Cytosolic Cl⁻ ions in the regulation of secretory and endocytotic activity in melanotrophs from mouse pituitary tissue slices

Abstract

Cl

1α,25(OH)2-Vitamin D3 stimulation of secretion via chloride channel activation in Sertoli cells

“…Cytosolic Cl − ions enhance Ca 2+ -dependent exocytosis in a variety of endocrine cell types [47]. We have studied the effect of preincubation of TM4 cells with the voltage-gated calcium channel nifedipine (2 M), and found that this dihydropyridine antagonist abolishes 1,25(OH) 2 -D 3 stimulation of chloride currents and exocytosis (data not shown).…”

Important Contribution of α-Neurexins to Ca2+-Triggered Exocytosis of Secretory Granules

“…D, Ca 2ϩ channel subtype contributions to Ca 2ϩ currents were measured in 10 mM [Ca 2ϩ ] e by sequentially adding 1 M -conotoxin GVIA, 100 nM of -agatoxin TK plus 100 nM -conotoxin MVIIC, and 10 M nifedipine. E, The densities of Ca 2ϩ -activated Cl Ϫ currents (Turner et al, 2005) are comparable between the genotypes. F, Voltage dependence of the averaged Ca 2ϩ current densities shows a shift in ␣-neurexin double knock-out cells (arrows; ⌬V peak ).…”

“…6 D), suggesting that, in contrast to brainstem neurons (Missler et al, 2003), no functional compensation among VDCCs takes place in DKO melanotrophs. We used the peak amplitude of inward Ca 2ϩ -activated Cl Ϫ currents as an additional estimate of the amount of Ca 2ϩ entering the cytosol via VDCCs (Turner et al, 2005) and observed similar Cl Ϫ current densities in melanotrophs of both genotypes (Fig. 6 E).…”

“…Defective secretory activity from melanotrophs in adult ␣-neurexin double-mutant mice To test directly whether the hypomorphic phenotype and smaller pituitary gland lobes are a sign of insufficient endocrine release, we monitored secretion from mutant and control melanotrophs by whole-cell patch-clamp measurements of membrane capacitance in fresh pituitary gland slices as characterized before (Sedej et al, 2004Turner et al, 2005). Consistent with the morphological data reported above, the resting membrane capacitance (a parameter proportional to the membrane surface area) of adult double knock-out mice was reduced significantly as compared with wild-type and single knock-out control animals ( Fig.…”

“…For pulse generation, data acquisition, and basic analysis we used WinWCP version 3.3.9. software from J. Dempster (Strathclyde University, Glasgow, UK). High-resolution capacitance measurements (in the fF range) were made by using the compensated technique as described previously (Sedej et al, 2004Turner et al, 2005), using a sinusoidal voltage (1600 Hz; 10 mV peak-to-peak). To determine ⌬C m values, we first averaged membrane capacitance over the 30 ms preceding the depolarization to obtain a baseline value that was subtracted from the value estimated after the depolarization, averaged over a 40 ms window.…”