Introduction The percentage of angina and cardiac dysfunction and cardiovascular events increased significantly in hypertensive diabetes mellitus compared with essential hypertension and type 2 diabetes mellitus alone. Hypertension and diabetes are often associated with cardiac microvascular abnormalities. The major cardiac microcirculation alterations are the capillary rarefaction and endothelial cell functional impairment, which may be in the development of coronary insufficiency. We presume that the more serious injury in cardiac microvascular structure and function followed by hypertensive diabetes mellitus.
Aims The purpose of the present study is to investigate ultrastructural changes and expression of eNOS in rat myocardial capillary endothelial cells as a response to hypertension with diabetes mellitus.
Methods The rat model of hypertension with diabetes mellitus (SHDM) and the rat model of diabetes mellitus (DM) alone were induced by an intraperitoneal injection of streptozotocin combined with high fat diet in spontaneously hypertensive rats (SHR) and SD rats, respectively. The groups were as follows: SD, DM, SHR, and SHDM. After 16 weeks, ultrastructure of the myocardial capillaries was examined by transmission electron microscopy and the expression of endothelial nitric oxide synthase (eNOS) was detected by immunohistochemistry.
Results Ultrastructural alterations of myocardial capillaries in SHR, DM and SHDM were oedematous endothelial cell, endothelial protrusions into lumen and narrowed /or irregular lumen respectively. These alterations indicate that cell injury was more significant in the myocardium of DM and SHDM. Thickening of basal lamina in myocardial capillaries with SHR was less considerable compared with SD (31.3±4.2 nm vs 28.6±3.6 nm, p>0.05), while thickening was a prominent feature of DM (46.6±5.3) nm and SHDM (51.5±4.6) nm (compared with SD or SHR, p<0.01). The expression of eNOS in myocardial tissue was significantly lower in SHDM than in SHR or DM.
Conclusions These results suggest that a combination of hypertension and diabetes mellitus enhanced the damage of myocardial capillaries endothelial cell ultrastructure and function more than either hypertension or diabetes mellitus alone.