Effects of Ca2+ channel blocker verapamil on tissue regeneration in a lizard tail autotomy model: a biochemical and histological study

Abstract

Abstract Ca2+ ions have been reported to augment the activities of many cell types including cellular proliferation and tissue regeneration. Moreover, it is well known that verapamil is a L-type voltage-gated Ca2+ antagonist with important clinical implications. To evaluate the role of Ca2+ ions in the regeneration of tail in lizards, verapamil was used in vivo to modulate the activity of intracellular Ca2+ in a lizard tail autotomy model. A total of 35 adult lizards were divided into three groups: lightness control group (n = 11), darkness group (n = 11) and verapamil treatment group (n = 13). The tails of adult lizards were amputated by pinching off the tail at the 15th segment from the vent to induce tail regeneration. The first two groups served as untreated constant lightness and darkness groups as controls, but the remaining group received intraperitoneally 1 mg/kg of verapamil. Following autotomy, the length of regenerating tails was measured at 10, 15, 20, 25, and 30 days post-amputation. At the end of the study, the regenerating tails from animals from each group were removed for collagen assay procedure and histological examination. We found that verapamil produced a reduction in the length of the regenerated tail compared to untreated lightness group and the percentage of tail replaced in verapamil treatment group was lower than those in lightness control group. Total collagen contents were found to be higher in lightness control group in comparison with darkness and verapamil treatment groups. Accordingly, a quantitative stereological evaluation showed a higher percentage of neural tissue and a lower percentage of connective tissue, as well as vascular tissue, in the cross-sections of the regenerated tails taken from Ca2+ channel blocker verapamil-treated lizards, as compared to other groups. In conclusion, our results suggest that verapamil influences a variety of processes including fibroblast collagen production, neurogenesis, and angiogenesis during tail regeneration in lizard, possibly due to inhibition of intracellular Ca2+ ion by verapamil.