Endothelial cell regrowth and morphology after balloon catheter injury of alloxan-induced diabetic rabbits

Neointimal thickening after catheter injury has been reported to be influenced by the integrity of the vascular endothelium. We have previously shown that neointimal thickening is significantly reduced in alloxan-induced diabetic New Zealand White rabbits after catheter injury compared with euglycemic rabbits. In the present study, it was hypothesized that endothelial cell regrowth, morphology, and endothelium-dependent vasoreactivity after catheter injury are improved in the diabetic rabbit (glucose >/=400 mg/dl) compared with the euglycemic rabbit. Two weeks after catheter injury, the percent endothelial regrowth was significantly increased in diabetic animals compared with euglycemic animals (32.1 +/- 2 and 15.6 +/- 1, respectively; P < 0.05). The endothelial cell morphology analyzed by scanning electron microscopy was also restored 2 wk after catheter injury in thoracic aortas from the diabetic animals compared with vessels from euglycemic animals. Endothelium-dependent relaxation to ACh in vessels from diabetic and euglycemic rabbits was attenuated 2 wk after injury, and, although improved by 4 and 8 wk, relaxation remained significantly depressed. These results suggest that endothelial cell regrowth and morphology in diabetic animals was improved compared with euglycemic animals; however, endothelium-dependent vasoreactivity remained impaired. Thus the attenuated neointimal thickening seen in the diabetic rabbit may be a function of the rate and degree of regrowth rather than the normalization of ACh-induced relaxation.

Adrenomedullin Does Not Inhibit Human Platelet Aggregation

BACKGROUND: Adrenomedullin (ADM) is a hypotensive peptide isolated from human pheochromocytoma extracts discovered in 1993 using an assay system designed to monitor its ability to increase rat platelet adenosine 3',5'-cyclic monophosphate (cAMP) levels. Physiological mediators that elevate cAMP levels, such as prostaglandin (PG)E(1) and PGI(2), have also been shown to inhibit platelet aggregation. Therefore, we have chosen to investigate the effect of ADM, a peptide shown to increase platelet cAMP levels, on human platelet aggregation. METHODS AND RESULTS: Platelet-rich plasma prepared from blood donors was incubated with ADM (10(-9)-10(-6) M) for 1 min at 37 degrees C before the addition of a submaximal dose of adenosine 5'-diphosphate (ADP). ADM did not alter the platelet aggregatory response to ADP. PGE(1), a substance known to inhibit ADP-induced platelet aggregation (10(-6) M), however, inhibited ADP-induced platelet aggregation. In addition, the ADM induced a dose-dependent relation in rings of human chorionic arteries. CONCLUSIONS: These data may be interpreted to suggest that human platelets do not possess a functional ADM receptor couple with adenylate cyclase.