Influence of graft innervation on neovascularization of embryonic heart tissue grafted in oculo.

We have shown that sympathetic denervation increases subendocardial capillarity during left ventricular hypertrophy. To determine the direct effects of sympathetic innervation on development of the coronary microvasculature in the absence of hemodynamic load, we grafted avascular fetal rat atrial or ventricular tissue into the anterior eye chamber of host rats which had undergone unilateral superior cervical gangliectomies. Innervation to the contralateral eye chamber remained intact. The grafts were harvested 14 or 35 days later, and volume densities of blood vessels, myocytes, and extracellular matrix were determined using standard point-counting techniques on low-power electron micrographs. Graft perfusion and metabolism were assessed simultaneously with thallium-201 and 2-[14C]deoxy-D-glucose uptake, respectively. Innervation did not significantly alter the vascular volume densities or cellular composition of atrial or ventricular tissue compared with noninnervated tissue after either 14 or 35 days in oculo. Similarly, innervation did not significantly alter graft perfusion or metabolism. We conclude that sympathetic innervation does not directly influence the growth of the microvasculature or myocardial metabolism in hemodynamically unloaded, developing heart tissue.