Calcitonin gene-related peptide dilates the pregnant rat uterine vascular bed via guanylate cyclase, ATP- and Ca-sensitive potassium channels and gap junctions.

We studied the mechanism of calcitonin gene-related peptide (CGRP)-induced vasorelaxation in isolated uterine vascular beds of pregnant rats. The vascular beds were perfused in situ with Krebs buffer containing dextran and indomethacin, an inhibitor of cyclooxygenase. Baseline perfusion pressure was maintained with norepinephrine. When applied as a bolus, CGRP caused a decreased perfusion pressure in uterine vascular beds that was dose-dependent and equal in both mid-pregnant and late-pregnant rats. The non-selective inhibitor of nitric oxide synthase (NOS), Nomega-nitro-L-arginine methyl ester (L-NAME), did not significantly affect CGRP-induced vasodilatation in vascular beds of either group. CGRP-induced vasodilatation was not influenced by preincubation with the inhibitors of adenylate cyclase (SQ 22536 or MDL 12330A), but was significantly attenuated by the selective inhibitor of soluble guanylate cyclase (ODQ). The vasorelaxant effect of CGRP was not significantly influenced by the inhibitor of voltage-gated potassium (KV) channels (4-aminopyridin), but was significantly attenuated by an inhibitor of calcium-regulated potassium (KCa) channels (tetraethylammonium) and by an inhibitor of adenosine triphosphate-sensitive potassium (KATP) channels (glibenclamide). The gap junction uncoupling agent (carbenoxolone) also significantly attenuated the CGRP-induced decrease in perfusion pressure. We conclude that vasorelaxation induced by CGRP in the pregnant rat uterine vascular bed is not dependent on endothelial nitric oxide. In the uterine circulation of late-pregnant rats, the CGRP effect involves activation of soluble guanylate cyclase, but not adenylate cyclase, and does involve KCa and KATP channels and gap junctions.

The role of endothelium-derived hyperpolarizing factor in the regulation of the uterine circulation in pregnant rats.

OBJECTIVE: The purpose of this study was to determine whether endothelium-derived hyperpolarizing factor regulates rat uterine circulation in pregnant rats. STUDY DESIGN: Intact isolated uterine vascular beds from late pregnant rats were perfused in situ with Krebs buffer that contained dextran, indomethacin, N-nitro-L-arginine methyl ester, and phenylephrine. Endothelium-derived hyperpolarizing factor-induced decreases in perfusion pressure in response to acetylcholine were analyzed. RESULTS: The decrease in perfusion pressure induced by endothelium-derived hyperpolarizing factor was significantly attenuated by 4-aminopyridine and was abolished by a combination of 4-aminopyridine and tetraethylammonium. Endothelium-derived hyperpolarizing factor-induced decrease in perfusion pressure was abolished by potassium chloride and attenuated by miconazole, but not linoleyl hydroxamic acid. Endothelium-derived hyperpolarizing factor-induced decrease in perfusion pressure persisted after perfusion with solutions that contained 2 inhibitors of nitric oxide synthase and a scavenger of nitric oxide. Nitric oxide exerted negative feedback on the endothelium-derived hyperpolarizing factor effects. CONCLUSION: In the pregnant rat uterine vascular beds, endothelium-derived hyperpolarizing factor release is activated by a delayed rectifier type of voltage-sensitive potassium channel. Endothelium-derived hyperpolarizing factor does not seem to be related to nitric oxide or to products of lipoxygenase or cytochrome p450 mono-oxygenase pathways of arachidonic acid metabolism.

Contractility of late pregnant rat myometrium is refractory to activation of soluble but not particulate guanylate cyclase.

OBJECTIVE: Our purpose was to compare the effects of agents activating particulate or soluble guanylate cyclases on the spontaneous contractile activity of the isolated pregnant rat uterus. STUDY DESIGN: Uterine rings from midpregnant (14-day) and late pregnant (21-day) rats were suspended in organ chambers to record spontaneous contractile activity. Concentration-response curves were obtained for the following natriuretic peptides: atrial, brain, and C-type; concentration-response curves were also obtained for diethylamine nitric oxide, 3-morpholino-sydnominine, and authentic nitric oxide. RESULTS: All 3 natriuretic peptides inhibited spontaneous uterine contractions equally at midgestation and late gestation. The inhibitory effects of the nitric oxide donors diethylamine nitric oxide, 3-morpholino-sydnominine, and authentic nitric oxide were attenuated in uterine tissues from animals in late stages of pregnancy. CONCLUSION: Agents activating either soluble or particulate guanylate cyclase inhibit contractions of uterine rings from midgestation rats, whereas the effects of soluble guanylate cyclase are attenuated at late pregnancy. Thus spontaneous uterine contractions are under the control of both soluble and particulate guanylate cyclases; the former is dependent on gestational age but the latter is not.

Effect of fluoxetine on contractile activity of pregnant rat uterine rings.

OBJECTIVE: We sought to compare the effects of fluoxetine, imipramine, and nortriptyline on spontaneous and serotonin-activated contractile activity of the uterine rings from midterm and term pregnant rats. STUDY DESIGN: Uterine rings from timed-pregnant Sprague-Dawley rats on day 14 (midgestation) and day 22 (term gestation) were used for isometric tension recording. Responses to cumulative concentrations of fluoxetine, imipramine, nortriptyline, and serotonin in the absence and presence of the monoamine reuptake inhibitors were studied. RESULTS: Neither of the monoamine reuptake inhibitors significantly influenced spontaneous contractile activity, whereas the concentration-dependent increase in activity induced by serotonin was inhibited in rings from both midterm and term pregnant rats. CONCLUSIONS: The reported increase in preterm delivery in women receiving fluoxetine during the third trimester cannot be explained by a direct effect on uterine contractility.

Responses of isolated perfused uterine vascular beds of nonpregnant and pregnant rats to endogenous and exogenous nitric oxide.

The responses to endothelial vasodilators and exogenous nitric oxide (NO) were characterized in intact isolated uterine vascular beds of nonpregnant, midpregnant and late-pregnant rats perfused with Kreb's buffer (37 degrees C, 5% CO(2) in air, pH approximately 7.4) containing 2% dextran and indomethacin. Phenylephrine increased perfusion pressure in the vascular beds equally in all three groups. In the presence of phenylephrine, N(omega)-nitro-L-arginine methyl ester (L-NAME) significantly augmented perfusion pressure in the order: nonpregnant

Prevention of pericyte loss by trolox in diabetic rat retina.

Prolonged hyperglycemia results in a number of diabetic complications, including retinopathy. Pericyte degeneration is one of the earliest histological changes observed in the development of diabetic retinopathy. Increased free radicals generated under hyperglycemia could damage the retina, which abounds in polyunsaturated fatty acids. In the current study, a severalfold increase in thiobarbituric acid-reactive substances was found in rat retina cultured in hyperglycemic medium, which decreased significantly when trolox, an amphipathic antioxidant, was included in the medium. To examine the contribution of oxidative stress in vivo, diabetic rats were fed trolox (0.4% in the diet) during the course of the experiments. After 5 mo of hyperglycemia, whole mounts of retinal vessels were prepared and endothelial cells (E) and pericytes (P) were counted. The ratio of E/P in the retinas obtained from normal rats, diabetic rats, and diabetic rats fed trolox were 1.74 +/- 0.186, 3.78 +/- 0.47, and 2.32 +/- 0.24, respectively. A significant restoration of pericytes by trolox suggests the involvement of oxidative injury during pericyte loss in diabetic retinopathy.

Modulation of immune responses by anabolic androgenic steroids.

Anabolic androgenic steroids (AS) have recently been placed on the Food and Drug Administration's (FDA's) list of controlled substances, because of the adverse effects seen in athletes taking accelerated dosages in attempts to enhance performance. Reported deleterious effects on abusers include sterility, gynecomastia in males, acne, balding, psychological changes, and increased risks of heart disease and liver neoplasia. Considering the roles of the immune and neuroendocrine systems and their interactions in many of these pathologies, it is important to determine the effects of these derivitized androgens on this connection. Little is known in this respect. We therefore determined the effects of anabolic steroids on certain immune responses and their effects on the extrapituitary production of corticotropin by lymphocytes. We present evidence that (1) both 17-beta and 17-alpha esterified AS, nandrolone decanoate and oxymethenelone, respectively, significantly inhibited production of antibody to sheep red blood cells in a murine abuse model; (2) the control androgens testosterone and dehydroepian-drosterone (DHEA) or sesame seed oil vehicle had no significant effects on antibody production; (3) nandrolone decanoate and oxymethenelone directly induced the production of the inflammatory cytokines IL-1 beta and TNF-alpha from human peripheral blood lymphocytes but had no effect on IL-2 or IL-10 production; (4) control androgens had no direct cytokine inducing effect; (5) nandrolone decanoate significantly inhibited IFN production in human WISH and murine L-929 cells; and (6) nandrolone decanoate significantly inhibited the production of corticotropin in human peripheral blood lymphocytes following viral infection. These data indicate that high doses of anabolic steroids can have significant effects on immune responses and extrapituitary production of corticotropin. Furthermore, the mouse model should provide an effective means by which to study other deleterious effects of anabolic steroid abuse in humans.

Effects of retinoic acid (vitamin A) on tumor necrosis factor cytolytic action.

Tumor necrosis factor (TNF) is a monokine produced primarily by macrophages. TNF has a number of activities including direct lysis of certain transformed cells and induction of antiviral activity. One of the protoypical transformed cell lines used for studying TNF cytolysis is murine L-929 cells. Because of the lysis, TNF has not been shown to have antiviral activity in these cells. Since retinoic acid (RA) induces a normal phenotype in the L-929 cells, we sought to determine if their conversion to a normal phenotype would 1) render them insensitive to the cytolytic effect and 2) allow for the development of an antiviral state. We present evidence that both the cis- and trans- forms of RA and to a lesser extent, the RA precursor beta-carotene, can inhibit recombinant human TNF cytolytic activity in mouse L-929 cells. However, blockage of the cytolytic activity does not allow development of an antiviral state.

Trolox protects hyperglycemia-induced cataractogenesis in cultured rat lens.

Hyperglycemia-induced cataractogenesis has been studied in rat lenses cultured in 50 mM glucose using an inverted microscope connected with a Universal C-mount and a CCD camera. Digital images were acquired and the opacity was determined by quantitating the transmitted light. Antioxidants, butylated hydroxy toluene (BHT) and 6-hydroxy-2,5,7,8-tetramethenyl-chroman-2-carboxylic acid (Trolox) provided good protection against 50 mM glucose-induced cataractogenesis in rat lenses for upto 8 days. Sorbitol levels in the 50 mM glucose+antioxidant groups were approximately 1.5 mM fold higher than in 50 mM glucose. The results, besides further demonstrating that oxidative damage is the major mechanism of sugar-induced cataractogenesis, show that Trolox or related amphipathic compounds could be of therapeutic use in the prevention of diabetic cataracts.

[Pathophysiological relations and clinical significance of serine protease inhibitors (serpins)]. / A szerin proteáz inhibitorok (szerpinek) kórélettani vonatkozásai és klinikai jelentösége.

Serine proteases, like all other proteases, are biologically active substances. Their effects are inhibited by serine proteases inhibitors. The disturbance of balance between protease and antiprotease leads to several diseases and to their progression. The authors give an overview on some important data on serpins (biochemical parameters, structural composition), and on the clinical considerations of some diseases that are arisen from the changes in inhibitor levels. The paper includes some own examinations, too. Finally the possibilities of prevention and therapy are discussed.