In conscious dogs, phentolamine infusion significantly increased fasting portal vein insulin, glucagon, and decreased net hepatic glucose output and plasma glucose. Propranolol significantly decreased portal vein insulin, portal flow, and increased hepatic glucose production and plasma glucose. Phentolamine, propranolol, and combined blockade reduced glucose absorption after oral glucose. alpha, beta, and combined blockade abolished the augmented fractional hepatic insulin extraction after oral glucose. Despite different absolute amounts of glucose absorbed and different amounts of insulin reaching the liver, the percent of the absorbed glucose retained by the liver was similar for control and with alpha- or beta blockade, but markedly decreased with combined blockade. Our conclusions are: (a) phentolamine and propranolol effects on basal hepatic glucose production may predominantly reflect their action on insulin and glucagon secretion; (b) after oral glucose, alpha- and beta-blockers separately or combined decrease glucose release into the portal system; (c) net hepatic glucose uptake is predominantly determined by hyperglycemia but can be modulated by insulin and glucagon; (d) direct correlation does not exist between hepatic delivery and uptake of insulin and net hepatic glucose uptake; (e) alterations in oral glucose tolerance due to adrenergic blockers, beyond their effects on glucose absorption, can be, to a large extent, mediated by their effects on insulin and glucagon secretion reflecting both hepatic and peripheral glucose metabolism.
Z Chap, T Ishida, J Chou, L Michael, C Hartley, M Entman, J B Field
We have examined whether the toxic effects of homocysteine on cultured endothelial cells could result from the formation and action of hydrogen peroxide. In initial experiments with a cell-free system, micromolar amounts of copper were found to catalyze an oxygen-dependent oxidation of homocysteine. The molar ratio of homocysteine oxidized to oxygen consumed was approximately 4.0, which suggests that oxygen was reduced to water. The addition of catalase, however, decreased oxygen consumption by nearly one-half, which suggests that H2O2 was formed during the reaction. Confirming this hypothesis, H2O2 formation was detected using the horseradish peroxidase-dependent oxidation of fluorescent scopoletin. Ceruloplasmin was also found to catalyze oxidation of homocysteine and generation of H2O2 in molar amounts equivalent to copper sulfate. Finally, homocysteine oxidation was catalyzed by normal human serum in a concentration-dependent manner. Using cultured human and bovine endothelial cells, we found that homocysteine plus copper could lyse the cells in a dose-dependent manner, an effect that was completely prevented by catalase. Homocystine plus copper was not toxic to the cells. Specific injury to endothelial cells was seen only after 4 h of incubation with homocysteine plus copper. Confirming the biochemical studies, ceruloplasmin was also found to be equivalent to Cu++ in its ability to cause injury to endothelial cells in the presence of homocysteine. Since elevated levels of homocysteine have been implicated in premature development of atherosclerosis, these findings may be relevant to the mechanism of some types of chronic vascular injury.
G Starkebaum, J M Harlan
Pharmacologic doses of glucocorticoids are administered to patients with adrenal insufficiency during operative procedures to prevent hemodynamic instability, cardiovascular collapse, and death. Since these supraphysiologic doses might not be necessary and might have adverse effects, we examined the effects of different doses of glucocorticoids on hemodynamic adaptation during surgical stress in adrenalectomized primates. Sham-adrenalectomized placebo-treated animals served as controls. Adrenalectomized monkeys were maintained for 4 mo on physiologic glucocorticoid and mineralocorticoid replacement. The adrenalectomized monkeys were then stratified into three groups receiving, respectively, subphysiological (one-tenth the normal cortisol production rate), physiological, or supraphysiological (10 times the normal cortisol production rate) cortisol (hydrocortisone) treatment. 4 d later a cholecystectomy was performed. The intraoperative hemodynamic and metabolic parameters, perioperative survival rates, and postoperative wound healing were compared. The subphysiologically treated group was hemodynamically unstable before, during, and after surgery and had a significantly higher mortality rate than control. In this group, arterial blood pressure was low, and the cardiac index, systemic vascular resistance index, and left ventricular stroke work index were all reduced, suggesting decreased cardiac contractility and blood vessel tone. In contrast, the physiologically replaced group was indistinguishable from either supraphysiologically treated animals or sham-operated controls. All groups had similar metabolic profiles and normal wound healing. These findings suggest that the permissive actions of physiologic glucocorticoid replacement are both necessary and sufficient for primates to tolerate surgical stress. Supraphysiological glucocorticoid treatment has no apparent advantage during this form of stress in the primate.
R Udelsman, J Ramp, W T Gallucci, A Gordon, E Lipford, J A Norton, D L Loriaux, G P Chrousos
A new strategy was shown for the manipulation of autoantibody production in humans. Antiidiotypic antibody to human anti-DNA autoantibody was conjugated with neocarzinostatin (NCS), a cytotoxic agent, by using N-succimidyl 3-(2-pyridyldithio) propionate as a coupling agent. Human B cell clones, which produce anti-DNA autoantibodies, were killed by in vitro treatment with antiidiotype (Id)-NCS conjugates, while clones expressing an Id with irrelevant specificity were unaffected. These results indicate that treatment with anti-Id-NCS conjugates can act as a potent and specific means of generating immunosuppression of autoantibody production. This approach will have a significant advantage in aborting clones that are not effectively suppressed for the autoantibodies by anti-Id antibodies alone, and will result in a potential therapeutic treatment for systemic lupus erythematosus.
T Sasaki, T Muryoi, O Takai, E Tamate, Y Ono, Y Koide, N Ishida, K Yoshinaga
The administration of epinephrine to humans increases natural killer (NK) cell activity and numbers. If endogenous catecholamines regulate NK cells, then their activity should be increased by cocaine, an agent that potentiates endogenous catecholamines. We investigated the in vivo effect of cocaine on NK cell activity and on the distribution of lymphocyte subsets, including NK cells. Intravenous cocaine (0.6 mg/kg) produced a three- to fourfold increase in NK cell activity in peripheral blood. The increase was accompanied by a marked and selective increase in circulating NK cells, as identified by the Fc receptor (Leu-11). Normal saline and benzoylecgonine, a major metabolite of cocaine, had little effect on NK cell activity or on levels of Leu-11+ cells. Other lymphocyte subpopulations were not increased by cocaine. The time course of the alterations in NK cell numbers and activity paralleled plasma levels of cocaine. In vitro cocaine did not increase NK cell activity. Our results indicate that cocaine selectively alters the activity and distribution of the NK lymphocyte subset. Because cocaine increases the activity of endogenous catecholamines, these findings suggest that human NK cells are selectively regulated by the sympathetic nervous system.
C Van Dyke, A Stesin, R Jones, A Chuntharapai, W Seaman
Deficiency of 3-hydroxy-3-methylglutaryl-coenzyme A (CoA) lyase affects the metabolism of leucine as well as ketogenesis. This disorder is one of an increasing list of inborn errors of metabolism that presents clinically like Reye's Syndrome or nonketotic hypoglycemia. Four patients with proven 3-hydroxy-3-methylglutaryl-CoA lyase deficiency were shown to excrete a new diagnostically specific metabolite. The technique of fast atom bombardment and tandem mass spectrometry revealed that only 3-methylglutaryl-CoA is a substrate for acylcarnitine formation. Neither 3-methylglutaconyl-CoA nor 3-hydroxy-3-methylglutaryl-CoA are excreted as acylcarnitines. The excretion of 3-methylglutarylcarnitine may explain, in part, the apparent secondary carnitine deficiency in this disorder. Carnitine supplementation with moderate dietary restrictions may be a useful treatment strategy for this disorder.
C R Roe, D S Millington, D A Maltby
The kidney maintains constancy of body fluid volume by regulating urinary sodium (Na) excretion. In chronic renal failure, the reduction in glomerular filtration rate (GFR) is accompanied by an increase in Na excretion per nephron if dietary Na intake is not changed. Reduction in Na intake in proportion to reduced GFR obviates this adaptive increase in tubule Na excretion. To examine the potential role of endogenous atrial natriuretic peptide (ANP) in modulating the enhanced Na excretion per nephron in chronic renal failure, we studied rats subjected to 5/6 nephrectomy or sham operation on low, normal, and high Na intakes. Urinary Na excretion increased with increasing dietary Na in all groups, and Na excretion per nephron was increased in 5/6 nephrectomized rats as compared with sham-operated rats on the higher Na intakes. Plasma ANP levels were unaffected by dietary Na manipulations in sham-operated rats, but rose progressively in 5/6 nephrectomized rats with increasing Na intake. Despite extensive nephron reduction, however, plasma ANP levels failed to rise in uremic rats on low Na diets and in this group Na excretion per nephron also failed to rise. We conclude that enhanced ANP secretion may play an important role in promoting the adaptive increase in Na excretion per nephron in chronic renal failure. Restriction of dietary Na in the setting of reduced GFR obviates the stimulation of ANP secretion as well as the adaptive increase in Na excretion rate per nephron.
S Smith, S Anderson, B J Ballermann, B M Brenner
We report that transfusions of RT1u Wistar-Furth (WF) spleen cells prevented spontaneous diabetes in the RT1u BB/W rat while RT1b Buffalo rat spleen cells did not. In addition, donor origin WF T lymphocytes were detected in nondiabetic-susceptible BB/W recipients 5 mo after transfusion. Survival of donor-origin lymphocytes may provide the cellular mechanism by which major histocompatibility complex-compatible WF spleen cell transfusions prevent BB rat diabetes.
A A Rossini, J P Mordes, D L Greiner, K Nakano, M C Appel, E S Handler
Glutathione peroxidase (GSHPx) activity is an indicator of selenium status in selenium-deficient individuals. Utilizing polyclonal monospecific antibodies to purified erythrocyte GSHPx, we were able to determine the relationship between enzymatic activity and protein content. In erythrocytes from a selenium-deficient individual who was treated with selenium, and in HL-60 cells grown in the absence of selenium and then returned to selenium-containing medium, there was a direct relationship between enzymatic activity and protein content. Thus, selenium deficiency results not only in a decrease of GSHPx activity, but also in a decrease of GSHPx protein.
K Takahashi, P E Newburger, H J Cohen
The development of drug resistance by tumor cells is a major obstacle to the cure of human malignancy. Cyclosporin A (CsA) completely reverses primary resistance to vincristine and cross resistance to daunorubicin in a pleiotropic drug-resistant subline of human T cell acute lymphatic leukemia. This subline is over 50-fold resistant to vincristine and fivefold resistant to daunorubicin. CsA has little effect on vincristine or daunorubicin activity in drug-sensitive parental leukemia and corrects daunorubicin resistance without altering cellular daunorubicin accumulation.
L M Slater, P Sweet, M Stupecky, S Gupta