Effects of diabetes on myocardial capillary density and serum angiogenesis biomarkers in male rats

INTRODUCTION: Cardiovascular disease is one of the main causes of mortality and morbidity in diabetic patients. This study evaluated the effects of diabetes on myocardial capillary density and several serum angiogenic factors including nitric oxide, vascular endothelial growth factor, and soluble vascular endothelial growth factor receptors. METHODS: Twelve male rats were divided into two groups: control and diabetic (n = 6 each). Diabetes was induced with a single dose of streptozotocin (50 mg/kg). After 21 days, capillary density in the myocardial tissue was evaluated using immunohistochemical staining and is reported as capillaries per mm². Blood samples were collected before and after the induction of diabetes. RESULTS: In the diabetic group, serum nitric oxide and soluble vascular endothelial growth factor receptor 2 concentrations were lower than the levels in the control group, while the level of soluble vascular endothelial growth factor receptor 1 was significantly higher. There was no significant change in the serum vascular endothelial growth factor concentration between the diabetic and control groups; however, the ratio of vascular endothelial growth factor to vascular endothelial growth factor receptor 1 was significantly lower in the diabetic animals. The myocardial capillary density was also lower in the diabetic group compared with the control group (1549 ± 161 vs. 2156 ± 202/mm², respectively). CONCLUSION: Reduced serum nitric oxide and vascular endothelial growth factor receptor 2 levels, increased serum vascular endothelial growth factor receptor 1 levels and a lower vascular endothelial growth factor to vascular endothelial growth factor receptor 1 ratio may be responsible for the decreased myocardial capillary density in diabetic rats.

The effect of chronic administration of L-arginine on the learning and memory of estradiol-treated ovariectomized rats tested in the morris water maze

OBJECTIVE: The present study was carried out to evaluate the effect of L-arginine on the learning and memory of estradiol-treated ovariectomized (OVX) rats. METHODS: Forty-eight rats were divided into six groups: (1) sham, (2) OVX, (3) sham-Est, (4) OVX-Est, (5) sham-Est-LA, and (6) OVX-Est-LA. The animals of the sham-Est and OVX-Est groups were treated by weekly injection of estradiol valerate (2mg/kg). The sham-Est-LA and OVX-Est-LA groups were treated in the same manner but with an additional daily injection of L-arginine (200mg/kg). After eight weeks, animals of all groups were tested in the Morris water maze. The escape latency and path traveled to reach the platform were compared between groups. RESULTS: Time latency and path length in the OVX group were significantly higher than in the sham group (P<0.05). The OVX-Est group had a significantly shorter traveled path length and time latency compared to the OVX group (P<0.001). Time latency and path length in the sham-Est group was significantly higher than in the sham group (P<0.001). Time latency and path length in the OVX-Est-LA group were significantly higher than in the OVX-Est group. CONCLUSIONS: These results allow us to propose that chronic treatment with estradiol enhances the spatial learning and memory of OVX rats, and that long term L-arginine treatment attenuates the effects of improvement produced by estradiol in OVX rats.