Author/Editor		Sedej, Simon
Title		Vloga napetostno odvisnih kalcijevih kanalov pri sekrecijski aktivnosti v tkivnih rezinah srednjega režnja hipofize pri novorojencih in odraslih miših
Type		monografija
Place		Ljubljana
Publisher		Medicinska fakulteta
Publication year		2004
Volume		str. 80
Language		slo
Abstract		Ca2+ entry via voltage-activated Ca2+ channels (VACCs) triggers regulated exocytosis in the excitable cells. The expression of VACCs in the pituitary gland is believed to be under tight hormonal control (e.g. estrogen, GABA, dopamine; Dufy et al., 1979; Williams et al., 1989; Gomora et al., 1996, respectively). To date, most of the VACCs related studies have been performed on the enzymatically and mechanically dispersed cells (Cota and Hiriart, 1989; Keja et al., 1991; Mansvelder et al., 1996; Ciranna et al., 1996), where VACCs expression increased with time in culture (Cota, 1986). However, detailed analysis of VACCs in more in situ preparation, non-isolated cells, like pituitary tissue slices is still lacking. In our study, we aimed to determine the different types of VACCs present in the cells of the intermediate lobe (melanotrophs) in the fresh pituitary slices from newborn and adult mice and their contribution to the secretory activity. In addition, we investigated the role of 17beta-estradiol on the VACCs expression. We used whole-cell patch-clamp technique combined with the application of specific VACCs blockers. For the first time we prepared tissue slices from newborn mouse pituitary. All pharmacologically isolated VACC types contributed equally to the secretory activity (Mansvelder and Kits, 2000). However, their relative frequency varied between adults and newborns. In adults all isolated VACC types (L-, N-, P/Q-) exhibited comparable Ca2+ currents, while in newborns Ca2+ currents through L-type channels were upregulated. An exclusive expression of R-type like VACCs was found in newborns. The L-type VACC upregulation was estrogendependent and was also observed in melanotrophs from pregnant females and 17beta-estradiol-treated pituitary tissue slices from male adult mice.
Descriptors		PITUITARY GLAND CALCIUM CHANNELS CALCIUM EXOCYTOSIS ESTRADIOL CYTOSOL CELLS, CULTURED PATCH-CLAMP TECHNIQUES BARIUM NIFEDIPINE CADMIUM CHLORIDE ARTHROPOD VENOMS MICE