Am. J. Respir. Cell Mol. Biol., Volume 25, Number 4, October, 2001 447-456

Fetal Alveolar Epithelial Cells Contain [D-Ala²]-Deltorphin I-like Immunoreactivity
- and µ-Opiate Receptors Mediate Opposite Effects in Developing Lung

Mary E. Sunday, Kathleen J. Haley, Rodica L. Emanuel, John S. Torday, Nithiananthan Asokananthan, Kristan A. Sikorski, Ikuo Tooyama, Hiroshi Kimura, Tindaro Renda, and Vittorio Erspamer

Departments of Pathology, Children's Hospital, Brigham & Women's Hospital, and Harvard Medical School; Department of Medicine, Brigham & Women's Hospital and Harvard Medical School; Department of Medicine, Children's Hospital and Harvard Medical School, Boston, Massachusetts; Department of Pediatrics, University of California at Los Angeles, Los Angeles, California; Department of Anatomy, Shiga University of Medical Science, Otsu, Shiga, Japan; and Institute of Human Anatomy and Emeritus of Medical Pharmacology, University La Sapienza, Rome, Italy

Opiate-like peptides can regulate many cellular functions. We now map [D-Ala²]deltorphin I (DADTI)-like immunoreactivity (DADTI-LI) in developing mouse lung and analyze potential functional roles. Most DADTI-LI-positive cells were alveolar cells negative for prosurfactant protein (proSP)-C immunoreactivity. Peak numbers of DADTI-LI-positive cells occurred on embryonic Day 18, decreasing postnatally. To analyze developmental effects of DADTI, e17-18 lung explants were treated with [D-Ala²]deltorphin II (DADTII, soluble DADTI analogue, -receptor-specific) versus dermorphin (µ-receptor-specific). Type II pneumocyte differentiation, assessed by [³H]choline incorporation into saturated phosphatidylcholine and proSP-C immunostaining, was inhibited by DADTII but stimulated by dermorphin. Cell proliferation, measured as [³H]-thymidine incorporation and proliferating cell nuclear antigen immunostaining, was stimulated by DADTII and inhibited by dermorphin. All effects were dose-dependent. DADTII-inhibited choline incorporation was reversed by the -blocker, naltrindole. Unexpectedly, DADTII-stimulated thymidine incorporation was augmented by naltrindole and reversed by naloxone (µ-blocker). Although dermorphin-stimulated choline incorporation was appropriately blocked by binaltorphimine, dermorphin-inhibited thymidine incorporation was reversed by , -, or µ-blockers. The - and µ-receptor messenger RNAs occurred pre- and postnatally, whereas -receptor transcripts occurred mainly prenatally. All three receptor proteins were present in epithelial and mesenchymal cells in e18 lung. Thus, DADTI-LI from proSP-C-immunonegative alveolar cells could regulate development via both direct and indirect effects involving multiple opiate receptors.