Electrophysiological properties of testosterone-secreting cells studied with patch-clamp techniques- a comparison with neurosecretion.

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The testosterone-secreting cells (Leydig cells) in adult mice were isolated mechanically by perfusing intertubular spaces of testes with physiological saline. Perfusates were collected in recording chamber and the Leydig cells were identified by their morphological characteristics (diameter 13-20 <micrn>m,bright cell-border, occasionally,clustered. Indentification was confirmed reliable by the specific staining of 3<beta>-hydroxysteroid dehydrogenase.The whole-cell membranes of Leydig cells were voltage-clamped with patch-electrodes. The holding potential was -80--95 mV and the external saline contained 126 mM NaCl, 5 mM KCl and 10 mM CaCl_2. Depolarization over -40 mV evoked inward currents which decayed completely during 150 msec stimuli. The inward currents were identified as Ca^<2+>-carried current, since replacement of external Ca^<2+> with Mn^<2+> reversibly diminished the current whereas Ba^<2+> or Sr^<2+> substituted for Ca^<2+> . No measurable outward currents were evoked by the depolarization up to +40 mV. The Ca^<2+> channels may be activated by physiological changes in membrane potential, leading to an influx of Ca^<2+>.Leydig cells within a cluster possessed distinct intercellular couplings. The mean coupling ratio obtained by applying two patch electrodes to a pair of cells was 0.84. Transfer or injected dye (Lucifer Yellow) to adjacent cells was also confirmed. Intercellular coupling may paly a role in synchronizing or intensifying the endocrine activities of Leydig cells located within a cluster.