Effect of adrenergic stimulation on HCO3‐ secretion in frog exocrine glands (Rana limnocharis)

The effect of adrenaline(adr) induced HCO 3 − secretion via exocrine frog skin glands was investigated. The HCO 3 − secretion was measured as the changes of short‐circuit current (Isc). The HCO 3 − secretion induced by basolateral addition of adr was related with [Ca 2+ ] i in the presence of propranolol, the inhibitor of β‐adrenoceptor, and the HCO 3 − secretion was sensitive to apical 100μM DIDS. This response induced by adr was sensitive to α‐adrenoceptor antagonist phentolamine. The adr‐stimulated HCO 3 − secretion could be reduced by Na + ‐HCO 3 − ‐cotransporter inhibitor (DIDS, 1 mM) in the basolateral solution or by carbonic anhydrase (CA) inhibitor acetazolamide. The HCO 3 − secretion induced by basolateral addition of adr was related with intracellular cAMP in the presence of phentolamine. This adr‐stimulated I sc could almost be abolished by adenylate cyclase (AC) inhibitor MDL12330A, suggesting that AC and cAMP might be involved in mediating adr‐stimulated HCO 3 − secretion across the frog skin glands, which indicated that HCO 3 − secretion induced by basolateral addition of adr might also move through CFTR. In conclusion, activation of both α‐and β‐adrenoceptors could induced Ca 2+ ‐ and cAMP‐dependent HCO 3 − secretion in frog exocrine glands.