Expression of multiple adenylyl cyclase isoforms in human and dog thyroid

Although the TSH receptor and G alpha (s), which activate the cAMP cascade in the thyroid gland have been much studied, nothing is known about the ade nylyl cyclase (AC) isoforms which are actually involved in this pathway. To characterize the cAMP generation in the dog and human thyroid gland, resul ting from the presence of distinct adenylyl cyclase families, the responses to various agents (Ca2+, calmodulin (CaM), phorbol esters (TPA) and thapsi gargin (Tg)) were studied. These experiments suggest a role of at least two families of cyclases: cyclases negatively modulated by Ca2+ (ACV or ACVI) and cyclases positively modulated by PKC (ACII, ACIII or ACVII). To further analyze by other experimental procedures the expression pattern of the cyc lase isoforms in the thyroid gland, Northern blotting, Western blotting and RT-PCR experiments were performed. The results clearly suggest that in bot h species, three different adenylyl cyclases ACIII, ACVI and ACIX are mainl y expressed in thyrocytes. (C) 2000 Elsevier Science Ireland Ltd. All right s reserved.