Antithrombin III prevents early pulmonary dysfunction after lung transplantation in the dog.

BACKGROUND: Ischemia-reperfusion injury with the resulting inflammatory response is a devastating complication of lung transplantation; much of the tissue damage could be diminished by control of the inflammatory response. Recent studies have show that antithrombin III (AT III) has an anti-inflammatory effect in addition to its established role in the regulation of blood coagulation. Thus, we hypothesized that the administration of AT III might help to prevent ischemia-reperfusion injury after lung transplantation. METHODS AND RESULTS: The study was performed in a dog model of orthotopic lung transplantation. Dogs were randomly assigned to receive either vehicle (controls) or AT III. We observed that in control dogs, during the 180-minute period after lung transplantation, the arterial O(2) partial pressure decreased and both the alveolar-arterial O(2) difference and the pulmonary vascular resistance increased. By contrast, these parameters remained unchanged in the group of dogs receiving AT III. Dogs with transplants receiving AT III did not show an increase in cell adhesion molecules, and histological examination revealed almost an absence of inflammatory response. The administration of AT III produced a marked increase in serum prostacyclin (PGI(2)) levels, whereas in control dogs, the PGI(2) levels did not change. The beneficial effect of AT III was not observed when dogs received indomethacin to prevent the stimulation of PGI(2) release by AT III. CONCLUSIONS: Our results demonstrate that AT III prevents ischemia-reperfusion injury in a dog model of lung transplantation and that this effect is conditioned by an increase in PGI(2) production.

A modulatory role for substance P on the regulation of luteinizing hormone secretion by cultured porcine gonadotrophs.

Substance P (SP) has been suggested to regulate gonadotroph function both directly and indirectly in different species. In pigs, the possible role of hypothalamic and pituitary SP in the control of LH release has not been examined. Here, we investigated SP effects on basal and GnRH-stimulated LH secretion by porcine gonadotrophs in vitro, in both static and dynamic culture systems. SP concentrations of 100 nM or above stimulated LH release from monolayer cultures without affecting intracellular LH content. In the same cultures, SP potentiated GnRH (10 nM)-stimulated LH release and reversed the GnRH-induced decrease of gonadotroph LH stores. The GnRH, but not the SP, effect was completely blocked by the potent GnRH-receptor antagonist antide. In superfused pituitary fragments, three successive pulses of SP or GnRH also stimulated LH release, yet the combined administration of both factors did not result in a synergistic stimulation. These results demonstrate that SP acts directly on porcine gonadotrophs to stimulate LH release, and to maintain the levels of hormonal stores, through a GnRH receptor-independent mechanism. Furthermore, our findings suggest that continuous exposure of gonadotrophs to SP would potentiate GnRH-stimulated LH secretion, thus supporting a possible role of SP as modulator of porcine gonadotroph function.

C1-esterase inhibitor prevents early pulmonary dysfunction after lung transplantation in the dog.

The success of lung transplantation to a large extent depends on effective protection of the graft from ischemic injury after reperfusion. Although mechanisms have not been clarified, the pathologic findings of ischemic injury after reperfusion are similar to adult respiratory distress syndrome, a condition in which the blood coagulation contact system is activated. This study evaluates the effect of C1-esterase inhibitor (C1-INH), the main inhibitor of the blood coagulation contact system, on short-term lung function in a dog model of orthotopic lung transplantation. Twelve lung transplantations were performed after 24 h of ischemic time. Dogs were randomly assigned to receive either vehicle (Control) or C1-INH. After the lung transplantation in the control group, Pao2 decreased by 84% and both the AaPO2 and the Qs/Qt% increased (340 and 530%, respectively, p < 0.01); these parameters remained unchanged in the C1-INH group. The hypoxemia observed in control animals was associated with decreased blood coagulation contact factors, complement consumption, increased expression of adhesion glycoproteins in leukocytes, and extensive intraalveolar and interstitial neutrophil infiltration. In contrast, C1-INH administration prevented hypoxemia, the decrease in blood coagulation contact factors, the activation of the complement system, the increase in expression of leukocyte adhesion molecules, and inflammatory cell infiltrate. This study has demonstrated that in a dog model of lung transplantation, the administration of C1-INH prevents early pulmonary dysfunction, and it suggests that activation of blood coagulation contact system and complement are important mechanisms causing ischemic injury after reperfusion.

Heterogeneity of growth hormone (GH)-producing cells in aging male rats: in vitro GH releasing activity of somatotrope subpopulations.

Studies on the age-related decline of growth hormone (GH) release have ignored that the population of GH-producing cells (somatotropes) is heterogeneous. In aging male rats, centrifugation of dispersed pituitary cells in a density gradient yields two somatotrope subpopulations, i.e. low- (LD) and high-density (HD) cells. A previous analysis of ultrastructure and GH mRNA levels has shown that storage and biosynthetic features were inversely related in both subsets. Furthermore, ultrastructural and molecular differences between LD- and HD-cells were retained throughout the rat lifespan, suggesting that the heterogeneity of somatotropes may have a biological meaning. Accordingly, the main objective of the present study was to analyze the functional heterogeneity of the somatotrope population during the aging process in male rats. For this purpose, the response of LD- and HD-somatotropes from 5-, 19-, and 26-month-old male rats was analyzed with an optimized cell immunoblot assay both under basal conditions, and after GH-releasing factor (GRF) and/or somatostatin (SS) treatments. Simultaneous measurements of hormonal release, intracellular GH content, and cell size were performed at the single-somatotrope level. Average values for those parameters were significantly higher in HD- than in corresponding LD-cells, such differences being irrespective of age or treatment. Releasing activity and GH content were significantly reduced with age in both subpopulations. GRF stimulated GH release from LD- and HD-somatotropes, and the GRF responsiveness was similar in both subpopulations and in all ages. On the other hand, SS prevented GRF-stimulated GH release in most cases. At the level of single cells, both releasing activity and cell size showed a significant, linear dependence on intracellular GH content, correlations being irrespective of age, subpopulation, or treatment. Taken together, our results demonstrate that LD- and HD-somatotrope subpopulations display quantitative differences in releasing activity that are essentially retained through aging. This functional heterogeneity is more dependent on the basal GH release of these somatotrope subsets than in their responsiveness to GRF and SS. The present findings suggest that the reduction in secretory activity at the single somatotrope level observed in both subpopulations underlies the age-related decline of pituitary GH release. Finally, a theoretical model of secretory cycle is proposed which might contribute to the understanding of the biological meaning of the somatotrope subpopulations in aging male rats.

Monounsaturated fatty acid-enriched diet decreases plasma plasminogen activator inhibitor type 1.

An increase in levels of plasma plasminogen activator inhibitor type 1 (PAI-1) is one of the main hemostatic alterations in patients with coronary heart disease. Despite growing interest in the fibrinolytic system, few studies have been undertaken to determine the effect exerted on it by the different dietary fatty acids. We investigated the effect of a monounsaturated fat (MUFA)-rich diet in comparison with a low-fat diet (National Cholesterol Education Program step 1 diet) (NCEP-1) on factors involved in blood coagulation and fibrinolysis. We also determined the effect of dietary cholesterol on these blood parameters. Twenty-one young, male, healthy volunteers followed two low-fat/high-carbohydrate diets (< 30% fat, < 10% saturated fat, 14% MUFA) for 24 days each, with 115 or 280 mg of cholesterol per 1000 kcal per day, and two oleic acid-enriched diets (38% fat, 24% MUFA) with the same dietary cholesterol as the low-fat/high-carbohydrate diets. Plasma levels of fibrinogen, thrombin-antithrombin complexes, prothrombin fragments 1+2, plasminogen, alpha 2 antiplasmin, and tissue plasminogen activator were not significantly different among the experimental diets used in this study. Consumption of the diet rich in MUFA resulted in a significant decrease in both PAI-1 plasma activity (P < .005) and antigenic PAI-1 (P < .04) compared with the carbohydrate-rich diet (NCEP-1). The addition of dietary cholesterol to each of these diets did not result in any significant additional effect. Changes in insulin levels and PAI-1 activity were positively correlated (r = .425; P < .02). In conclusion, consumption of diets rich in MUFAs decreases PAI-1 plasma activity, which is accompanied by a parallel decrease in plasma insulin levels.