Fig. 4. Effects of amiloride (Am; 10^–4 mol l^–1), acetylcholine (ACh; 10^–3 mol l^–1) and ATP (10^–3 mol l^–1) on tadpole skin cultured with corticoids supplemented with growth hormone (GH; 1 µg ml^–1) plus T₃ (10^–8 mol l^–1). Open bars indicates tadpole skin cultured for 11–13 days with corticoids supplemented with GH (these values are also shown in Fig. 3A and are included here to facilitate comparison). Hatched bars indicate tadpole skin cultured for 11–13 days with corticoids supplemented with GH plus T₃. Values are means ± S.E.M. (no. of experiments is indicated in parentheses).