The combined effect of intraperitoneal insulin injection and electrical stimulation on hind limb regeneration in a metamorphic stage (number 58) of the Egyptian toad, Bufo regularis Reuss was studied after amputation at the mid shank. Insulin injection associated with electrical stimulation was an enhancing factor that promotes limb regeneration. Application of insulin with 10 mA current was more effective than that with 5 mA and 3 mA currents. Insulin and 10 mA current decreased the negative cases which failed to regenerate to 2.96%, while insulin and 5 mA current decreased them to 22.73%. Insulin with 3 mA current resulted in the production of 50% negative cases compared with 34% in control. It was suggested that insulin may enhance limb regeneration either by its direct effect on nerve endings, through its action on insulin and/or insulin like growth factors receptors or by increasing protein kinase activity resulting in increasing blastemal cell proliferation rate.
Electrical current was suggested to enhance limb regeneration either directly or indirectly through increasing the efficiency of insulin in promoting cell proliferation and limb regeneration. It was concluded that application of combined effect of insulin injection and electrical stimulation in highly affecting limb regeneration in Bufo regularis Reuss rather that application of either stimuli alone.