Avtor/Urednik		Zupančič, Gregor
Naslov		Stopnje hitre in od kalcija odvisne eksocitoze pri posameznih podganjih melanotropih v kulturi
Tip		monografija
Kraj izdaje		Ljubljana
Založnik		Medicinska fakulteta
Leto izdaje		1998
Obseg		str. 63
Jezik		slo
Abstrakt		We studied fast calcium dependent exocytosis, a basic process implicated in communication between electrically excitable cells. Such cells are nerve and endocrine cells. As a model of an electrically excitable cell, specialized in Ca2+-dependent exocytosis, melanotropes were chosen. Melanotropes are cells of intermediate pituitary that secrete peptides in a Ga2+-dependent manner. We studied the relationship between (Ga2+)i and the rate and amplitude of the Cm (membrane capacitance - a parameter linearly proportional to the cell surface area) change upon a step increase in (Ca2+)i . We used whole-cell patch-clamp combined with two phase lock-in amplifier compensated Cm measurements. This method was combined with flash photolysis of caged calcium (Ca- NP-EGTA) and fluorescent Ca2+ indicator furaptra (Ca2+)i measurements. We discovered two distinct phases of exocytotic response which we termed the fast and the slow exocytotic phase. Each one was followed by endocytosis although endocytosis following the fast phase was usually obscured by the slow phase at high changes in (Ca2+)i . Both phases were dependent on (Ga2+)i although the dependence of the fast phase was in the range below 4 micro M. The average amplitude of the fast phase in the range from 10 to 50 micro M was 151 fF coresponding to 100 - 200 granules and the average rate of change 2320 fF/s. The slow phase showed a significant sigmoidal dependence on (Ga2+)i with a Hill coefficient around 3 and EC5o around 25 micro M. The maximum amplitude obtained from the fitted sigmoid was 1310 fF at (Ca2+)i above 60 micro M and the maximum rate was 1008 fF/s. At higher (Ca2+)i a third phase could often be observed, but due to difficulties in quantization and interpretation it was not studied further. (Abstract truncated at 2000 characters)
Deskriptorji		EXOCYTOSIS CALCIUM PITUITARY GLAND MELANOPHORES RATS PATCH-CLAMP TECHNIQUES PHOTOLYSIS CELLS, CULTURED MEMBRANE POTENTIALS