ABSENCE OF METHYLATED THYROTROPIN-RELEASING-HORMONE IN THE BULLFROG (RANA-CATESBEIANA) BRAIN

The recent finding that [1-Me-His2]TRH is present in the carp brain pr ompted us to ascertain whether methylated TRH also exists in the frog brain. Samples were prepared from whole brain tissues of prometamorphi c and climax tadpoles, and juvenile and adult frogs by acid extraction . Each sample was subjected to reverse-phase high-performance liquid c hromatogrphy. The eluates were assayed for TRH using two kinds of anti bodies against TRH, one showing 100% cross-reactivity with both methyl ated TRHs and the other showing 3% and 43% cross-reactivities with [1- Me-His2]TRH and [3-Me-His2]TRH, respectively. Both the distribution an d amount of immunoreactive TRH in the eluates of each sample did not v ary between the assays using the two different antibodies. In both cas es, a single peak with a similar immunoreactivity appeared at a positi on similar to that of synthetic TRH. Thus, it is concluded that brains of larval and adult bullfrog contain no appreciable amount of methyla ted TRH.