepted evolutionary pathway for ascorbic acid biosynthesis in lower vertebrates and suggest that the modern bony fishes,Teleostei, lost their ability to express the gulonolactone oxidase genes after they had separated during the Silurian from their common ancestor with the coelacanths (Latimeria) and Dipnoi.     

Glutathione-related enzyme activities in pregnant rat liver

Summary The levels of GSH-related enzyme activities during pregnancy were determined. A significant increase in Selenium-dependent GSH peroxidase and GSH S-transferase E activity was observed. A concomitant increase in -glutamylcysteine synthetase was measured, which indicated an increased ability to synthesize the tripeptide.     

Pseudocholinesterase in obesity: Hypercaloric diet induced changes in experimental obese mice

Summary Pseudocholinesterase activity is significantly higher in liver and serum, but lower in adipose tissue of genetically obese, diabetic and gold thioglucose treated mice. Similar enzyme changes were also observed in lean mice on a high carbohydrate diet. A marked reduction (40%) in PChE activity occurred in the liver of genetically diabetic mice when starved for 24 h. These observations suggest that pseudocholinesterase induction in the liver and repression in the adipose tissue is affected by excessive calorie intake in obesity. This provides a model to study the biological function of PChE in health and disease.Acknowledgments. We thank Dr Charles A. Janeway Child Health Centre and Faculty of Medicine, Memorial University of Newfoundland for financial support.     

Selective activation of noradrenergic neurons in the brainstem and spinal cord of young spontaneously hypertensive rats

Summary In young spontaneously hypertensive rats (SHR), dopamine -hydroxylase (DBH) and phenylethanolamine N-methyltransferase (PNMT) activities were examined in the brainstem nuclei. Activation of noradrenergic neurons in the locus coeruleus, A2 and spinal intermediolateral cell areas, resulting in enhanced sympathetic nervous activity in the periphery, initiates hypertension. Adrenergic neurons, unchanged in these and A1 cell areas of young SHR, are not involved in the development of hypertension in SHR.     

Hypoaldosteronism in piglets induced by carbadox

An exploratory study was made of the mechanisms underlying the toxic action of carbadox in young pigs: dehydration, loss of appetite and at autopsy seemingly specific and selective structural alterations of the glomerular zone of the adrenal cortex. Administration of carbadox in the feed, in dosages of 150 ppm (approximately 6 mg X kg-1 b. wt X day-1) caused a rapid decline in the plasma aldosterone levels (to 10% of control) followed by significant changes in the sodium and potassium levels in blood. Characteristic for the toxic action of carbadox are the rapid and seemingly selective and specific alterations in the aldosterone-releasing zona glomerulosa of the adrenals. Our results indicate that with carbadox a functional and possibly reversible extirpation of the adrenal zona glomerulosa can be achieved in pigs.     

Tissue specificity of testosterone fixation: demonstrated by ultrastructural immunocytochemistry after cryoultramicrotomy]

Testosterone can be detected by immunocytochemistry on ultrathin slices obtained by cryoultramicrotomy. Testosterone detected by this method is likely bound on a binding site having a high affinity. In order to study the tissue specificity of this binding, testosterone was tested in Rat pituitary gland, liver and adrenal glands. Immunoreactive testosterone was detected in the gonadotropic cells of the pituitary gland, in the hepatocytes. Testosterone was not detected by immunocytochemistry in the pituitary cells other than the gonadotropic cells and in the cells of the medulla of adrenal glands. These data testify in favour of tissue specificity of the testosterone binding.     

Cellular changes of adrenal under the acute stress of O-chlorobenzylidene malononitrile (CS)

Summary This investigation describes histological and cytometrical changes of cortical and medullary tissue of adrenal in rats under the acute stress of O-chlorobenzylidene malononitrile (10 mg/kg and 20 mg/kg). It has been observed that after injection of CS, the adrenal gland showed histological changes both in the cortical and medullary region.The authors are thankful to Dr. P.K. Ramachandran, Director, Defence Research and Development Establishment, Gwalior, for his sustained interest and critical suggestions in the course of this study.     

Effect of stress on choline acetyltransferase activity of the brain and the adrenal of the rat

Choline acetyltransferase (ChAT) activity was determined in cerebral cortex, hypothalamus, hippocampus, cerebellum, medulla oblongata, midbrain and adrenal gland of rats exposed to acute or chronic stress. The exposure of animals to acute immobilization and cold stress (4°C) for one hour resulted in a significant decline of ChAT activity in all brain regions examined except for the medulla oblongata. Moreover, the exposure to acute stress resulted in significant increase of the same enzyme in the adrenal gland. However, chronic exposure of animals to cold stress (4°C) for 7 days resulted in no significant changes of ChAT activity in all tissues examined except for a decline in the midbrain and an increase in the medulla oblongata. The administration of corticosterone (2.0 mg/kg) 1 h prior to sacrificing caused an effect similar to that of acute stress on ChAT activity in all brain regions except for the hypothalamus and the cerebellum. It was concluded from this experiment that stress-induced changes in the ChAT activity of specific brain regions might be mediated by the adrenal steroids.This work was supported by a grant from the National Aeronautics and Space Administration (NSG 2183 and NAG 2-411), a grant from the National Institutes of Health (NIH RR 0811) and a grant from the Division of Research Resources (NIH grant RR 03020).     

Suppressed collagenolytic activity in polymorphonuclear leucocytes from diabetic humans

Summary Extracts of polymorphonuclear leucocytes (PMNL) from diabetic human exhibited less collagenolytic activity than extracts from normoglycemic control subjects. Partially purified control extracts produced ^A and ^B collagen breakdown products of the type generated by mammalian collagenase; the diabetic preparation produced decreased amounts of the same products. The diabetic PMNLs may synthesize abnormally low levels of collagenase or contain inactive forms of this enzyme.Supported by a grant (No. DE-03987) from the National Institute of Dental Research (N.I.H.), USA. This study forms part of the Ph.D. thesis of G.A. Nicoll.Acknowledgments. The authors wish to thank Ms Salema Karim and Mr F.R. Singh for excellent technical assistance.     

Molecular forms of dopamine beta-hydroxylase in rat superior cervical ganglion and adrenal gland

Summary Dopamine beta-hydroxylase (DBH) enzyme activity was associated in rat superior cervical ganglion with tetrameric DBH-A (294,000 D) and dimeric DBH-B (147,000 D) and in rat adrenal gland with DBH-A and a novel molecular form of DBH, defined as DBH-C, with a molecular weight of 125,000 D. Pretreatment of the rats with cycloheximide markedly reduced DBH activity without altering the molecular heterogeneity.     

Molecular forms of dopamine beta-hydroxylase in rat superior cervical ganglion and adrenal gland

Dopamine beta-hydroxylase (DBH) enzyme activity was associated in rat superior cervical ganglion with tetrameric DBH-A (294,000 D) and dimeric DBH-B (147,000 D) and in rat adrenal gland with DBH-A and a novel molecular form of DBH, defined as DBH-C, with a molecular weight of 125,000 D. Pretreatment of the rats with cycloheximide markedly reduced DBH activity without altering the molecular heterogeneity.     

Effects of ACTH and diabetes on phospholipid metabolism in adrenal mitochondria

Summary Incorporation of 32P into adrenal mitochondrial phospholipids (PL) increased in ACTH-treated rats, but it decreased in diabetics, inspite of the fact that these animals showed adrenal overactivity. Since diabetics did not show increased 11 -hydroxylation, as opposed to ACTH-treated rats, it is suggested that the stimulation of this enzyme activity by exogenous ACTH is related to an increased turnover of PL at the mitochondrial membrane. This process is impaired in diabetics and prevents the stimulation of 11 -hydroxylation.