Catecholamine neurotransmitters are synthesized by hydroxylation of tyrosine to L-dihydroxyphenylalanine (L-Dopa) by tyrosine hydroxylase (TH). The elimination of TH in both pigmented and albino mice described here, like pigmented TH-null mice reported previously (Kobayashi et al., 1995; Zhou et al., 1995), demonstrates the unequivocal requirement for catecholamines during embryonic development. Although the lack of TH is fatal, TH-null embryos can be rescued by administration of catecholamine precursors to pregnant dams. Once born, TH-null pups can survive without further treatment until weaning. Given the relatively rapid half-life of catecholamines, we expected to find none in postnatal TH-null pups. Despite the fact that the TH-null pups lack TH and have not been supplemented with catecholamine precursers, catecholamines are readily detected in our pigmented line of TH-null mice by glyoxylic acid-induced histofluorescence at postnatal day 7 (P7) and P15 and quantitatively at P15 in sympathetically innervated peripheral organs, in sympathetic ganglia, in adrenal glands, and in brains. Between 2 and 22% of wild-type catecholamine concentrations are found in these tissues in mutant pigmented mice. To ascertain the source of the catecholamine, we examined postnatal TH-null albino mice that lack tyrosinase, another enzyme that converts tyrosine to L-Dopa but does so during melanin synthesis. In contrast to the pigmented TH-null mice, catecholamine histofluorescence is undetectable in postnatal albino mutants, and the catecholamine content of TH-null pups lacking tyrosinase is 18% or less than that of TH-null mice with tyrosinase. Thus, these extraordinary circumstances reveal that tyrosinase serves as an alternative pathway to supply catecholamines.
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http://purl.uniprot.org/cit... | rdfs:comment | Catecholamine neurotransmitters are synthesized by hydroxylation of tyrosine to L-dihydroxyphenylalanine (L-Dopa) by tyrosine hydroxylase (TH). The elimination of TH in both pigmented and albino mice described here, like pigmented TH-null mice reported previously (Kobayashi et al., 1995; Zhou et al., 1995), demonstrates the unequivocal requirement for catecholamines during embryonic development. Although the lack of TH is fatal, TH-null embryos can be rescued by administration of catecholamine precursors to pregnant dams. Once born, TH-null pups can survive without further treatment until weaning. Given the relatively rapid half-life of catecholamines, we expected to find none in postnatal TH-null pups. Despite the fact that the TH-null pups lack TH and have not been supplemented with catecholamine precursers, catecholamines are readily detected in our pigmented line of TH-null mice by glyoxylic acid-induced histofluorescence at postnatal day 7 (P7) and P15 and quantitatively at P15 in sympathetically innervated peripheral organs, in sympathetic ganglia, in adrenal glands, and in brains. Between 2 and 22% of wild-type catecholamine concentrations are found in these tissues in mutant pigmented mice. To ascertain the source of the catecholamine, we examined postnatal TH-null albino mice that lack tyrosinase, another enzyme that converts tyrosine to L-Dopa but does so during melanin synthesis. In contrast to the pigmented TH-null mice, catecholamine histofluorescence is undetectable in postnatal albino mutants, and the catecholamine content of TH-null pups lacking tyrosinase is 18% or less than that of TH-null mice with tyrosinase. Thus, these extraordinary circumstances reveal that tyrosinase serves as an alternative pathway to supply catecholamines. | lld:uniprot |
http://purl.uniprot.org/cit... | skos:exactMatch | http://purl.uniprot.org/pub... | lld:uniprot |
http://purl.uniprot.org/cit... | uniprot:name | J. Neurosci. | lld:uniprot |
http://purl.uniprot.org/cit... | uniprot:author | Sasaoka T. | lld:uniprot |
http://purl.uniprot.org/cit... | uniprot:author | Roffler-Tarlov S. | lld:uniprot |
http://purl.uniprot.org/cit... | uniprot:author | Tian H. | lld:uniprot |
http://purl.uniprot.org/cit... | uniprot:author | Landis S. | lld:uniprot |
http://purl.uniprot.org/cit... | uniprot:author | Rios M. | lld:uniprot |
http://purl.uniprot.org/cit... | uniprot:author | Habecker B. | lld:uniprot |
http://purl.uniprot.org/cit... | uniprot:author | Eisenhofer G. | lld:uniprot |
http://purl.uniprot.org/cit... | uniprot:author | Chikaraishi D. | lld:uniprot |
http://purl.uniprot.org/cit... | uniprot:date | 1999 | lld:uniprot |
http://purl.uniprot.org/cit... | uniprot:pages | 3519-3526 | lld:uniprot |
http://purl.uniprot.org/cit... | uniprot:title | Catecholamine synthesis is mediated by tyrosinase in the absence of tyrosine hydroxylase. | lld:uniprot |
http://purl.uniprot.org/cit... | uniprot:volume | 19 | lld:uniprot |
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