Pyridoxal-5-phosphate affects glucocorticoid receptors in intact lymphocytes similarly as in cell-free systems.
Pyridoxal-5-phosphate markedly decreased the heat-stability of the unbound thymus cytosol receptor as well as that of the receptor-[3H]-triamcinolone acetonide complex in cell-free systems. Treatment with pyridoxal phosphate also decreased DNA-binding of the complex, being present either before or after heat- and salt-activation. 5 mM pyridoxal phosphate was required for 50% inhibition of DNA-binding. Pyridoxine, at similar concentrations, had no inhibitory effect. Pre-incubation of intact thymocytes with 10 mM pyridoxine caused also a marked decrease in the binding of [3H]-triamcinolone acetonide by the cells. Treating the cells with liposomes containing 1-100 mM pyridoxal phosphate caused an increase in intracellular pyridoxal phosphate concentration by about 0.1-10 microM and a decrease in [3H]-triamcinolone acetonide binding of the cells by about 50%. The results suggest that 1. pyridoxal phosphate acts not only on the activated but also on the unbound and non-activated forms of glucocorticoid receptor in cell-free systems; 2. pyridoxal phosphate has a similar effect in the intracellular millieu and thus, 3. pyridoxal phosphate might act as a physiologic regulator of the steroid hormone action.
D000818:Animals; D002474:Cell-Free System / Q000187:drug effects; D002645:Chickens; D003600:Cytosol / Q000378:metabolism; D066298:In Vitro Techniques; D008214:Lymphocytes / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D011732:Pyridoxal Phosphate / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011965:Receptors, Glucocorticoid / Q000187:drug effects*; D011987:Receptors, Steroid / Q000187:drug effects*; D013950:Thymus Gland / Q000187:drug effects
D011965:Receptors, Glucocorticoid; D011987:Receptors, Steroid; D011732:Pyridoxal Phosphate