Differences in c-AMP levels in epithelial cells from pelvic and pectoral regions of the toad skin

Arginine vasopressin (AVP) stimulated active Na⁺ transport (J_Na+) and osmotic water flow J_H2O) across the pelvic skin but only (J_Na+) across the pectoral skin of the toad, Bufo woodhouseii. Isolated epithelial cells from the pelvic skin had a maximal c-AMP level of 11.16 pmoles/mg protein after 5 min of AVP treatment while that of pectoral skin was 3.64 pmoles/mg protein. The c-AMP level of both skin areas fell to unstimulated values after 20 min of AVP treatment; however, J_H2O (pelvic skin) and (J_Na+) (pelvic and pectoral skin) remained elevated during 3 hr of treatment. Dibutyryl c-AMP and theophylline stimulated J_H2O across the pelvic but not the pectoral skin. Maintaining toads in water for 12-24 hr resulted in a substantial lowering of J_H2O across the pectoral skin which was not reversible by treatment with c-AMP and theophylline.