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001-es BibID:	BIBFORM073602
Első szerző:	Horváth Katalin M.
Cím:	Inhibition of protein phosphatase 2A (PP2A) mimics suckling-induced sensitization of mammotropes : involvement of a pertussis toxin (PTX) sensitive G-protein and the adenylate cyclase (AC) / Katalin M. Horváth, Balázs Radnai, Tóth E. Béla, Márton I. K. Fekete, György M. Nagy
Dátum:	1999
ISSN:	0303-7207
Megjegyzések:	In lactating rats, suckling renders mammotropes more responsive to prolactin (PRL)-releasing stimuli and less responsive to PRL-inhibiting secretagogues. We have previously shown that a decrease in the activity of protein phosphatase 2A (PP2A) may be responsible for the decrease in responsiveness to the inhibitory secretagogue dopamine (DA). In our present experiments, we have studied the involvement of the adenylate cyclase (AC), stimulatory and inhibitory GTP-binding proteins and also the role of PP2A in the sensitization phenomenon. Pituitary cells obtained from mother rats separated from their pups for 4 h prior to dispersion (non-suckled), suckled for 10 or 30 min after the separation period (suckled) and without separation (continual suckling) were incubated in the presence of different doses of forskolin to activate AC and DA. In a further study, pituitary cells of non-suckled rats were pretreated with cholera toxin (CTX) or pertussis toxin (PTX) and tested for the stimulatory action of forskolin or TRH on PRL release. Ocadaic acid (OA) pretreatment has been used to investigate the involvement of PP2A. Hormone secretion was measured by the reverse hemolytic plaque assay (RHPA). Our results have shown that cells from non-suckled rats were unresponsive to forskolin. A 10-min suckling stimulus sensitizes pituitary mammotropes to respond with a PRL release to a dose-dependent activation of AC by forskolin. This sensitization of AC becomes a permanent feature of the cells when suckling continues for an additional 20 min. We have also found that pituitary mammotropes from non-suckled dams respond to forskolin or TRH with PRL release when they were preincubated with either PTX or the PP2A inhibitor OA. It clearly indicates that the non-responsive pituitary can be shifted to the responsive stage by uncoupling of inhibitory G-protein from its receptor as well as by inhibition of PP2A. This latter finding, consonant with our previous results, suggests that suckling may cause selective changes in the function of Gi of mammotropes due to a rapid phosphorylation which can remove tonic, GTP-dependent inhibitory function.
Tárgyszavak:	Orvostudományok Gyógyszerészeti tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Molecular And Cellular Endocrinology 149 : 1-2 (1999), p. 1-7. -
További szerzők:	Radnai Balázs Tóth E. Béla (1960-) (orvos) Fekete I. K. Márton Nagy György M.
Internet cím:	DOI Intézményi repozitóriumban (DEA) tárolt változat
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