Regulated anion secretion in cultured epithelia from Sertoli cells of immature rats

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Abstract
Cultured epithelia of Sertoli cells from prepubertal rats were grown on Matrigel‐coated millipore filters for short‐circuit current (Isc) measurements. Under basal conditions, these epithelia exhibited a ‘zero’ transepithelial potential difference, a ‘zero’ short‐circuit current and a transepithelial resistance of 60 Ω cm2. Forskolin (100 μm) and 8‐(4‐chlorophenylthio)‐cAMP (cpt‐cAMP) (100 μm) added to the apical side stimulated the Isc (forskolin, peak ΔIsc= 1.32 ± 0.16 μA cm−1; cpt‐cAMP, peak ΔIsc= 0.88 ± 0.16 μA cm−2). ATP (100 μm) added apically elicited a Isc response (peak ΔIsc= 6.45 ± 0.28 μA cm−2) which was similar in magnitude to that of 1 μm thapsigargin (peak ΔIsc= 6.09 ± 0.44 μA cm−2). The potency of the responses to other nucleotides: UTP ≥ ATP > ADP >> AMP = adenosine indicates the involvement of a mixture of P2Y receptors. Removal of extracellular Cl− and HCO3− reduced the Isc response to ATP by 70 % and 40 %, respectively. Removal of K+ had no effect, whereas removal of Na+ attenuated the Isc response. The response to ATP was insensitive to agents known to block anion secretion (except apical diphenylamine‐2‐carboxylate (DPC) and DIDS). The resistance to perturbation by pharmacological agents may be a unique property of the seminiferous epithelium. Whole‐cell current recordings in cultured rat Sertoli cells demonstrated a DIDS‐sensitive outwardly rectifying Cl− conductance with activating and inactivating characteristics at depolarizing and hyperpolarizing voltages, respectively. The stimulation of electrogenic ion transport by ATP may be part of a complex mechanism regulating fluid secretion by the testis. Cultured Sertoli cell epithelia are shown to provide a useful model to investigate transepithelial transport in the seminiferous epithelium.