No abstract

GH3 cells which had been exposed for 30 min to [³H]-TRH and had performed their maximum biological response, i.e. increase of prolactin (PRL) release, retained intracellular radioactivity which consisted of chemically unmodified TRH (>93%). Such preloaded GH3 cells were found able to spontaneously release into the culture medium a radioactive material [³H]-RM) which was analyzed. The kinetics of binding of [³H]-RM to intact GH3 cells and competition with unlabeled TRH were indistinguishable from [³H]-TRH. [³H]-RM was able to stimulate PRL release from GH3 cells. In addition thin layer electrophoresis (TLE) revealed that 90% of [³H]-RM migrated like TRH reference. All these features strongly suggest that [³H]-RM is identical to [³H]-TRH.

No abstract

Aus dem Azlacton (I) erhält man in bekannter Weise das ungesättigte geschützte Dipeptid (II), dessen Hydrierung zu (III) in Gegenwart zahlreicher Rhodium‐Katalysatoren wie (IV), vor allem aber in Gegenwart optisch aktiver Komplexbildner untersucht wird.

Specific methods of tritium labelling onto C‐2 and (or) C‐5 positions of the imidazole ring were successfully applied to thyroliberin (TRF, L‐Glu‐L‐His‐L‐Pro‐NH2). Diazocoupling by diazotized sulphanilic acid and iodination by iodine monochloride of the histidyl residue were chosen to prepare precursors and to quantify the distribution of tritium atoms which were introduced. Catalytic hydrogenolysis in the presence of tritium gas of 5‐iodohistidine2 ‐ and 2(4‐sulfophenylazo)histidine2 ‐ derivatives allowed to label these positions with specific radioactivities of 30 Ci and 25 Ci/mmole respectively. For comparison thyroliberin tritiated by direct catalytic exchange is labelled essentially onto C‐2 with a specific radioactivity of 30 Ci/mmole.