CORTICOTROPIN RELEASING HORMONE (CRH) IN NORMAL AND PREGNANT UTERUS: PHYSIOLOGICAL IMPLICATIONS

4. CRH RECEPTORS

Two types of the human CRH receptor have been identified so far, probably resulting from alternative splicing of a single gene (17-19). These variants are identical except for a 29-amino acid insert present in the first intracellular loop of the type II receptor. CRH exerts its effects by binding to these plasma membrane receptors, coupled to Gs protein and adenylate cyclase. hCRH receptor type I binds to CRH with high affinity (kd:1-6.6 nM), while the signalling defect of the type II receptor (kd:18-25 nM) is due to deficient coupling to the G protein(s). The CRH receptors are widely distributed in many tissues (central and peripheral nervous system, adrenals, spleen, heart and skeletal muscle, ovary, testes and myometrium (20-26)), suggesting that hCRH may play an important role in the physiology of these organs.