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

1. Cultured epithelia of Sertoli cells from prepubertal rats were grown on Matrigel-coated millipore filters for short-circuit current (I,,) measurements. Under basal conditions, these epithelia exhibited a 'zero' transepithelial potential difference, a 'zero' short-circuit current and a transepithelial resistance of 60 Omega cm(2). 2. Forskolin (100 mu M) and 8-(4-chlorophenylthio)-cAMP (cpt-cAMP) (100 mu M) added to the apical side stimulated the I-sc (forskolin, peak Delta I-sc = 1.32 +/- 0.16 mu A cm(-1); cpt-cAMP, peak Delta I-sc = 0.88 +/- 0.16 mu A cm(-2)). 3. ATP (100 mu M) added apically elicited a I-sc response (peak Delta I-sc = 6.45 +/- 0.28 mu A cm(-2)) which was similar in magnitude to that of 1 mu M thapsigargin (peak Delta I-sc = 6.09 +/- 0.44 mu A cm-2). The potency of the responses to other nucleotides: UTP greater than or equal to ATP > ADP much greater than AMP = adenosine indicates the involvement of a mixture of P2Y receptors. 4. Removal of extracellular Cl- and HCO3- reduced the I-sc response to ATP by 70% and 40%, respectively Removal of K+ had no effect, whereas removal of Na+ attenuated the I-sc response. 5. 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. 6. 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. 7. 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.