Leydig cell function in streptozotocin-induced diabetic rats.

Streptozotocin diabetic rats were infertile as a result of decreased Leydig cell function of the testes. The major changes found were: decreased number of Leydig cells and their spontaneous secretion of testosterone. No change in the receptors to LH on the Leydig cells was observed. LH was found to be obligatory for the regulation of Leydig cell function and fertility.     

Glucose formation from methylglyoxal in hepatocytes from streptozotocin-induced diabetic mice: the effect of insulin

Acetol and methylglyoxal are intermediates of the intrahepatic metabolism of acetone leading to pyruvate formation. In hepatocytes prepared from fasted streptozotocin-induced diabetic mice, net glucose production could be measured from methylglyoxal but not from acetone or acetol. Insulin increased glucose formation from methylglyoxal in a concentration-dependent manner, whereas it was ineffective when pyruvate was used as substrate. Drug oxidation, as evidenced byp-aminophenol formation from aniline, was enhanced by methylglyoxal, and insulin proved to be stimulatory in this case as well. It is concluded that insulin might be involved in the regulation of glucose formation from methylglyoxal, but its mode of action is not yet clear.     

C-peptide fragments stimulate glucose utilization in diabetic rats

Studies of C-peptide cellular effects show that not only the full-length native peptide but also specific C-terminal fragments are biologically active in in vitro systems. In the present study, the effect of five C-peptide fragments and the native peptide on whole-body glucose turnover was studied in streptozotocin diabetic rats using the insulin clamp technique. Insulin was infused intravenously at 18 pmol kg^–1 min^–1 for 90 min and blood glucose concentration was clamped at 8 and 4 mM in diabetic and non-diabetic animals. A steady state was reached during the last 30 min of the study period. Rat C-peptide II and fragments comprising residues 27–31 and 28–31 were effective in augmenting glucose turnover in diabetic rats (+100% to 150%), while no significant effects were seen for segments 1–26, 11–19 and 11–15. The metabolic clearance rate for glucose during infusion of C-peptide or fragments 27–31 and 28–31 in diabetic rats was similar to that seen in non-diabetic animals. We conclude that C-terminal tetra- and pentapeptides, but not fragments from the middle segment of C-peptide, are as effective as the full-length peptide in stimulating whole-body glucose turnover in diabetic rats.Received 18 December 2003; received after revision 19 January 2004; accepted 21 January 2004     

Activators of serum lipoprotein lipase in alloxan diabetic rats

Summary The amount of free fatty acid (FFA) liberated with intralipid in post-heparin guinea-pig serum, when serum from alloxan diabetic rat is incubated, is higher than that liberated when serum from healthy rats is used. The above effect is probably due to larger quantities of lipoprotein lipase present in the diabetic serum.     

Pituitary response to gonadotropin-releasing hormone in diabetic male rats

Summary The rise in serum luteinizing hormone concentration after treatment with gonadotropin-releasing hormone was less in diabetic castrated male rats than control castrates. In intact male rats, gonadotropin-releasing hormone treatment resulted in higher serum luteinizing hormone concentrations in diabetic than in control rats.Acknowledgments. This work was supported in part by a grant from the Medical Research Council of Canada. The authors are grateful to Dr G.D. Niswender, Dr L.E. Reichert, Jr. and the National Institute of Arthritis, Metabolism and Digestive Diseases, Rat Pituitary Hormone Program for providing radioimmunoassay materials. The streptozotocin was kindly provided by Dr W.E. Dulin, The Upjohn Company. D.B. Beaton and J. Brunka provided excellent technical assistance.     

Metabolic alterations in hypothalamus and limbic structures in female diabetic rats

Resumen Se determinÒ el consumo de oxÌgeno de hipotàlamo, amigdala e hipocampo en ratas hembras a las que se les habia producido una diabetes experimental por pancreatectomÌa sub-total (95%). Se usaron las ratas diabeticas durante la fase de diestro y como controles se utilizaron animales normales en distintas etapas del ciclo sexual. Los animales diabeticos en hipotàlamo presentaron valores de consumo de oxÌgeno inferiores a los màs bajos registrados en los animales controles (diestro). La amigdala, de las ratas diabeticas, mostrÒ un metabolismo oxidativo similar al presentado en estro por los controles normales, a pesar de encontrarse en la fase diestro en el momento del sacrificio. Por el contrario el consumo de oxÌgeno del hipocampo de los animales diabeticos no mostrÒ modificaciones en comparaciÒn con los controles normales.

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Supported by a grant of Fundación Marqués de Urquijo.     

Decidual cell reaction in ovariectomized-adrenalectomized rats

Enhancement of decidual cell reaction (DCR) following adrenalectomy was reversed by corticosterone as well as indomethacin. The results suggest the adrenal involvement in DCR through uterine prostaglandin production.     

Myocardial function and energy metabolism in carnitine-deficient rats

Carnitine is essential for mitochondrial metabolism of long-chain fatty acids and thus for myocardial energy production. Accordingly, carnitine deficiency can be associated with cardiomyopathy. To better understand this disease, we determined myocardial function and energy metabolism in a rat model of carnitine deficiency. Carnitine deficiency was induced by a 3- or 6-week diet containing N-trimethyl-hydrazine-3-propionate, reducing cardiac and plasma carnitine by 70-85%. Myocardial function was investigated in isolated isovolumic heart preparations. Carnitine-deficient hearts showed left ventricular systolic dysfunction, reduced contractile reserve, and a blunted frequency-force relationship independently of the substrate used (glucose or palmitate). After glycogen depletion, palmitate could not sustain myocardial function. Histology and activities of carnitine palmitoyl transferase, citrate synthase, and cytochrome c oxidase were unaltered. Thus, as little as 3-6 weeks of systemic carnitine deficiency can lead to abnormalities in myocardial function. These abnormalities are masked by endogenous glycogen and are not accompanied by structural alterations of the myocardium or by altered activities of important mitochondrial enzymes.     

Role of ascorbic acid on testicular degeneration in alloxan diabetic rats

Résumé On a observé que l'atrophie degénérative des testicules de rats atteints de diabète provoqué par l'alloxane peut être corrigée par un traitement d'acide ascorbique (vitamine C) administré en hautes doses.     

Altered K+ movement in liver mitochondria from alloxan diabetic rats

Summary Potassium movements were monitored in liver mitochondria from control and alloxan diabetic rats with a cationic electrode. There was net accumulation of K⁺ after Ca²⁺ addition to the mitochondria with the diabetic but not with the control.     

Altered K+ movement in liver mitochondria from alloxan diabetic rats

Potassium movements were monitored in liver mitochondria from control and alloxan diabetic rats with a cationic electrode. There was net accumulation of K+ after Ca2+ addition to the mitochondria with the diabetic but not with the control.