A single cell within a culture of freshly isolated cardiac muscle cells is injected with a fluorescent dye that cannot cross cell membranes. Within minutes, several adjacent cells became fluorescent. The most likely explanation for this observation is the presence of: (A) Gap junctions, (B) IP3 receptors, (C) Transverse tubules, (D) Desmosomes
Answer is A. Gap junctions are pores composed of paired connexons that allow the passage of ions, nucleotides, and other small molecules between cells.Ref: Guyton; 13th edition