We studied the effects of hydrocortisone as a possible regulatory factor of bone blood flow and metabolism. Local bone blood flow in the tibia, distal femur, lumbar vertebra and some soft tissues (using 85Sr-microspheres), as well as 45Ca and 3H-proline incorporation into the tibia, bone density and ash weight per ml of the tibia were measured in sham-operated and oophorectomized female rats in which the influence of hydrocortisone administration (0.004 % diet for 5 weeks) was followed. Hydrocortisone markedly lowered 85Sr-microsphere uptake and blood flow through the bones of non-castrated female rats as well as elevated circulatory values in oophorectomized rats. The changes were nearly identical in the three bone samples measured; among the soft tissues only the kidneys showed a less pronounced decrease. Circulatory changes in the bones seem to be caused by local vascular reactions. Hydrocortisone also lowered the 24-hour incorporation of 45Ca and 3H-proline into the tibia of both non-castrated and oophorectomized females. In the tibia of oophorectomized rats, hydrocortisone normalized the decreased bone density and ash weight. The adrenocortical hormones are known to block eicosanoid synthesis by the inhibition of arachidonic acid production. It is possible, therefore, that local circulatory changes in the bones of rats, induced by hydrocortisone, are mediated by the changes in prostaglandin production.
An increase in bone blood flow (BBF) was observed in rats after castration whereas a decrease in BBF occurred after oestradiol or testosterone. The possible participation of prostaglandins in these changes was demonstrated. The present results show that the endothelium-derived relaxing factor, i. e. nitric oxide (EDRF-NO), might play a role in these hormonal actions on BBF. Until now, almost nothing is known about the possible action of NO on bone circulation. Methylene blue (MB) as a substance blocking EDRF-NO was administered to sham-operated or oophorectomized (OOX) female rats. We determined local blood flow (85Sr-microsphere uptake), cardiac output, blood pressure, heart rate, density of the tibia and ash weight, as well as 24-h incorporation of 45Ca and 3H-proline into the tibia. The administration of MB (0.5 % in the food for 4 weeks) significantly lowered both 85Sr- microsphere uptake and blood flow values in the tibia and distal femur of sham-operated and OOX rats. MB lowered cardiac output and blood pressure to the same extent, indicating no change in the vascular resistance. After the administration of MB (0.1 % in the food), 85Sr-microsphere uptake decreased significantly in the tibia of OOX females while no significant change was found in soft tissues. Bone density and ash weight were significantly lower in OOX rats and in sham-operated rats after MB treatment. Finally, the 24-h incorporation of both 45Ca and 3H-proline decreased significantly in OOX females after MB administration (0.04 % in the food). It can be concluded that 1) MB lowers BBF, suggesting the participation of EDRF-NO in BBF regulation, 2) MB does not influence or may even suppress cardiac output and blood pressure in high dosage, 3) MB lowers 24-hour incorporation of 45Ca and 3H-proline into the tibia of OOX rats, which is in agreement with the circulatory effect, 4) MB lowers bone density and ash weight of the tibia in non-castrated female rats. The effects of MB observed in our experiments partially differ from those of arginine-derived blocking agents. This requires further elucidation.
Using non-cholesterol sterols investigation several authors postulated a hypothesis that in the metabolic syndrome cholesterol endogenous synthesis is increased and its absorption decreased. Our study is the first attempt to evaluate the direct relation of cholesterol metabolism to the principal pathogenetic phenomenon of the metabolic syndrome – namely to insulin resistance. We have measured insulin sensitivity by two methods – Quicki (Quantitative Sensitivity Check Index) and intravenous insulin tolerance test (Kitt) and 3 indirect markers - fasting insulin level, fasting C-peptide level and SHBG (sex hormone binding globulin). The investigation was performed in three groups of subjects with a different prevalence of insulin resistance: 72 non-diabetics with ischemic heart disease, 117 young blood donors and 63 type 2 diabetics on diet therapy only. Analyzing altogether 60 relationships – between four sterols (lathosterol, squalene, sitosterol and campesterol) and five markers of insulin resistance in three groups of subjects – we have found only six significant relations between cholesterol synthesis and absorption and insulin resistance in all groups of patients. Our results indicate that there exists a significant relationship between insulin sensitivity and indices of either increased cholesterol synthesis or decreased cholesterol absorption. Insulin resistance explains only a part of both abnormalities mentioned above., A. Šmahelová, R. Hypšler, T. Haas., and Obsahuje bibliografii a bibliografické odkazy
Leptin is a 16 kDa protein hormone involved in food intake, energy expenditure regulation and numerous other physiological processes. Recently, leptin has been demonstrated to stimulate hematopoietic stem cells in vitro. The aim of our study was to measure serum leptin and erythropoietin levels in patients with sideropenic (n =18) and pernicious anemia (n=7) before and during anemia treatment. Blood samples for the blood count, leptin and erythropoietin determinations were obtained by venepunction at the time of the diagnosis of anemia and after partial and complete anemia recovery. The relationships of serum leptin levels to erythropoietin levels and blood count parameters were also studied. No significant differences in serum leptin levels between the groups studied were found. The serum leptin levels in none of groups were modified by treatment of anemia (basal levels, the levels during treatment and after anemia recovery were 13.1±14.5 vs 12.8±15.6 vs 12.0±14.8 ng/ml in patients with sideropenic anemia and 7.8±8.5 vs 9.5±10.0 vs 8.9±6.6 ng/ml in patients with pernicious anemia). The erythropoietin levels were higher at the time of anemia in both groups and decreased significantly after partial or complete recovery. Serum leptin levels in both groups correlated positively with the body mass index. No significant relationships were found between serum leptin levels and erythropoietin values or various parameters of the peripheral blood count. We conclude that serum leptin levels in patients with sideropenic and pernicious anemia positively correlate with the body mass index but are not influenced by the treatment of anemia., M. Marková, M. Haluzík, J. Svobodová, M. Rosická, J. Nedvídková, T. Haas., and Obsahuje bibliografii