New findings concerning the mutual action of hormones and receptors.

The actual mechanisms concerning the role of the hormone-receptor complex cannot satisfactorily explain the various hormone activities. Photobiological studies were performed in order to gain a deeper insight in this respect. 17β-estradiol (17βE(2)) was used as representative hormone and methionine-enkephaline (ME) was used as an adequate model for a receptor. Their biological behaviors and mutual interactions were investigated in air-free media (pH~7.4; 37°C) by excitation in singlet state, using monochromatic UV-light (λ=254 nm; E=4.85 eV/hη). It was found that tyrosine (Tyr) as a main component of ME, as well as ME itself, can eject solvated electrons (e(aq)(-)), when excited in singlet state. The observed quantum yields, Q (e(aq)(-)), in both cases decreased with an increase of the corresponding substrate concentration. The effect is explained by the formation of associates (unstable complexes of molecules prevailing in the ground state), which consume a proportion of the emitted e(aq)(-). The ME transients, resulting from the electron emission, can partly regenerate by electron transfer from an efficient electron donor, e.g. ascorbate. 17βE(2), like other hormones, can also eject electrons under the same experimental conditions. In a mix of 17βE(2) and ME in air-free media (40/60 water/ethanol, pH~7.4; 37°C), a mutual electron exchange takes place. Thereby 17βE(2) transients, being in status nascendy state, can partly regenerate by electron transfer from ME. Thus, the duration and action of 17βE(2) are prolonged. To our knowledge this fact is reported for the first time and it is a finding of basic biological and medical importance.