3 alpha-hydroxy-5 alpha-pregnan-20-one modulation of solubilized GABA/benzodiazepine receptor complex.
The allosteric modulation of the progesterone metabolite 3 alpha- hydroxy-5 alpha-pregnan-20-one (DHP) on [3H]Flunitrazepam and [35S]t-butylbicyclophosphorothionate (TBPS) binding was investigated on a soluble receptor preparation. Better results in the solubilization occurred by the use of the zwitterionic detergent CHAPS with the inclusion of the phospholipid asolectin: this treatment was found suitable to study the steroidal modulation on [3H]Flunitrazepam and [35S]TBPS binding. We found that DHP was able to enhance [3H]Flunitrazepam binding in the presence of Cl- ions, while [35S]TBPS binding was inhibited by DHP. Scatchard analysis of specific [35S]TBPS and [3H]Flunitrazepam binding yielded in a single straight line both in the controls and in the presence of the hormone; DHP increased the apparent affinity of [3H]Flunitrazepam binding without altering the apparent Bmax value. In the case of [35S]TBPS, DHP decreased the apparent Bmax value whereas the Kd value remained nearly the same.
Istituto Policattedra di Discipline Biologiche, Università di Pisa, Italy.
L
L
Giusti
M S
MS
Belfiore
C
C
Martini
A
A
Lucacchini
D000818:Animals; D001665:Binding Sites; D001643:Bridged Bicyclo Compounds / Q000378:metabolism*; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism; D005445:Flunitrazepam / Q000378:metabolism*; D011280:Pregnanolone / Q000494:pharmacology*; D011869:Radioligand Assay; D051381:Rats; D011963:Receptors, GABA-A / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D012995:Solubility
D001643:Bridged Bicyclo Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D011963:Receptors, GABA-A; D005445:Flunitrazepam; C037476:tert-butylbicyclophosphorothionate; D011280:Pregnanolone