Gap junctions regulate vessel diameter in chick chorioallantoic membrane vasculature by both tone-dependent and structural mechanisms.

Objective In this study, we examined the impact of gap junction blockade on chick chorioallantoic membrane microvessels. Methods Expression of Cx37, Cx40/42, and Cx43 in chick chorioallantoic membrane tissue was studied by PCR, Western blot, and confocal immunofluorescence microscopy. Vessel diameter changes occurring under gap junction blockade with carbenoxolone (175 mu mol/L), palmitoleic acid (100 mu mol/L), (43)GAP27 (1 mmol/L) were analyzed by intravital microscopy. To analyze vascular tone, chick chorioallantoic membrane vessels were exposed to a vasodilator cocktail consisting of acetylcholine (10 mu mol/L), adenosine (100 mu mol/L), papaverine (200 mu mol/L), and sodium nitroprusside (10 mu mol/L). Results In chick chorioallantoic membrane lysates, Western blot analysis revealed the expression of Cx40 and Cx43. Immunofluorescence in intact chick chorioallantoic membrane vasculature showed only Cx43, limited to arterial vessel walls. Upon gap junction blockade (3 hours) arterial and venous diameters decreased to 0.50 +/- 0.03 and 0.36 +/- 0.06 (carbenoxolone), 0.72 +/- 0.08 and 0.63 +/- 0.15 (palmitoleic acid) and 0.77 +/- 0.004 and 0.58 +/- 0.05 (GAP27), relative to initial values. Initially, diameter decrease was dominated by increasing vascular tone. After 6 hours, however, vessel tone was reduced, suggesting structural network remodeling. Conclusions Our findings suggest a major role for connexins in mediating acute and chronic diameter changes in developing vascular networks.