Cloning and distribution of the bullfrog type 1 and type 2 corticotropin-releasing factor receptors

The molecular cloning of bullfrog cDNAs encoding receptors for corticotropin-releasing factor (CRF) was undertaken as the first step in our investigation of the action of CRF at the receptor level. The specific cDNAs (630 bp) were amplified by reverse-transcribed PCR of a total RNA isolated from hypothalamus of the bullfrog, Rana catesbeiana. With the partial cDNAs as probes, two types of full-length CRF receptor cDNAs (type 1: 2275 bp, type 2: 1600 bp) were obtained from a hypothalamic cDNA library. The deduced amino acid sequences of CRF receptor types 1 (CRFR1) and CRF receptor type 2 (CRFR2) showed 79-94% and 81-92% identity with CRFR1 and CRFR2 of other vertebrates, respectively. The distribution of mRNAs of the two CRF receptors was studied by RT-PCR analysis. CRFR1 mRNA was detected almost exclusively in brain and pituitary, and to a very minor degree in testis, whereas CRFR2 was found in the peripheral tissues as well as in the brain and pituitary.