Calcium signals from intact rabbit ciliary epithelium observed with confocal microscopy.

PURPOSE: We investigated patterns of evoked calcium signals to learn about the function of the calcium second messenger system in ciliary epithelium.

METHODS

Isolated infact ciliary processes were loaded with fluo-3/AM and observed with a Bio-Rad MRC-600 laser scanning confocal imaging system, before, during, and after perfusion with catecholamines, cholinergic agents, and autocoids.

RESULTS

One microM acetylcholine (ACH) and 10 microM carbachol (CARB) induced an atropine-sensitive increase in intracellular free calcium ion concentration ([Ca2+]i), considerably greater in NPE than in PE. 10 microM epinephrine (EPI) and 100 microM phenylephrine (PHE) increased [Ca2+]i in NPE and PE, in this case PE > NPE. These effects were blocked by prazosin. 10 mM caffeine (CAF) increased of [Ca2+]i in NPE and PE (NPE > PE) and sometimes produced very slow oscillations with an interval of 10 to 25 s. Prior administration of CAF strongly suppressed the effects of ACH, CARB, EPI, PHE, histamine, and adenosine 5-triphosphate (ATP). One hundred microM ryanodine (RYA) or thapsigargin (TG) increased [Ca2+]i in NPE and PE (NPE > PE).

CONCLUSIONS

In the ciliary epithelium: (1) different patterns of evoked transients and oscillations of calcium were seen in response to agonists; (2) NPE appeared to contain a predominance of muscarinic receptors, while the PE is dominated by alpha 1-adrenergic receptors and (3) the increase in [Ca2+]i by CAF or RYA or TG in either cell layer and the blocking effects of these agents upon agonist, evoking increases in [Ca2+]i, suggested involvement of both the cyclic adenosine diphosphate ribose and the inositol 1, 4, 5 triphosphate (InsP3) systems in the regulation of intracellular calcium.