Basal lamina of ovarian follicle regulates an inward Cl⁻ current in differentiated granulosa cells

Abstract

Patch-clamp experiments were conducted to study the effects of basal lamina (basement membrane) of preovulatory chicken ovarian follicle on membrane currents in differentiated chicken granulosa cells in a homologous system. The membrane capacitance (measure of total membrane area) was smaller in cells cultured on intact basal lamina than that of control cells. The granulosa cells expressed outward and two inward currents. A small fraction of the cells (3%) expressed only a transient fast-activating and -inactivating inward current carried by Ca(2+). The majority of the cells, however, expressed a slowly activating and inactivating inward current (carried by Cl(-)) that was superimposed on the transient Ca(2+) current. All cells expressed an outward current characteristic of the delayed-rectifier K(+) current. The removal of extracellular Ca(2+) led to elimination of the slow inward Cl(-) current, indicating that it is a Ca(2+)-dependent Cl(-) current. Both peak amplitude and current density of the inward Cl(-) current were significantly lower in cells cultured on freshly isolated intact basal lamina (or basal lamina stored at 4 degrees C for 12 mo) than those of control cells; however, basal lamina had no significant effect on the density of the outward current. Similar to the observations made for intact basal lamina, solubilized basal lamina suppressed the inward Cl(-) current in differentiated granulosa cells. These data show that homologous basal lamina modulates a Ca(2+)-dependent Cl(-) current in differentiated granulosa cells. These findings provide a partial explanation for the mechanisms that subserve the reported effects of basal lamina (basement membrane) on the metabolic functions of differentiated granulosa cells.

Extracellular Matrix Functions in Follicle Maturation

“…63,65 Granulosa cells isolated from chicken follicles plated on basal lamina or in the presence of solubilized basal lamina from preovulatory chicken follicles had a slower Ca 2 þ -dependent Clcurrent than those granulosa cells plated on tissue culture plastic. 66 The presence of ECM not only affects the granulosa cells but the oocyte. In the 3D mouse follicle culture system, fibronectin-, laminin-and RGD-modified alginate increase the rate at which oocytes from multilayered follicles proceeded to MII and polar body extrusion compared with unmodified alginate alone.…”

Agonist‐activated Ca2+ influx and Ca2+‐dependent Cl− channels in Xenopus ovarian follicular cells: Functional heterogeneity within the cell monolayer

“…Ca 2+ ‐dependent Cl − channel expression has been shown in several cell types (see, Hartzell et al, 2005, for an extensive review), including mammalian cumulus cells coupled with the oocyte (Arellano et al, 2002), and granulosa cells from chicken (Qin et al, 2002). Their activation participates in diverse important functions, such as secretion, signal transduction, regulation of neuronal excitability and hormone biosynthesis, or even the control of polyspermia in the Xenopus oocyte.…”

Absence of SPARC leads to impaired lens circulation

“…In vitro interactions between cells and their underlying matrix can alter the expression and function of ion channels (Asem et al, 2002; Qin et al, 2002; Smith et al, 1998; Taranta et al, 2000; Vag et al, 2007). To our knowledge these are the first experimental results demonstrating a relationship between cell-matrix interactions in the lens and the activity of ion channels and pumps that regulate solute and fluid circulation.…”