Bicarbonate‐sensing soluble adenylyl cyclase in elasmobranch and teleost fishes

Abstract

Soluble adenylyl cyclase (sAC) is an evolutionarily conserved CO2/pH/bicarbonate sensor recently shown to be essential for blood acid/base regulation in the dogfish shark. To elucidate if sAC is present in other elasmobranchs, we performed Western blotting with round ray (Urotrygon reticulata) and leopard shark (Triakis semifasciata) samples, and found immunoractive bands of ~100 kDa in eye, rectal gland, gill, intestine and white muscle. BLAST searches revealed rainbow trout Oncorhynchus mykiss, a teleost fish, also has a sAC ortholog. By RT‐PCR, we detected sAC mRNA in trout testes, but not in other tissues. However, Western blots using anti‐trout sAC antibodies detected prominent 100 and/or 50kDa immunoreactive bands in testes, red blood cells, gill, kidney and muscle, as well as in cultured cell lines derived from gill and intestine. These results suggest sAC is present in multiple tissues from both elasmobranch and teleost fishes and that, similarly to mammals, the trout sAC gene undergoes extensive alternative splicing. This research was supported by a San Diego Fellowship to JNBR.