The expression of mRNA for voltage-dependent (K-v) and inward-rectifying K channels (K-ir) was studied in clonal rat somato-mammotroph cells (GH(3)/B-6 cells) and rat pituitary using reverse transcription-polymerase chain reaction (RT-PCR). In GH(3)/B-6 cells transcripts for 16 different K-v channel alpha-subunits (seven Shaker-related: K(v)1.2, K(v)1.4, K(v)1.5, K(v)2.1, K(v)3.2, K(v)4.1, K(v)5.1; six EAG: eag1, erg1, erg2, elk1-elk3; three KCNQ: KCNQ1-KGNQ3) and for five different K, channel alpha-subunits (K(ir)1.1, K(ir)2.3, K(ir)3.2, K(ir)3.3, K(ir)6.2) were found. In addition, transcripts for a short isoform of Kv beta 2 and transcripts for K(v)beta 3 subunits were present. In rat pituitary transcripts for 21 different K-v channel alpha-subunits (11 Shaker-related: K(v)1.3, K(v)1.4, K(v)1.6, K(v)2.1, K(v)2.2, K(v)3.2, K(v)3.4, K(v)4.1, K(v)4.2, K(v)4.3, K(v)6.1; seven EAG: eag1, ergl-erg3, elk1-elk3; three KCNQ: KCNQ1-KCNQ3) and nine K-ir channel alpha-subunits (K(ir)1.1, K(ir)2.2, K(ir)3.1-K(ir)3.4, K(ir)4.1, K(ir)6.1, K(ir)6.2) were found, In addition, all tested auxiliary subunits (K(v)beta 1-K(v)beta 3, minK, SUR1, SUR2) are expressed in the pituitary. The results indicate that the macroscopic K currents in GH(3)/B-6 and pituitary cells are presumably mediated by K channels constructed by a larger number of K channel alpha-subunits and auxiliary beta-subunits-than previously distinguished electrophysiologically and pharmacologically.
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