Vitamin D supplementation alleviates diabetic complications by increasing the amount of irisin in testicular tissues and blood of rats with experimental diabetes.

OBJECTIVE: Diabetes is an important endocrinological disease that has an increasing incidence in the world and affects all biological tissues including testicles. Therefore, this study aimed to reveal the histological and biochemical effects of vitamin D on irisin, apoptosis, total antioxidant status (TAS), and total oxidant status (TOS) in testicular tissues of rats with experimental diabetes. MATERIALS AND METHODS: 41 male Wistar rats, 8-10 weeks old, weighing between 200-220 g, were included in the study as the following groups: control group (n=7; no treatment), sham group [only sodium citrate buffer (SCB)] [n=7; single dose 0.1 Molar (M) SCB given intraperitoneally (i.p)], vitamin D group (n=7; 50 IU/day given orally), diabetes group [n=10; single dose 50 mg/kg Streptozotocin (STZ) dissolved in 0.1 M SCB and given i.p (tail vein blood glucose level above 250 mg/dl after 72 hours)] and diabetes+vitamin D group [n=10, single dose 50 mg/kg STZ, dissolved in 0.1 M SCB and given i.p (tail vein blood glucose level above 250 mg/dl after 72 hours) and when diabetes occurs, oral vitamin D administration of 50 IU/day)]. At the end of the 8 weeks experiment, blood was drawn from the tail vein of all rats, they were sacrificed and testicular tissues were taken. While the amount of irisin in the blood and testicular tissue supernatants was analyzed with the Enzyme-Linked Immunosorbent Assay (ELISA) method, TAS and TOS measurements were analyzed with the REL method, testicular tissues were analyzed histopathologically, immunohistochemically, and with the TUNEL method. RESULTS: When the diabetes group was compared with the control and sham groups, it was reported that the amounts of blood and tissue supernatant irisin and TAS significantly decreased and the TOS was significantly increased; a statistically significant increase in irisin and TAS of blood and tissue supernatants and a significant decrease in TOS were detected when diabetes+vitamin D and diabetes groups were compared among themselves. Similar results were obtained in the immunohistochemical studies. Tissue expressions of irisin decreased in the diabetes group compared to the control and sham groups, while the application of vitamin D increased the tissue expressions of irisin. Additionally, when the numbers of apoptotic cells were compared, it was reported that apoptotic cells in the diabetes group increased significantly compared to the control and sham groups, and vitamin D administration significantly decreased the number of apoptotic cells. CONCLUSIONS: Taken together, vitamin D administration to diabetic rats decreased the number of apoptotic cells and increased the amount of irisin. Vitamin D had an effective role in maintaining the physiological integrity of rat testicular tissues, so vitamin D may be a potent agent to be used in the treatment of diabetes in the future.

Irisin, Angtpl8, Elabela and antioxidants alteration in rats with and without energy drink and treadmill exercise.

OBJECTIVE: In this study, we sought to investigate the effects of energy drink supplementation and treadmill exercise on the levels of free radicals, antioxidants, Angtpl8, Elabela, and lipid metabolism in rats. MATERIALS AND METHODS: A total of 28 male Wistar albino rats (4 weeks old, 101.96 ± 9.75 g) were included in the study. The rats were randomly divided into four equal groups: control, exercise, supplement, and exercise+supplement groups. At the end of the study, the rats were decapitated, and blood samples were tested for levels of Angptl-8, ghrelin, leptin, irisin, SOD, CAT, TBARS, total oxidant status, and total antioxidant status using enzyme-linked immunosorbent assay. Levels of blood lipids including triglycerides, total cholesterol, HDL-C, and LDL-C were studied using spectrophotometric method in an auto analyzer. RESULTS: Statistical analysis showed statistical significance in TBARS, LDL-C, irisin, Angptl-8, and Elabela levels of the exercise group; SOD and HDL-C levels of the supplement+exercise group; and total cholesterol levels in the supplement group (p < 0.05). Although there were differences between the groups in leptin, ghrelin, and CAT levels, they were not statistically significant (p > 0.05). CONCLUSIONS: As a result, it can be argued that treadmill exercise is important in regulating lipid metabolism and stimulating peptide hormones and receptors. Furthermore, consuming energy drinks without performing exercise or physical activity increases fat stores, and such increases in the critical organs and tissues may pose a threat to the body.

Effects of carnosine on apoptosis, transient receptor potential melastatin 2, and betatrophin in rats exposed to formaldehyde.

We investigated the effects of exposure to formaldehyde on transient receptor potential melastatin 2, betatrophin, total oxidant status and total antioxidant status in rat liver and kidney tissues. We also investigated the effects of carnosine on formaldehyde treated animals. We used 28 male rats divided ramdomly into four groups of seven: untreated control group, carnosine treated group, formaldehyde treated group and formaldehyde + carnosine group. The experiment lasted for four weeks. Betatrophin levels in samples were measured uing the enzyme-linked immunosorbent assay, and total oxidant status and total antioxidant status were measured using REL assay diagnostic kits. We detected betatrophin and transient receptor potential melastatin 2 immunoreactivity using immunohistochemistry and assessed apoptosis using terminal deoxynucleotidyl transferase dUTP nick end labeling. The betatrophin and total antioxidant status levels decreased in kidney, liver and plasma following exposure to formaldehyde, while total oxidant status and terminal deoxynucleotidyl transferase dUTP nick end labeling positivity increased. Carnosine supplementation reversed histopathology and biochemical damage caused by formaldehyde. We suggest that carnosine treatment may be useful for protecting persons exposed to formaldehyde.

Weight loss at a high cost: Orlistat-induced late-onset severe kidney disease.

AIM: This report describes a case of kidney failure secondary to orlistat, a lipase inhibitor commonly used in the treatment of obesity. CASE REPORT: An 80-year-old man with type 2 diabetes who was being treated with orlistat developed rapidly progressive kidney failure. Low-grade albuminuria argued against diabetic nephropathy. Renal biopsy showed tubulointerstitial nephritis associated with numerous calcium oxalate crystals. Enteric hyperoxaluria was attributed to the orlistat treatment. The latter was stopped and the patient received calcium supplements. Six months after orlistat withdrawal, oxaluria was normalized and kidney function stabilized. CONCLUSION: Oxalate nephropathy may result from hyperoxaluria secondary to orlistat treatment. This suggests that kidney function and oxaluria be closely monitored in patients taking orlistat.

Prevention of bone loss by Panax ginseng in a rat model of inflammation-induced bone loss.

This study evaluated the protective effect of Panax Ginseng (PG) on bone metabolism in an experimental ovariectomy (OVX) model of osteoporosis in which inflammation was induced by subcutaneous magnesium silicate. The groups were: sham control (Group1, SH), sham+inflammation (Group2, SHinf), OVX (Group3), OVX+inflammation (Group4, OVXinf), OVX+inflammation+PG 100 mg/kg (Group5, OVXinf+PG1), OVX+inflammation+PG 200 mg/kg (Group6, OVXinf+PG2), OVX+PG 100 mg/kg (Group7, OVX+PG1), OVX+PG 200 mg/kg (Group8, OVX+PG1). After the OVX surgery, all the groups were allowed to recover for two months. On the 59th day after the OVX, inflammation was induced in Groups 2, 4, 5, and 6 by subcutaneous injections of magnesium silicate in the back of the animals. Groups 5 and 7 were administered oral PG 100 mg/kg, and Groups 6 and 8 were administered oral PG 200 mg/kg from the 60th to the 80th day. PG 200 mg/kg was able to restore BMD, up to values measured in both the OVX and the SH animals. The levels of OC and OP decreased in OVXinf+PG1 and OVXinf+PG2 groups. The serum levels of TNF­α, IL­1ß, and IL­6 were increased significantly in the OVXinf rats compared with the SH group. The present data showed that PG protected against in the OVX model and in inflammation-induced bone loss rat model.

Effects of atorvastatin therapy on protein oxidation and oxidative DNA damage in hypercholesterolemic rabbits.

OBJECTIVE: Our aim was to clarify the effects of hypercholesterolemic diet and administeration of atorvastatin on lipid peroxidation, protein oxidation and oxidative DNA damage in male New Zealand white rabbits. METHODS: We determined malondialdehyde (MDA), protein carbonyl (PCO) and total thiol (T-SH) levels in plasma and liver tissue, glutathione (GSH) levels in erythrocyte and liver tissue, and 8-hydroxy-2-deoxyguanosine (8-OHdG) levels in plasma. Twenty rabbits were randomly divided into two groups and fed with a high-cholesterol diet (fortified with 1% cholesterol) for 4 weeks. Such rabbits were subjected to either (Group 1) a high-cholesterol diet non-supplemented with atorvastatin (n=10) or (Group 2) a high-cholesterol diet supplemented with atorvastatin (0.3mg atorvastatin per day/kg body weight) for 4 weeks (n=10). A control group (n=5) (Group 3) was fed a cholesterol free diet for 4 weeks. Colorimetric methods were used to determine the level of the oxidative stress markers, except 8-OHdG, which was measured by ELISA. RESULTS: Rabbits were fed with the high-cholesterol diet alone (Group 1) showed higher levels of lipid profile and oxidative protein and DNA damage than compared with dose of the control group (Group 3). Atorvastatin therapy has substantially beneficial effects on oxidative protein and DNA damage in hypercholesterolemic rabbits. CONCLUSIONS: The current findings will, we hope, lead to a new insight into the pathogenesis of atherosclerosis. On the other hand inhibition of protein oxidation and DNA oxidation in the plasma by atorvastatin may be one of the pleiotropic effects of statins, and thus the underlying mechanism needs to be further clarifications.

Efficacy of supplementation of alpha-amylase-producing bacterial culture on the performance, nutrient use, and gut morphology of broiler chickens fed a corn-based diet.

A trial was conducted to evaluate the efficacy of an Escherichia coli strain producing alpha-amylase of Bacillus stearothermophilus on growth performance, nutrient use, and the morphology of the small intestine of broilers fed a corn-based diet. One hundred thirty-five 1-d-old chicks (Cobb 500) were randomly divided into 3 groups and treated as follows: (i) basal diet (control); (ii) basal diet and water supplemented with an E. coli strain that produced amylase, and (iii) basal diet and water supplemented with an E. coli strain that produced amylase plus bacterial hemoglobin. At 21 d of age, supplementation of E. coli improved daily gain (P < 0.05) and feed conversion (P < 0.01). At the end of the trial, birds supplemented with water containing bacteria consumed more and grew faster (P < 0.05) and had better feed conversion (P < 0.10) than broilers given no bacteria. Also, the presence of bacteria improved apparent digestibility of organic matter (P < 0.01). However, no effects were detected for CP or fat digestibility. Supplementation with E. coli reduced relative pancreas weight (P = 0.06) but did not affect the weight of the liver (P > 0.05) and length of duedonum, jejunum, ileum, and cecum (P > 0.05). Length of the villi and crypts were significantly increased with bacterial supplementation. Presence of the bacterial hemoglobin gene did not cause a significant difference in changes observed. The data indicated that supplementation of an E. coli strain capable of producing alpha-amylase improved digestibility of nutrients and performance of broilers fed a corn-based diet.

Effect of an aqueous distillate of Origanum onites L. on isolated rat fundus, duodenum and ileum: evidence for the role of oxygenated monoterpenes.

The aqueous distillate of Origanum onites L. (Labiatae) was reported to have various ethnomedical uses including effects on the gastrointestinal tract. The effects of three different doses (0.1, 0.2 and 0.4 mL) of the aqueous distillate of Origanum onites on isolated rat fundus, duodenum and ileum against acetylcholine induced contractions were investigated in this study. The aqueous distillate inhibited contractions in a dose dependent manner. Inhibitions were lowest on fundus. Carvacrol, being the major compound of the test substance, did not inhibit acetylcholine induced contractions of the isolated rat fundus, indicating the presence of other active principles including menthane diols. As being one of the first pharmacological studies on aqueous distillates, a possible pharmacological activity of cis-p-menth-4-ene-1,2-diol and 3,7-dimethyl-1-octen-3,7-diol is proposed in this study.

[Effect of antithrombin-III (AT-III) on intestinal epithelium changes related to obstructive icterus: experimental study in rats]. / Etude de l'effet de l'antithrombine-III (AT-III) sur les modifications de l'épithélium intestinal liées à l'ictère obstructif: étude expérimentale chez le rat.

PURPOSE: Bacterial translocation leading to sepsis is increased by obstructive jaundice(OJ). Antithrombin III (ATIII) mediates the promotion of prostaglandin release, an inhibitor of leucocyte activation and downregulator of many proinflammatory cytokines. We investigated the effect of ATIII on histopatology and villus morphology of small intestine. MATERIAL AND METHODS: We designed an experimental study with 40 rats who were divided into four groups. The first one (control, n = 10) received saline, the second (n = 10) included normal rats who received ATIII, the third group (n = 10) was rats with OJ (ligation of common bile duct), and the fourth group included OJ rats receiving AT-III. AT-III (100 UI/kg intraperitoneally) was started at the third day following bile duct ligation and repeated for 5 days. At the 8 day, rats were scarified and ileum was analysed. Histopathological assessments were performed, using a grading scheme ranging from 0 to 10 (Chui et al). RESULTS: Median histological score was found to be 2 in group 1, 1.71 in group 2, 5.43 in group 3 and 2.71 in group 4. The difference between group 3 and 4 was statistically significant. Mucosal thicknesses and villus lengths were found significantly lower in OJ group. Mucosal thicknesses and villus lengths were significantly preserved in jaundiced + AT-III group. CONCLUSION: ATIII demonstrated a salutary effect on the histopathological changes caused by the OJ and prevented the adverse effects on histopathological and morphological parameters in ileal mucosa.

Analgesic and antispasmodic activities of 2-(2-nitro-phenyl)-1H-benzimidazole 5-carboxylic acid: evidence for the importance of the 2-(o-substituted phenyl) group.

Benzimidazole 5-carboxylic acid derivatives were investigated for analgesic activity in this study. Of the benzimidazole compounds tested, 2-(2-nitro-phenyl)-1H-benzimidazole 5-carboxylic acid showed remarkable naloxone sensitive analgesic activity in the tail clamp but not in the tail immersion analgesia tests. This centrally active compound showed antispasmodic activity only on KCl induced contractions of isolated rat ileum and not on acetylcholine induced contractions. Acute toxicity of the compounds were >100 mg/kg i.p. mice. It was concluded that substitution of the 2(o-phenyl) by nitro- but not by chloro- or methoxy groups is important for naloxone sensititive analgesic activity of benzimidazole compounds and it was hypothetized that new imidazole compounds having a 2-(o-substituted phenyl) moiety needs to be investigated.

Thalamic proton magnetic resonance spectroscopy in vegetative state induced by traumatic brain injury.

OBJECTIVES: To determine whether proton magnetic resonance spectroscopy (MRS), a newer radiographic technology, would be useful in the evaluation of the thalamus of patients in vegetative states resulting from traumatic brain injury. METHODS: 14 victims of severe traumatic brain injury who were in the vegetative state and whose magnetic resonance images of the thalamus were normal underwent bilateral thalamic proton (MRS) studies. The N-acetyl aspartate to creatine (NAA:Cr) and choline to creatine (Cho:Cr) ratios were obtained for each patient. The proton thalamic MRS findings of patients who were in a persistent vegetative state (n = 8) and in patients who had regained awareness after being in the vegetative state (n = 6) were compared with proton thalamic MRS findings in five healthy volunteers. RESULTS: While conventional magnetic resonance imaging suggested that each patient had a normal thalamus, proton MRS indicated that the thalamus of each patient in the series was damaged. The NAA:Cr ratio was significantly lower in the thalami of both the patients who remained in a persistent vegetative state for the duration of the study and in those who regained awareness after being in the vegetative state (p < 0.001). In addition, NAA:Cr ratios were lower in the group of patients who remained in a persistent vegetative state than in the group of patients who regained awareness after being in the vegetative state (p < 0.001). CONCLUSIONS: Results suggest that the NAA:Cr ratio within the thalamus is significant and that thalamic MRS may be helpful when attempting to determine the degree of severity of neuronal and axonal injury in patients in the vegetative state.

Effects of dietary chromium picolinate and ascorbic acid supplementation on egg production, egg quality and some serum metabolites of laying hens reared under a low ambient temperature (6 degrees C).

This experiment was conducted to evaluate the effects of chromium (chromium picolinate, Cr Pic) and vitamin C (L-ascorbic acid) supplementation on egg production and egg quality in laying hens (Hy-Line) kept at 18 degrees C (at thermo-neutral zone) or 6 degrees C (cold stress) in temperature-controlled rooms. One hundred and fifty laying hens (32 week-old) were divided into 5 groups, 30 hens per group. The laying hens kept at 6 degrees C temperature were fed either a basal diet (low temperature-basal diet, LTB group) or the basal diet supplemented with either 400 micrograms of Cr per kg diet (Cr group), 250 mg of L-ascorbic acid per kg diet (Vit C group) or 400 micrograms of Cr plus 250 mg of L-ascorbic acid per kg diet (Vit C + Cr group) while hens kept at 18 degrees C fed a basal diet (thermo-neutral-basal diet, TNB group). Performance and egg quality were significantly reduced in LTB group compared with TNB group. Supplemental chromium and vitamin C significantly increased live weight change, egg production, and improved feed efficiency in cold-stressed hens compared with group fed the basal diet at 6 degrees C brought up to the values of the group reared under thermoneutral conditions (18 degrees C). Egg production and egg weight were also greater in each supplemental group compared with the LTB group. Separately or as a combination, supplemental chromium and vitamin C increased serum insulin but decreased corticosterone, glucose and cholesterol concentrations. Results of the present study show that supplementing vitamin C and chromium, particularly as a combination, improved the performance of cold-stressed hens. Such a combination of supplement can offer a potential protective management practice in preventing cold stress-related losses in performance of laying hens.

Analgesic activity of Nepeta italica L.

A screening study was performed on/by essential oils of Nepeta viscida Boiss and Nepeta italica L. using tail-flick and tail immersion (52.5 degrees C) methods. N. italica samples were collected from three different localities of Turkey. Surprisingly, only one of the essential oils showed significant activity, which was blocked by naloxone, indicating the involvement of opioid receptors. This was seen only with the mechanical but not the thermal algesic stimulus, suggesting a specific activity on opioid receptors, excluding mu receptors. The same, active essential oil also exhibited a non-competitive inhibition of acetylcholine contractions of isolated rat ileum but it was inactive on the isolated rat aorta. Furthermore, a correlation between the analgesic activity and the amount of 1,8-cineole was noticed.

Nepetalactone: a new opioid analgesic from Nepeta caesarea Boiss.

The essential oils of Nepeta species including Nepeta phyllochlamys P. H. Davis, N. nuda L. ssp. nuda, and N. caesarea Boiss. have been screened by use of the tail-flick and tail immersion (52.5 degrees C) methods. Of the species studied, only N. caesarea showed significant analgesic activity, besides marked sedation, which was also blocked by naloxone, indicating involvement of opioid receptors. Moreover, it was only active on mechanical, not thermal, algesic response which suggests specificity for specific opioid receptor subtypes, excluding mu-opioid receptors. Because 4a alpha,7alpha,7a alpha-nepetalactone is the main component of the essential oil of N. caesarea, and is present at very high levels (92-95%), it is concluded that 4a alpha,7alpha,7a alpha-nepetalactone is the active principle and has a specific opioid receptor subtype agonistic activity.

The effects of hyperbaric oxygen on normal and ischemic colon anastomoses.

BACKGROUND: Leakage from colonic anastomoses is a major complication causing increased mortality and morbidity, and ischemia is a well-known cause of this event. Inadequate tissue oxygenation could be reversed by using hyperbaric oxygen. This study was designed to investigate the effects of hyperbaric oxygen on the healing of ischemic and normal colon anastomoses in the rat model. METHODS: Standardized left colon resection 3 cm above the peritoneal reflection and colonic anastomosis were performed in 40 Wistar rats divided into four groups. The control group (I) received no further treatment. To mimic ischemia, 2 cm mesocolon was ligated on either site of the anastomosis in group II and IV rats. Hyperbaric oxygen therapy was started immediately after surgery in group III and IV rats (therapeutic groups). All animals were sacrificed on the fourth postoperative day. After careful relaparotomy, in situ bursting pressure was measured. The hydroxyproline contents of the anastomotic segments in equal length were determined. RESULTS: The hydroxyproline assay revealed that rats in group II with ischemic colonic anastomosis have significantly lower levels (P <0.05). The highest levels are in the group III rats with normal colonic anastomosis treated by hyperbaric oxygen (P <0.05). There was no significant difference in hydroxyproline levels between group II and group IV animals (P >0.05). Group III animals had significantly higher bursting pressures than any other group (P <0.05). Group II rats had lowest bursting pressures (P <0.05). Group IV animals had significantly higher levels than group II (P <0.05). Mean bursting pressure values both in groups III and IV and hydroxyproline levels in group III were significantly increased by hyperbaric oxygen therapy (P <0.05). CONCLUSIONS: Ischemia impairs anastomotic healing. Hyperbaric oxygen increases anastomotic healing of both normal and ischemic colonic anastomosis and reverses ischemic damage. This study demonstrated that hyperbaric oxygen improves anastomotic healing.

Acupuncture and hypnotic suggestions in the treatment of non-organic male sexual dysfunction.

We have examined the effects of acupuncture and hypnotic suggestions, and compared them with placebo in the treatment of male sexual dysfunction with no detectable organic cause. The study comprised 15 men (mean age 36.7 +/- 10.43 years) who received acupuncture treatment, 16 men (mean age 38.4 +/- 10.75 years) who underwent hypnosis (mean age 35.3 +/- 11.52 years) and 29 men (mean age 36.2 +/- 11.38 years) who served as controls. They were interviewed periodically; the patients' reports were verified by interviewing their partners. Men who received placebo had a 43-47% improvement in sexual function, while the rates of improvement in the treated groups were higher, but not significantly so. The success rates of acupuncture and hypnotic suggestions were 60% and 75% respectively. Although the improvement was not statistically significant, treatment with acupuncture could be used as an adjuvant therapy in non-organic male sexual dysfunction. The only treatment superior to placebo seemed to be hypnosis. A more effective treatment may be obtained by combining these therapeutic modalities, but this needs further study.

Efficacy of testosterone, trazodone and hypnotic suggestion in the treatment of non-organic male sexual dysfunction.

OBJECTIVE: To examine the effects of hypnotic suggestions or the administration of testosterone or trazodone to impotent men with no detectable organic cause for the impotence. PATIENTS AND METHODS: The study comprised 79 men in whom clinical and laboratory examinations revealed no organic cause for their impotence: 20 men (mean age 38.7 +/- 11.47 years) received testosterone, 21 men (mean age 39.5 +/- 10.73 years) received trazodone, 20 men (mean age 34.2 +/- 11.69 years) underwent hypnosis and 18 men (mean age 39.1 +/- 11.46 years) served as controls. They were assessed by interview 4, 6 and 8 weeks after starting treatment: the patient's reports were verified by interviewing their partners. RESULTS: Men who received a placebo had a 39% improvement in sexual function, while the rates of improvement in the treated groups were higher, but not significantly so. The success rates of testosterone and trazodone treatment and hypnotic suggestions were 60%, 67% and 80%, respectively. CONCLUSION: Although the improvement was not statistically significant, treatment with testosterone and trazodone could be used as an adjuvant therapy in nonorganic male sexual dysfunction. The only treatment superior to placebo seemed to be hypnosis. A more effective treatment may be obtained by combining these therapeutic modalities, but this needs further study.

Effects of Hypericum perforatum L. and Hypericum calycinum L. extracts on the central nervous system in mice.

Hypericum species have been used as herbal remedies for the therapy of various diseases since ancient times. It has been reported that Hypericum perforatum is a useful herbal remedy for the treatment of neurological disorders such as coxalgia, menopausal neurosis, headache, hydrophobia, hypersensitivity, mental aliments, neuralgia, paralysis, spastic paralysis, spinal convulsion, spinal irritation, stiff neck, tetanus, etc. On the basis of recent clinical studies, the extracts prepared from H. perforatum have been found to be effective for the treatment of mild and moderate depressions with no special side effects. In the present study, the effects of H. perforatum and H. calycinum on the central nervous system were investigated using various behavioural models including swimming time, locomotor activity, tail-flick and hole-board experiments. According to the results obtained, it was found that the extracts prepared from Hypericum perforatum and Hypericum calycinum are as effective as antidepressant drugs, desipramine and trimipramine, which were used for the comparison of their effects with these two plant extracts in animal models. The findings obtained also suggested that the antidepressant effect of Hypericum calycinum may be as potent as that of Hypericum perforatum and may be used for therapeutic purposes in depression.

Endothelium-dependent and independent effects of garlic on rat aorta.

Effects of garlic on isolated rat aorta were investigated by comparing with those of acetylcholine and L-arginine in the presence and absence of endothelium. For this purpose, certain linear and non-linear regression models were applied for concentration-response curves obtained by acetylcholine, L-arginine and garlic in the rat aorta. Garlic caused dose-dependent relaxations in isolated rat aorta which were attenuated by the removal of endothelium as in the case of acetylcholine. However, the relaxant responses to acetylcholine, L-arginine and garlic were not completely abolished by the endothelial denudation. Application of a number of regression models for the vasorelaxant effects of acetylcholine and garlic revealed that mechanism(s) of the effect of garlic may be different from that of acetylcholine. Furthermore, it was noted that L-arginine-induced relaxations, but not those induced by acetylcholine and garlic, are enhanced by a 2 or 4 h incubation period in the bathing medium. The findings obtained strongly suggested that the vasorelaxant effect of garlic is important in its hypotensive activity and mediated by the production of endothelium-and/or muscle-derived relaxing factors.