|Budget Amount *help
¥7,600,000 (Direct Cost : ¥7,600,000)
Fiscal Year 1995 : ¥3,100,000 (Direct Cost : ¥3,100,000)
Fiscal Year 1994 : ¥4,500,000 (Direct Cost : ¥4,500,000)
1.Analysis of endothelin receptor subtypes
To study endothelin (ET) receptor subtypes which mediate smooth muscle contraction of the rabbit and human saphenous veins, effects of some ET receptor agonists and antagonists were examined. Our results indicated pharmacological heterogeneity (ET_<A1>, ET_<A2> ; ET_<B1>, ET_<B2>) of both ET_A and ET_B recetor-mediated contractions. The currently available data, as well as those obtained in the present study, clearly indicate pharmacological heterogeneity of responses to endothelins, but they are not yet sufficient to provide conclusive evidence for endothelin receptor nomenclature. However, additional pharmacological data using ET_B-deficient mice clearly indicated that these pharmacologically heterogenous responses of ET_B receptor are completely lost, suggesting that ET_<B1> and ET_<B2> receptors are derived from a single ET_B gene.
2.Mutation analysis of endothelin B receptor in Hirschsprung disease
Hirschsprung's disease (HSCR) is characterized by the absence of autonomic ganglion cells in the terminal bowel and is a relatively common cause of intestinal obstruction in the newborn. Recently, ET_B gene has been shown as a susceptibility gene for HSCR by the production of aganglionic colon in mice with a null mutation of this gene and by demonstrating a missense mutation in a large inbred kindred with a high incidence of HSCR (Mennonite pedigree). However, no further mutations have been demonstrated in other clinical cases. We analyzed alterations of the ET_B gene in 31 isolated patients of HSCR.Three novel mutations were detected : A to T, T to C and C to A transitions at nucleotide 311,325 and 1170, respectively. These mutations resulted in Asn to Ile, Cys to Arg and Ser to Arg, predicted to produce a non-functional ET_B receptor. These observations indicate that dysfunction or loss of function of ET_B receptor may be involved in the aetiology of some isolated patients with HSCR.