Kuriyama S, Yoshimura N, Ohuchi T, Tanihara H, Ito S, Honda Y. Neuropeptide-induced cytosolic Ca2+ transients and phosphatidylinositol turnover in cultured human retinal pigment epithelial cells.
Brain Res 1992;
579:227-33. [PMID:
1628211 DOI:
10.1016/0006-8993(92)90055-e]
[Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Neuropeptide-induced mobilization of cytosolic free Ca2+ concentration ([Ca2+]i) and phosphatidylinositol (PI) turnover in cultured human retinal pigment epithelial (RPE) cells were studied and their temporal relationship was compared. After RPE cells were loaded with fura-2/AM, [Ca2+]i was analyzed using a digital imaging microscopy system. Bombesin-related peptides which include bombesin, neuromedin B, and neuromedin C induced significant [Ca2+]i transients in RPE cells, whereas other neuropeptides, neuropeptide Y, vasoactive intestinal polypeptide (VIP), and substance P were not effective to produce [Ca2+]i transients. The percentage of reactive cells which showed positive [Ca2+]i transients induced by bombesin-related peptides was around 50%. Bombesin (1 microM) showed a peak concentration of 663 +/- 27.0 nM (mean +/- S.E.M., n = 61), neuromedin B (1 microM), 327 +/- 28.7 nM (mean +/- S.E.M., n = 38), and neuromedin C (1 microM), 357 +/- 22.7 nM (mean +/- S.E.M., n = 32). Ca2+ transients occurred within 30 s and lasted less than 5 min after the application of the neuropeptides. Chelation of the extracellular Ca2+ by EGTA significantly shortened the total time of [Ca2+]i transients induced by the above. The measurements of phosphoinositides in RPE cells revealed that neuropeptide-induced PI turnover was as quick as [Ca2+]i transients. Inositol biphosphate (IP2) and inositol triphosphate (IP3) in RPE cells showed transient increases at 15 s after the stimulation by bombesin-related peptides. These data show that changes in [Ca2+]i and PI turnover are directly linked and both are important in the signal transduction system of bombesin-related peptides in RPE cells. The data also suggest that bombesin-related peptides may play some possible roles in RPE cells.
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